Ductile-brittle transition of open-cell nanoporous Cu in tension: A reliance of specific surface area
作者：
Wang, L.;Bi, W. B.;Deng, L.;Xiao, S. F.;Li, B.;...
期刊：
Scripta Materialia ,2020年175:43-48 ISSN：1359-6462
通讯作者：
Zhang, X. M.;Tang, J. F.
作者机构：
[Zhang, XM; Tang, J. F.; Bi, W. B.; Zhang, X. M.; Deng, L.; Wang, L.] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Li, B.; Deng, X. L.] China Acad Engn Phys, Inst Fluid Phys, Natl Key Lab Shock Wave & Detonat Phys Res, Mianyan 621900, Peoples R China.;[Xiao, S. F.] Hunan Univ, Coll Phys & Micro Elect, Changsha 410082, Hunan, Peoples R China.;[Hu, W. Y.] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, XM; Tang, JF] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
关键词：
Nanoporous;Uniaxial tension;Ductile-brittle transition;Dislocation networks
摘要：
We report the ductile-brittle transitions and their reliances on specific surface area (gamma), for the bicontinuous and open-cell nanoporous (NP) Cu in tension, using molecular dynamics simulations. With an increase of gamma, NP Cu undergo the first ductile-to-brittle (gamma <= 2.13 nm(-1)) and subsequent brittle-to-ductile (gamma <= 2.13 nm(-1)) transitions. Two different plasticity modes are governing such two ductile-brittle transitions: dislocation activities inhibition for the former and dislocation networks formation contributes to the latter. Serving as the origin of dislocations/stacking faults, the surface characteristic plays a key role in such ductile-brittle transition and deformation modes. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
语种：
英文
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Pt/Au(111)表面合金电化学稳定性的第一性原理研究
作者：
宋明可;刘迅林;谢先茂;邓磊;汤剑锋
期刊：
云南化工 ,2019年46(1):31-33 ISSN：1004-275X
作者机构：
湖南农业大学理学院,湖南长沙,410128;[汤剑锋; 宋明可; 邓磊; 刘迅林; 谢先茂] 湖南农业大学
关键词：
合金;溶解势;稳定性;密度泛函理论
摘要：
利用密度泛函理论（DFT）对Pt/Au （111）表面合金的电化学稳定性进行了初步研究。形成能计算结果表明,Au与Pt不易在块体中形成合金,但能在Pt （111）面形成表面合金。溶解电位计算结果进一步表明,Pt/Au （111）面上Pt原子的溶解电位与其第一近邻Au原子数有很好的线性关系,而Au对第二近邻及更远近邻的Pt溶解电位的影响可忽略。这些结果意味着可建立表面配位环境与表面原子溶解电位间的标度关系,为揭示表面合金的"结构-电化学稳定性"构型关系奠定了基础。
语种：
中文
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Orientation and grain-boundary dependence of shock-induced plasticity and transformation in nanocrystalline Ti
作者：
Wang, L.;Li, B.;Deng, X. L.;Jian, W. R.;Shang, M.;...
期刊：
PHYSICAL REVIEW B ,2019年99(17):174103 ISSN：2469-9950
通讯作者：
Zhang, X. M.
作者机构：
[Shang, M.; Zhang, X. M.; Deng, L.; Wang, L.; Tang, J. F.] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Li, B.; Deng, X. L.] China Acad Engn Phys, Natl Key Lab Shock Wave & Detonat Phys Res, Inst Fluid Phys, Mianyan 621900, Peoples R China.;[Jian, W. R.] Univ Calif Santa Barbara, Dept Mech Engn, Santa Barbara, CA 93106 USA.;[Hu, W. Y.] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, X. M.] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
摘要：
The plasticity and α→ω transformation are important for the toughness and ductility of hcp titanium under shock loading. However, three questions remain outstanding: (i) what mechanisms govern the plasticity and transformation, (ii) how does the microstructure, i.e., grain boundaries (GBs) and crystallographic orientations, affect them, and (iii) does the transformation take place dependent on the plasticity, such as dislocation slips? We conduct large-scale nonequilibrium molecular dynamics simulations to study shock-induced plasticity and phase transformation in hexagonal columnar nanocrystalline Ti. Significant anisotropy and strong dependence on crystallographic orientation are presented during shock-induced plasticity and phase transformation. The shock first prompts “heterogeneous” dislocation slips and 90∘ lattice reorientation, via coupling deformation twinning and slips. Then, the on-going plastic deformation induces a “heterogeneous” α→ω phase transformation at lower impact velocities or a “homogeneous” solid-state disordering at higher impact velocities. The phase transformation mostly obeys the TAO-1 pathways originated from GBs, while a few of them are governed by Silcock mechanisms within the grains. The TAO-1 and Silcock-governed transformations stem from the emission and propagation of basal-prismatic and prismatic stacking faults, respectively. At the release/tension stage, a ω→α transformation occurs, acting as the reversed process of the α→ω transformation at the compression stage. Meanwhile, structural recovery and spallation initiate in the extending tension area induced by the release fans. Serving as the nucleation of the plasticity, phase transformation, and spallation, GBs play the key role during the loading.
语种：
英文
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Theoretical design of porphyrin dyes with electron-deficit heterocycles towards near-IR light sensitization in dye-sensitized solar cells
作者：
Li, Wei;Ren, Wenhui;Chen, Zhi;Lu, Teng-Fei* ;Deng, Lei;...
期刊：
Solar Energy ,2019年188:742-749 ISSN：0038-092X
通讯作者：
Zhang, Xingming;Wang, Liang;Lu, Teng-Fei
作者机构：
[Chen, Zhi; Deng, Lei; Zhang, XM; Wang, Liang; Tang, Jianfeng; Li, Wei; Ren, Wenhui; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Bai, Fu-Quan; Lu, Teng-Fei] Jilin Univ, Inst Theoret Chem, Int Joint Res Lab Nanomicro Architecture Chem, Changchun 130023, Jilin, Peoples R China.
通讯机构：
[Zhang, XM; Wang, L] H;[Lu, Teng-Fei] J;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Jilin Univ, Inst Theoret Chem, Int Joint Res Lab Nanomicro Architecture Chem, Changchun 130023, Jilin, Peoples R China.
关键词：
Absorption spectrum;Charge transfer;Density functional theory;Dye-sensitized solar cells;Electronic structure
摘要：
We develop a series of porphyrin sensitizers with electron-deficit heterocycles based on the well-known YD2-o-C8 dye for application in dye-sensitized solar cells with the help of ab initio density functional theory calculations and quantum dynamics simulation based on the tight-binding extended Hückel Hamiltonian at the semiempirical level. The calculation results show that introduction of electron-deficit heterocycles into the porphyrin dyes can remarkably red-shift and broaden the Q band of the absorption spectrum and extend the coverage into near-infrared region, improving the light-harvesting ability. The key parameters influencing the photocurrent and photovoltage performance such as maximum short-circuit photocurrent (JSC max), intramolecular charge transfer, interface electron injection, and the shift of TiO2 conduction band edge (ΔECB) are superior to YD2-o-C8 dye. Therefore, the designed sensitizers would be promising candidate for utilization in dye-sensitized solar cells. © 2019 International Solar Energy Society
语种：
英文
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Intrinsic strain-induced segregation in multiply twinned Cu-Pt icosahedra
作者：
Deng, Lei;Liu, Xunlin;Zhang, Xingming* ;Wang, Liang;Li, Wei;...
期刊：
PHYSICAL CHEMISTRY CHEMICAL PHYSICS ,2019年21(9):4802-4809 ISSN：1463-9076
通讯作者：
Zhang, Xingming;Tang, Jianfeng
作者机构：
[Zhang, XM; Tang, Jianfeng; Deng, Lei; Li, Wei; Liu, Xunlin; Wang, Liang; Song, Mingke; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, Huiqiu; Hu, Wangyu] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.;[Xiao, Shifang] Hunan Univ, Sch Phys & Elect, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, XM; Tang, JF] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
摘要：
We present an atomistic simulation study on the compositional arrangements throughout Cu-Pt icosahedra, with a specific focus on the effects of inherent strain on general segregation trends. The coexistence of radial and site-selective segregation patterns is found in bimetallic nanoparticles for a broad range of sizes and compositions, consistent with prior analytical and atomistic models. Through a thorough comparison between the composition patterns and strain-related patterns, it is suggested that the presence of gradient and site-selective segregation is natural to largely relieve the inherent strain by preferential segregation of big atoms at tensile sites and vice versa, as previously hypothesized in the literature. Analogous to the case of single crystal particles, Cu-rich surface and damped oscillations can also be found in the outer shells of icosahedra, which are dominated by the lowering of both the surface energy and the chemical energy. The thermodynamic stability of segregated icosahedra is similar to segregated cuboctahedra but higher than disordered bulk alloys, validating prior thinking that element segregation driven by strain relief can extend the stability range of multiply-twinned nanoparticles. Our work sheds new light on understanding strain-induced segregation in multiply-twinned nanosystems that have elements with large lattice mismatch and strong alloying ability. © the Owner Societies.
语种：
英文
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表面Au修饰Pt纳米晶体电化学稳定性的第一性原理研究
作者：
宋明可;刘迅林;谢先茂;邓磊;汤剑锋
期刊：
湖南文理学院学报(自然科学版) ,2019年31(02):34-37 ISSN：1672-6146
作者机构：
湖南农业大学理学院,湖南长沙, 410128;[汤剑锋; 宋明可; 邓磊; 刘迅林; 谢先茂] 湖南农业大学
关键词：
纳米粒子;溶解电位;稳定性;密度泛函理论
摘要：
利用密度泛函理论(DFT)对表面未/金修饰的截角八面体铂纳米粒子的电化学稳定性进行了对比研究.溶解电位计算结果表明:纯Pt纳米粒子的表面棱边位置配位高度不饱和,电化学稳定性较差;对于Pt177Au24、Pt141Au60和Pt135Au66三个表面金修饰的纳米粒子,发现Pt135Au66纳米粒子有更好的电化学稳定性且对其平整表面活性位点的催化性能没有影响.这些结果意味着以痕量Au表面掺杂提高Pt纳米粒子的电化学稳定性是可行的策略.
