Towards accurate models for amorphous GeTe: Crucial effect of dispersive van der Waals corrections on the structural properties involved in the phase-change mechanism
Towards accurate models for amorphous GeTe: Crucial effect of dispersive van der Waals corrections on the structural properties involved in the phase-change mechanism
复制标题
建立非晶 GeTe 的精确模型：色散范德华校正对相变机制中涉及的结构特性的关键影响
DOI：
10.1103/physrevb.96.184204
复制
发表时间：
2017
影响因子：
3.7
通讯作者：
A. Pradel
中科院分区：
文献类型：
--
作者：
M. Micoulaut;A. Piarristeguy;H. Flores;A. Pradel
研究了货车德瓦耳斯色散修正与密度泛函理论相结合对正则非晶相变材料的影响。密度泛函理论（DFT），使用广义梯度近似，通常无法再现的非晶碲化物的结构，这表现在高估的原子间键距，特别是Ge-Te的一个涉及局部几何形状（四面体或缺陷八面体）。在这里，我们考虑到色散力的半经验的方式，并应用这种DFT模拟非晶碲化锗。我们获得了大幅改善的模拟结构因子和配对相关函数，现在再现实验同行具有前所未有的准确性，包括最近的部分贡献，从异常X射线散射和X射线吸收。相应的结构的详细分析表明，色散校正减少了Ge-Te键长，增加了四面体锗的分数，并减少了异极的所谓的四重ABAB环的存在。考虑到这些结构特征已被强调为理解相变机制的核心，目前的结果挑战了我们目前对晶体到非晶转变的理解。DOI：
The effect of van der Waals dispersion correction in combination with density functional theory is investigated on a canonical amorphous phase-change material. Density functional theory (DFT), using the generalized gradient approximation, usually fails to reproduce the structure of amorphous tellurides, which manifests by an overestimation of the interatomic bond distances, and particularly the Ge-Te one involved in local geometries (tetrahedral or defect octahedral). Here, we take into account dispersion forces in a semiempirical way and apply such DFT simulations to amorphous GeTe. We obtain a substantial improvement of the simulated structure factor and pair-correlation function, which now reproduce the experimental counterparts with an unprecedented accuracy, including on a recent partial contribution from anomalous x-ray scattering and from x-ray absorption. A detailed analysis of the corresponding structures indicates that the dispersion correction reduces the Ge-Te bond length, increases the fraction of tetrahedral germanium, and reduces the presence of heteropolar so-called fourfold ABAB rings. Given that these structural features have been stressed to be central for the understanding of the phase-change mechanism, the present results challenge our current understanding of the crystal to amorphous transformation at play. DOI: