Niu Xiaowei, Feng Yanyan
Zhengzhou Railway Vocational Technical College, Zhengzhou, 450052, China.
Henan Industry and Trade Vocational College, Zhengzhou, 451191, China.
J Mol Model. 2024 Jun 14;30(7):211. doi: 10.1007/s00894-024-06011-1.
In this paper, the effects of torsional deformation on the electronic properties of intrinsic WSe system and Ca-adsorbed WSe system were systematically studied by first-principles method. The results show that Ca can be stably adsorbed on the vacancy (H site) of WSe surface in all deformation systems, and the adsorption energy of the system without deformation is the highest. Intrinsic WSe is a semiconductor with a direct band gap of 1.53 eV. The torsional deformation makes WSe change from a direct band gap semiconductor to an indirect band gap semiconductor and finally to a metal property. The adsorption of Ca makes the conduction band of WSe move down and increases the number of peaks in the conduction band region. The new density of state peaks are mainly derived from the contribution of W-d, Se-p, and d orbitals of adsorbed atoms in each adsorption system. Mulliken charge analysis shows that Ca transfers most of the valence electrons to the substrate, and the torsional deformation changes the amount of transferred charge. The twist deformation reduces the diffusion barrier of Ca on WSe surface from 0.20 to 0.14 eV. The above results provide a basis for the improved application of WSe in ion batteries.
In this study, all the first-principles calculations are based on Materials Studio 8.0 software package. The generalized gradient approximation (GGA) functional Perdew-Burke-Ernzerhof (PBE) is used for the electron exchange correlation interactions in all systems. The optimization algorithm uses Broyden-Fletcher-Goldfarb-Shanno (BFGS) to optimize the model structure and calculate the energy. The measured cutoff energy is optimized to 450 eV, and the radius of the vacuum layer in the Z-axis direction is 20 Å. The K-point of 7 × 7 × 1 is selected by Monkhorst-Pack method. The structural optimization criterion is selected, the convergence radius of the force is 0.01 eV/Å, and the displacement radius between atoms is within 0.001 Å distance. The energy convergence radius of each atom is less than 1.0 × 10 eV/atom.
本文采用第一性原理方法系统研究了扭转变形对本征WSe体系和Ca吸附WSe体系电子性质的影响。结果表明，在所有变形体系中，Ca均可稳定吸附在WSe表面的空位（H位）上，且未变形体系的吸附能最高。本征WSe是一种直接带隙为1.53 eV的半导体。扭转变形使WSe从直接带隙半导体转变为间接带隙半导体，最终转变为金属性质。Ca的吸附使WSe的导带下移，并增加了导带区域的峰数。新的态密度峰主要来源于各吸附体系中W-d、Se-p和吸附原子的d轨道的贡献。Mulliken电荷分析表明，Ca将大部分价电子转移到基底上，扭转变形改变了转移电荷量。扭转变形将Ca在WSe表面的扩散势垒从0.20 eV降低到0.14 eV。上述结果为WSe在离子电池中的改进应用提供了依据。
在本研究中，所有第一性原理计算均基于Materials Studio 8.0软件包。所有体系中的电子交换关联相互作用均采用广义梯度近似（GGA）泛函Perdew-Burke-Ernzerhof（PBE）。优化算法采用Broyden-Fletcher-Goldfarb-Shanno（BFGS）来优化模型结构并计算能量。将测量的截止能量优化为450 eV，Z轴方向真空层的半径为20 Å。采用Monkhorst-Pack方法选取7×7×1的K点。选择结构优化准则，力的收敛半径为0.01 eV/Å，原子间的位移半径在0.001 Å距离内。每个原子的能量收敛半径小于1.0×10 eV/原子。