语种：
中文
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Anharmonicity Extends Carrier Lifetimes in Lead Halide Perovskites at Elevated Temperatures.
作者：
Li, Wei;Vasenko, Andrey S.;Tang, Jianfeng* ;Prezhdo, Oleg V.*
期刊：
Journal of Physical Chemistry Letters ,2019年10(20):6219-6226 ISSN：1948-7185
通讯作者：
Tang, Jianfeng;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Vasenko, Andrey S.] Natl Res Univ Higher Sch Econ, Moscow 101000, Russia.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Tang, Jianfeng] H;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
关键词：
Carrier lifetime;Density functional theory;Energy harvesting;Lead compounds;Molecular dynamics;organic-inorganic materials;Photocatalytic activity;Solar energy;Temperature distribution;Electron-hole recombination;Electronic subsystems;Equilibrium geometries;Hybrid organic-inorganic;In-depth understanding;Nonadiabatic molecular dynamics;Optoelectronic applications;Temperature dependence;Perovskite
摘要：
Lead halide perovskites constitute a very promising class of materials for a broad range of solar and optoelectronic applications. Perovskites exhibit many unusual properties, and recent experiments demonstrate an unusual temperature dependence of charge carrier lifetimes. Focusing on the all-inorganic CsPbBr3, and using a combination of ab initio nonadiabatic molecular dynamics and time-domain density functional theory, we demonstrate that the unconventional behavior arises because of a highly anharmonic nature of atomic motions in perovskites. As temperature increases, perovskite structure undergoes a notable deformation, reflected in tilting of octahedral units, and experiences large-scale anharmonic movements away from the equilibrium geometry. As a result, the electronic energy gap increases, and phonon-induced loss of coherence within the electronic subsystem accelerates. These two factors slow down nonradiative electron-hole recombination, which constitutes the main limitation on efficiencies of perovskite solar, optical, and electronic devices. The increase of charge carrier lifetimes with temperature is particularly beneficial in applications, because materials heat up, for instance, from sunlight during solar energy harvesting. The behavior of the all-inorganic halide perovskite investigated here is different from that of hybrid organic-inorganic perovskites, which exhibit additional disorder associated with reorientations of the asymmetric organic cations. The reported simulations generate an in-depth understanding of the unusual properties of inorganic perovskites, relevant for photocatalytic, photovoltaic, electronic, and optical applications. © 2019 American Chemical Society.
语种：
英文
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Phosphorus and oxygen co-doped composite electrode with hierarchical electronic and ionic mixed conducting networks for vanadium redox flow batteries
作者：
Ling, Wei;Wang, Zhi-An;Ma, Qiang;Deng, Qi;Tang, Jian-Feng;...
期刊：
Chemical Communications ,2019年55(77):11515-11518 ISSN：1359-7345
通讯作者：
Wu, Xiong-Wei;Yue, Jun-Pei;Guo, Yu-Guo
作者机构：
[Ma, Qiang; Deng, Lei; Wu, Xiong-Wei; Tang, Jian-Feng; Ling, Wei; Deng, Qi] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Wang, Zhi-An] Cent S Univ, Sch Chem & Chem Engn, Changsha 410083, Hunan, Peoples R China.;[Zhu, Liang-Hong] Shenzhen Polytech, Automot & Transportat Engn, Shenzhen 518055, Guangdong, Peoples R China.;[Yue, Jun-Pei; Guo, Yu-Guo] Chinese Acad Sci, CAS Key Lab Mol Nanostruct & Nanotechnol, Inst Chem, Beijing 100190, Peoples R China.
通讯机构：
[Wu, Xiong-Wei] H;[Yue, JP; Guo, YG] C;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Chinese Acad Sci, CAS Key Lab Mol Nanostruct & Nanotechnol, Inst Chem, Beijing 100190, Peoples R China.
摘要：
The hierarchical electronic and ionic mixed conducting networks build in graphite felt electrodes possess excellent electrocatalytic activity and faster electronic and ionic conduction, resulting in an enhanced energy efficiency of vanadium redox flow batteries with durable life for 1000 cycles and a high discharge capacity of 10.1 A h L-1 at a current density of 350 mA cm-2. This journal is © The Royal Society of Chemistry.
语种：
英文
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Influence of Defects on Excited-State Dynamics in Lead Halide Perovskites: Time-Domain ab Initio Studies
作者：
Li, Wei* ;Long, Run* ;Tang, Jianfeng* ;Prezhdo, Oleg V.*
期刊：
Journal of Physical Chemistry Letters ,2019年10(13):3788-3804 ISSN：1948-7185
通讯作者：
Li, Wei;Tang, Jianfeng;Long, Run;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei; Li, W] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Long, Run] Beijing Normal Univ, Minist Educ, Key Lab Theoret & Computat Photochem, Coll Chem, Beijing 100875, Peoples R China.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Li, W; Tang, JF] H;[Long, Run] B;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Beijing Normal Univ, Minist Educ, Key Lab Theoret & Computat Photochem, Coll Chem, Beijing 100875, Peoples R China.
关键词：
Density functional theory;Energy dissipation;Grain boundaries;Laser spectroscopy;Lead compounds;Molecular dynamics;Perovskite;Perovskite solar cells;Point defects;Quantum theory;Ab initio density functional theories (DFT);Ab initio simulations;Excited-state dynamics;Halide perovskites;Nonadiabatic molecular dynamics;Photocatalytic application;Recent researches;Time-resolved spectroscopy;Excited states
摘要：
This Perspective summarizes recent research into the excited-state dynamics in lead halide perovskites that are of paramount importance for photovoltaic and photocatalytic applications. Nonadiabatic molecular dynamics combined with time-domain ab initio density functional theory allows one to mimic time-resolved spectroscopy experiments at the atomistic level of detail. The focus is placed on realistic aspects of perovskite materials, including point defects, surfaces, grain boundaries, mixed stoichiometries, dopants, and interfaces. The atomistic description of the quantum dynamics of electron and hole trapping and recombination, provided by the time-domain ab initio simulations, generates important insights into the mechanisms of charge and energy losses and guides the development of high-performance perovskite solar cell devices. © 2019 American Chemical Society.
语种：
英文
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Revealing the Reaction Mechanism of Sodium Selenide Confined within a Single-Walled Carbon Nanotube: Implications for Na-Se Batteries
作者：
Wang, Liang;Zhang, Xingming;Deng, Lei;Tang, Jianfeng;Deng, Huiqiu* ;...
期刊：
ACS Applied Materials & Interfaces ,2019年11(5):4995-5002 ISSN：1944-8244
通讯作者：
Deng, Huiqiu;Hu, Wangyu;Liu, Zhixiao
作者机构：
[Deng, Lei; Tang, Jianfeng; Wang, Liang; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, Huiqiu] Hunan Univ, Sch Phys & Elect, Changsha 410082, Hunan, Peoples R China.;[Hu, Wangyu; Liu, Zhixiao] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Deng, Huiqiu; Hu, WY; Liu, ZX] H;Hunan Univ, Sch Phys & Elect, Changsha 410082, Hunan, Peoples R China.;Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
关键词：
Na-Se battery;ab initio molecular dynamics;conductivity;density functional theory computation;nanoconfinement;polaron;reaction mechanism
摘要：
The sodium-selenium (Na-Se) battery is a competitive candidate as the practical next-generation energy storage device. A Na 16 Se 8 cluster confined within a (10, 10) single-walled carbon nanotube is constructed to reveal the nanoconfinement effect on the reaction mechanism of the Na-Se battery cathode. It is found that the nanoconfinement can enhance the electronic conductivity of Na x≥12 Se 8 nanostructures because itinerant electrons appear under this condition. During desodiation, polyselenide chains grow longer and the intermediate products become insulators for transferring electrons. However, hole polarons have the potential to act as charge carriers in Na x≤10 Se 8 nanostructures. The open-circuit voltage profile is plotted, and the voltage window is 1.67 ≤ U ≤ 1 V. After the first charge cycle, the cathode cannot discharge to Na 16 Se 8 , but the reversible specific capacity can still arrive at 302 mA h/g of the cathode composite. © 2019 American Chemical Society.
语种：
英文
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Investigation of the interstitial oxygen behaviors in vanadium alloy: A first-principles study
作者：
Zhang, Xingming;Li, Yifan;He, Qiaoling;Li, Ruilian* ;Deng, Lei;...
期刊：
Current Applied Physics ,2018年18(2):183-190 ISSN：1567-1739
通讯作者：
Li, Ruilian
作者机构：
[Deng, Lei; Li, Yifan; Tang, Jianfeng; Liu, Xunlin; Wang, Liang; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Li, Ruilian; He, Qiaoling] Hunan Agr Univ, Coll Agr, Changsha 410128, Hunan, Peoples R China.;[Deng, Huiqiu] Hunan Univ, Sch Phys & Elect, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China.;[Hu, Wangyu] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Li, Ruilian] H;Hunan Agr Univ, Coll Agr, Changsha 410128, Hunan, Peoples R China.
关键词：
Vacancy-impurity binding;Vanadium alloys;First-principles calculations;Diffusion;Precipitate
摘要：
This study aims at characterizing the interstitial Oxygen (O) behaviors in the Vanadium (V) Alloy by means of the first-principles calculations. For this, the interations between vacancy (Vac) and O interstitil atom are studied in detail to obtain the binding energies and stable structures of the complexes. It can be seen that monovacancy binding with two O atoms occupied the opposing octahedral stie are particularly stable, and is liable to form VacO2 cluster in the V alloys. According to the mass action analysis, the predicted temperature dependence of the concentration for VacOn complexes are presented. Apart from monovacancy, we also consider the trapping behavior of vacancy cluster on the O atoms. The results also prove that one vacancy can trap two O atoms in the V alloys. Based the diffusion theory, we obtain the diffusion coefficients as a function of temperature with or without the vacancy effect in the V alloys. The predicted O diffusion coefficients in defect-free V alloys from our first-principles calculations are in excellent ageement with the experimental data, meanings that the vacancy-limited mechanism does not play the key role for O diffusion in V alloys. Regarding the interactions between vacancy, solutes and O atom, combining with the diffusion barriers of O affected by vacancy and solute, we infer the formation mechanism of the precipitates in the V alloys. © 2017 Elsevier B.V.
语种：
英文
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The effect of solutes on the precipitate/matrix interface properties in the Vanadium alloys: A first-principles study
作者：
Zhang, Xingming;Deng, Lei;Wang, Liang* ;Tang, Jianfeng;Deng, Huiqiu;...
期刊：
计算材料学(英文) ,2018年153:113-118 ISSN：2057-3960
通讯作者：
Wang, Liang
作者机构：
[Deng, Lei; Tang, Jianfeng; Wang, Liang; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, Huiqiu] Hunan Univ, Sch Phys & Elect, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China.;[Hu, Wangyu] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Wang, Liang] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
关键词：
First-principles calculations;Precipitate/matrix interface;Solute segregation;Vanadium alloys
摘要：
A correct description of the interaction between solutes and interface is the prerequisite for an understanding of the evolution and growth kinetics of precipitate. In this study, we use the first-principles calculations to characterize the solute (Cr, Ti, and Y) behaviors at the TiO-precipitate/V-matrix interface in Vanadium (V) alloys. After obtaining the equilibrium interface structure, the formation heat and segregation energies for solutes (Cr, Ti, and Y) are studied in detail to obtain the site preference and segregation behaviors for solutes in the interface region. We found that solute Ti prefer to the interface site and shows a segregation tendency at the interface. To the contrary, solute Cr and Y prefer to retain in the V matrix. However, from the standpoint of energy, the site preferences for all solutes are extremely weak when no vacancy is introduced to the interface. Considering the vacancy effect, the site preference of solute Y is changing and shows a segregation tendency at the interface. We also calculate the Griffith rupture work to uncover how the solutes influence the interfacial strength with or without the vacancy effect. Solute Cr is favorable for improving the interfacial rupture strength of the V alloys no matter where solute Cr is positioned. As for solute Ti and Y, when solutes are close to the interface, the interface-weakening effect is obvious. The improvement of solutes in interfacial strength is ascribed to the increased the hybridization behaviors between the solute atom and the Ti atoms in the precipitate. © 2018 Elsevier B.V.
语种：
英文
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Surface premelting/recrystallization governing the collapse of open-cell nanoporous Cu via thermal annealing
作者：
Wang, L.;Zhang, X. M.;Deng, L.* ;Tang, J. F.* ;Xiao, S. F.;...
期刊：
PHYSICAL CHEMISTRY CHEMICAL PHYSICS ,2018年20(23):16184-16192 ISSN：1463-9076
通讯作者：
Deng, L.;Tang, J. F.
作者机构：
[Zhang, X. M.; Deng, L.; Tang, J. F.; Wang, L.] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, H. Q.; Xiao, S. F.] Hunan Univ, Coll Phys & Micro Elect, Changsha 410082, Hunan, Peoples R China.;[Hu, W. Y.] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Deng, L; Tang, JF] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
摘要：
We systematically investigate the collapse of a set of open-cell nanoporous Cu (np-Cu) materials with the same porosity and shape but different specific surface areas, during thermal annealing, by performing large-scale molecular dynamics simulations. Two mechanisms govern the collapse of np-Cu. One is direct surface premelting, facilitating the collapse of np-Cu, when the specific surface area is less than a critical value (similar to 2.38 nm(-1)). The other is recrystallization followed by surface premelting, accelerating the sloughing of ligaments and the annihilation of voids, when the critical specific surface area is exceeded. Surface premelting results from surface reconstruction by prompting localized "disordering" and "chaos" on the surface, and the melting temperature reduces linearly with the increase of the specific surface area. Recrystallization is followed by surface premelting as the melting temperature is below the supercooling point, where a liquid is unstable and instantaneously recrystallizes.
语种：
英文
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Promising pyridinium ylide based anchors towards high-efficiency dyes for dye-sensitized solar cells applications: Insights from theoretical investigations
作者：
Lu, Teng-Fei;Li, Wei* ;Chen, Jie;Tang, Jianfeng;Bai, Fu-Quan;...
期刊：
Electrochimica Acta ,2018年283:1798-1805 ISSN：0013-4686
通讯作者：
Zhang, Hong-Xing;Li, Wei
作者机构：
[Bai, Fu-Quan; Lu, Teng-Fei; Zhang, Hong-Xing; Chen, Jie] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.;[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
通讯机构：
[Zhang, Hong-Xing] J;[Li, Wei] H;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
关键词：
Dye-sensitized solar cell;Density function theory;Charge transfer;Anchoring group;Organic dye
摘要：
We theoretically examine a series of anchors for dye-sensitized solar cells application, with particular attention was paid to the potential of novel pyridinium ylide based anchors. The geometrical structure, electronic property, and optical spectrum of the isolated dyes and its interface with TiO2 are analyzed by using quantum chemistry calculations. Quantum dynamics simulation is performed to investigate the interface electron transfer process across the dye/TiO2 interface. The key parameters influencing the short-circuit current and open-circuit voltage are calculated to quantify the performance of different dyes. Our results show that the pyridinium ylide based anchors benefit light-harvesting and improve intramolecular charge transfer character as well as shift up the conduction band edge of TiO2 semiconductor which further increase short-circuit current and open-circuit voltage. Conjugated rhodanime-3-acetic anchor exhibits the enhanced electron injection than the non-conjugated structure due to the more significant donor-acceptor interaction. The simulation performed in this work demonstrates the potential of novel pyridinium ylide based anchors with respect to the traditional carboxylic acid and rhodanime-3-acetic based anchors, reveals the crucial role of local structure variation in the interface electron transfer, and finally guides the design of high-efficiency sensitizer for dye-sensitized solar cells application.
We theoretically examine a series of anchors for dye-sensitized solar cells application, with particular attention was paid to the potential of novel pyridinium ylide based anchors. The geometrical structure, electronic property, and optical spectrum of the isolated dyes and its interface with TiO2 are analyzed by using quantum chemistry calculations. Quantum dynamics simulation is performed to investigate the interface electron transfer process across the dye/TiO2 interface. The key parameters influencing the short-circuit current and open-circuit voltage are calculated to quantify the performance of different dyes. Our results show that the pyridinium ylide based anchors benefit light-harvesting and improve intramolecular charge transfer character as well as shift up the conduction band edge of TiO2 semiconductor which further increase short-circuit current and open-circuit voltage. Conjugated rhodanime-3-acetic anchor exhibits the enhanced electron injection than the non-conjugated structure due to the more significant donor-acceptor interaction. The simulation performed in this work demonstrates the potential of novel pyridinium ylide based anchors with respect to the traditional carboxylic acid and rhodanime-3-acetic based anchors, reveals the crucial role of local structure variation in the interface electron transfer, and finally guides the design of high-efficiency sensitizer for dye-sensitized solar cells application.
语种：
英文
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碳包覆Li3VO4作为锂离子电池负极材料的研究
作者：
张秀梅;周彬;汤剑锋;吴雄伟
期刊：
广州化学 ,2018年43(2):46-51 ISSN：1009-220X
作者机构：
湖南农业大学理学院;[周彬] 中国烟草总公司云南省公司;湖南省银峰新能源有限公司;[吴雄伟; 张秀梅; 汤剑锋] 湖南农业大学
关键词：
溶胶-凝胶法;负极材料;电化学性能
摘要：
采用溶胶-凝胶法合成碳包覆Li3VO4复合材料（Li3VO4/C）,通过X-射线衍射仪（XRD）、扫描电子显微镜（SEM）、热重分析仪（TG）对其进行了表征,探究了该材料作为锂离子电池负极材料的电化学性能。结果表明,该材料具有良好的循环性能和优异的倍率性能。在1.25 C（1 C=400 m Ah/g）的电流密度下,其首次充电比容量为199.6 m Ah/g,循环150次后,其容量保持率为89.2%。此外,在充放电倍率分别为0.5、1、2、5、10 C时,其充电比容量分别为228.7、202、180.5、149.9、116.6 m Ah/g。
语种：
中文
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Influence of an exciton-delocalizing ligand on the structural, electronic, and spectral features of the Cd33S33 quantum dot: insights from computational studies
作者：
Li, Wei* ;Lu, Teng-Fei;Ren, Wenhui;Deng, Lei;Zhang, Xingming;...
期刊：
Journal of Materials Chemistry C ,2018年6(32):8751-8761 ISSN：2050-7526
通讯作者：
Li, Wei;Tang, Jianfeng;Kuznetsov, Aleksey E.
作者机构：
[Deng, Lei; Tang, Jianfeng; Li, Wei; Wang, Liang; Ren, Wenhui; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Li, Wei; Lu, Teng-Fei] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Peoples R China.;[Kuznetsov, Aleksey E.] Univ Sao Paulo SP, Inst Quim, Ave Prof Lineu Prestes 748, BR-05508000 Sao Paulo, SP, Brazil.
通讯机构：
[Li, W; Tang, JF] H;[Li, Wei] J;[Kuznetsov, Aleksey E.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Peoples R China.
关键词：
Binding energy;Cadmium compounds;Charge transfer;Computation theory;Density functional theory;Energy gap;Excited states;Excitons;Ground state;Ligands;Nanocrystals;Optical properties;Solar cells;Computational studies;Electronic band gaps;Excited-state properties;Exciton delocalization;High-energy absorption;Quantum dot transition;Theoretical investigations;Time dependent density functional theory;Semiconductor quantum dots
摘要：
Quantum dot based solar cells have attracted considerable attention owing to the unique geometrical, electronic, and optical properties of quantum dots. Exciton-delocalizing ligands, such as phenyldithiocarbamate, are demonstrated to benefit charge extraction in quantum dot-based solar cells. However, sufficient details of the exciton delocalization mechanism are still lacking. This work reports theoretical investigations concerning the role of the exciton-delocalizing linker for the ground- and excited-state properties of the Cd33S33 quantum dot. We perform density functional theory and time-dependent density functional theory investigations of the Cd33S33 quantum dot functionalized with two hole acceptors: PTC-PTZ, a phenothiazine ligand with the exciton-delocalizing phenyldithiocarbamate linker, and BA-PTZ, phenyldithiocarbamate with the benzoate linker which is not an exciton-delocalizing ligand. Our calculation results find that PTC-PTZ has two binding modes: bidentate binding and flat binding modes, with the latter being more favorable. The phenyldithiocarbamate linker tends to delocalize the charge densities compared to benzoate. For all complexes, solvent increases electronic band gaps and makes quantum dot-to-quantum dot transitions dominate for the high-energy absorption band. Electron density differences between the excited state and the ground state suggest that the exciton-delocalizing PTC-PTZ molecule, especially the flat binding mode, would induce more significant charge transfer in the direction from the quantum dot to the dye. © The Royal Society of Chemistry.
语种：
英文
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Time-Domain ab lnitio Analysis Rationalizes the Unusual Temperature Dependence of Charge Carrier Relaxation in Lead Halide Perovskite
作者：
Li, Wei* ;Tang, Jianfeng;Casanova, David;Prezhdo, Oleg V.*
期刊：
ACS Energy Letters ,2018年3(11):2713-2720 ISSN：2380-8195
通讯作者：
Li, Wei;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Casanova, David] DIPC, Donostia San Sebastian 20018, Euskadi, Spain.;[Casanova, David] IKERBASQUE, Basque Fdn Sci, Bilbao 48013, Euskadi, Spain.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Li, Wei] H;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
摘要：
Increased charge carrier lifetimes at elevated temperatures constitute an intriguing and valuable feature of hybrid organic-inorganic perovskites that are subject to heating in solar energy applications. We rationalize this peculiar behavior at the atomistic level using real-Time time-dependent density functional theory and nonadiabatic molecular dynamics. Focusing on tetragonal MAPbI3, we demonstrate that temperature has different effects on the organic and inorganic subsystems and leads to subtle structural changes, decreasing nonradiative electron-hole recombination. First, charge-phonon interactions are decreased because the libration dynamics of the organic component at higher temperature reduces the oscillation amplitude of the Pb-I lattice that supports electrons and holes. Second, thermal disorder localizes wave functions, reducing the nonadiabatic charge-phonon coupling. Third, tilting of the inorganic octahedra increases the bandgap, extending charge carrier lifetime further. The detailed time-domain atomistic analysis of the uncommon dependence of charge recombination on temperature emphasizes the key role played by the organic cation, establishes important structure-property relationships, provides valuable insights into efficient performance of perovskite solar cells, and highlights factors required to maintain and improve such performance. © 2018 American Chemical Society.
语种：
英文
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Shock wave propagation, plasticity, and void collapse in open-cell nanoporous Ta
作者：
Tang, J. F.;Xiao, J. C.;Deng, L.;Li, W.;Zhang, X. M.* ;...
期刊：
PHYSICAL CHEMISTRY CHEMICAL PHYSICS ,2018年20(44):28039-28048 ISSN：1463-9076
通讯作者：
Zhang, X. M.;Wang, L.
作者机构：
[Li, W.; Zhang, XM; Wang, L.; Xiao, J. C.; Zhang, X. M.; Deng, L.; Tang, J. F.] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Deng, H. Q.; Xiao, S. F.] Hunan Univ, Coll Phys & Micro Elect, Changsha 410082, Hunan, Peoples R China.;[Hu, W. Y.] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Zhang, XM; Wang, L] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.
摘要：
We systematically investigate the wave propagation, plasticity and void collapse, as well as the effects of porosity, specific surface area and impact velocity, in a set of open-cell nanoporous Ta, during shock compression, via performing large-scale non-equilibrium molecular dynamics simulations. The shock wave propagation presents an impedance, sensitive to porosity, but not to specific surface area. Such surprising phenomena are due to the similar sensitivities in density and stress variations to porosity or specific surface area. Upon impact, shock front shapes change from ramped to steep ones, with increasing porosity, specific surface area or impact velocity, owing to the transition from the heterogeneous to homogeneous plasticity along transverse directions. This transition of plasticity arises by (i) the strong impedance on large deformation bands as porosity increases; and (ii) the transition from deformation twinning to dislocation slips, and to amorphization, as the specific surface area or impact velocity increases. Shock-induced plasticity, including their nucleation, growth and interactions, also facilitates the collapse of voids.
语种：
英文
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Influence of Encapsulated Water on Luminescence Energy, Line Width, and Lifetime of Carbon Nanotubes: Time Domain Ab Initio Analysis
作者：
Li, Wei* ;Long, Run;Hou, Zhufeng;Tang, Jianfeng;Prezhdo, Oleg V.*
期刊：
Journal of Physical Chemistry Letters ,2018年9(14):4006-4013 ISSN：1948-7185
通讯作者：
Li, Wei;Prezhdo, Oleg V.
作者机构：
[Tang, Jianfeng; Li, Wei] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Li, Wei] Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.;[Long, Run] Beijing Normal Univ, Minist Educ, Coll Chem, Key Lab Theoret & Computat Photochem, Beijing 100875, Peoples R China.;[Hou, Zhufeng] NIMS, 1-2-1 Sengen, Tsukuba, Ibaraki 3050047, Japan.;[Prezhdo, Oleg V.] Univ Southern Calif, Dept Chem, Los Angeles, CA 90089 USA.
通讯机构：
[Li, Wei] H;[Li, Wei] J;[Prezhdo, Oleg V.] U;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Jilin Univ, Inst Theoret Chem, Lab Theoret & Computat Chem, Changchun 130023, Jilin, Peoples R China.
关键词：
Defects;Density functional theory;Electron diffraction;Electron scattering;Electron-phonon interactions;Electronic properties;Excited states;Luminescence;Molecular dynamics;Molecules;Phonon scattering;Time domain analysis;Yarn;Electron phonon scattering;Excited state lifetimes;Linewidth broadening;Nonadiabatic molecular dynamics;Radial breathing mode;Time dependent density functional theory;Vibrational dynamics;Vibrational properties;Carbon nanotubes
摘要：
In a broad range of applications, carbon nanotubes (CNTs) are in direct contact with a condensed-phase environment that perturbs CNT properties. Experiments show that water molecules encapsulated inside of semiconducting CNTs reduce the electronic energy gap, enhance elastic and inelastic electron-phonon scattering, and shorten the excited-state lifetime. We rationalize the observed effects at the atomistic level using real-time time-dependent density functional theory combined with nonadiabatic molecular dynamics. Encapsulated water makes the nanotube more rigid, suppressing radial breathing modes while enhancing and slightly shifting the optical G-mode. Water screens Coulomb interactions and shifts charge carrier energies and wave functions. The screening, together with distortion of the CNT geometry and lifting of orbital degeneracy, produces a luminescence red shift. Enhanced elastic and inelastic electron-phonon scattering explains line width broadening and shortening of the excited-state lifetime. The influence of water on the CNT properties is similar to that of defects; however, in contrast to defects, water creates no new phonon modes or electronic states in the CNTs. The atomistic understanding of the influence of the condensed-phase environment on CNT optical, electronic, and vibrational properties, and electron-vibrational dynamics guides design of novel CNT-based materials. Copyright © 2018 American Chemical Society.
语种：
英文
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Local identification of chemical ordering: Extension, implementation, and application of the common neighbor analysis for binary systems
作者：
Deng, Lei;Zhang, Xingming;Wang, Liang;Tang, Jianfeng* ;Liu, Zhixiao;...
期刊：
计算材料学(英文) ,2018年143:195-205 ISSN：2057-3960
通讯作者：
Tang, Jianfeng;Hu, Wangyu
作者机构：
[Deng, Lei; Tang, Jianfeng; Wang, Liang; Zhang, Xingming] Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;[Liu, Zhixiao; Deng, Huiqiu; Hu, Wangyu] Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.;[Xiao, Shifang] Hunan Univ, Sch Phys & Elect, Changsha 410082, Hunan, Peoples R China.
通讯机构：
[Tang, Jianfeng; Hu, Wangyu] H;Hunan Agr Univ, Coll Sci, Changsha 410128, Hunan, Peoples R China.;Hunan Univ, Coll Mat Sci & Engn, Changsha 410082, Hunan, Peoples R China.
关键词：
Atomistic simulation;Bulk alloys;Chemical ordering;Nanocrystal alloy
摘要：
The common neighbor analysis (CNA) for binary systems is a promising tool for the identification of chemical ordering in atomic configurations obtained from atomistic simulations. It is an extension of the monatomic CNA by taking the chemical species of common neighbors as an additional criterion and thus can give the individual short-range order for each atom and the long-range order for a block of atoms in binary alloys. The possible shortcoming is also obvious since they only reflect the characteristic arrangement of the nearest neighbors of the reference atom. Here we presented a further extension of the nearest-neighbor binary CNA method to the second-nearest neighbor one. The bulk signatures for the most common ordered structures based on face centered cubic were given, including D1/D7 (Ca<inf>7</inf>Ge/CuPt<inf>7</inf>), “40”(NbP), L1<inf>0</inf>(AuCu), L1<inf>1</inf>(CuPt), L1<inf>2</inf>(AuCu<inf>3</inf>), L1<inf>3</inf>(CuPt<inf>3</inf>), and D0<inf>22</inf>(Al<inf>3</inf>Ti). For these perfect bulk alloys, the extended binary CNA is able to correctly identify all the chemical ordered phases, while the original one fails except for the L1<inf>1</inf>-structure. The types and magnitudes of ordered phases in several examples with some composition- and position-randomness and complexity are analyzed, including Ni/Ni<inf>3</inf>Al composite as well as Cu–Pt and Au–Pd nanoparticles obtained from off-lattice Monte Carlo simulations. It is demonstrated that this extended CNA method shows higher robustness and accuracy relative to the local mixing index or the polyhedral template matching scheme. The algorithm is implemented using Fortran programming language and the codes can be obtained by contacting the authors.<br/> ©2017 Elsevier B.V.
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英文
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