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Structural properties of glassy Ge_2Se_3 from first-principles molecular dynamics

机译：基于第一性原理的玻璃态Ge_2Se_3的结构性质

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The structural properties of glassy Ge_2Se_3 were studied in the framework of first-principles molecular dynamics by using the Becke-Lee-Yang-Parr scheme for the treatment of the exchange-correlation functional in density functional theory. Our results for the total neutron structure factor and the total pair distribution function are in very good agreement with the experimental results. When compared to the structural description obtained for liquid Ge_2Se_3, glassy Ge_2Se_3 is found to be characterized by a larger percentage of fourfold coordinated Ge atoms and a lower number of miscoordinations. However, Ge-Ge homopolar bonds inevitably occur due to the lack of Se atoms available, at this concentration, to form GeSe_4 tetrahedra. Focusing on the family of glasses Ge_xSe_(1-x), the present results allow a comparison to be carried out in reciprocal and real space among three prototypical glassy structures. The first was obtained at the stoichiometric composition (glassy GeSe_2), the second at a Se-rich composition (glassy GeSe_4) and the third at a Ge-rich composition (glassy Ge_2Se_3). All networks are consistent with the "8 - N" rule, in particular, glassy GeSe_4, which exhibits the highest degree of chemical order. The electronic structure of glassy Ge_2Se_3 has been characterized by using the Wannier localized orbital formalism. The analysis of the Ge environment shows the presence of dangling, ionocovalent Ge-Se, and covalent bonds, the latter related to Ge-Ge connections.
机译：在第一性原理分子动力学的框架下，利用Becke-Lee-Yang-Parr方案在密度泛函理论中处理交换相关泛函，研究了玻璃态Ge_2Se_3的结构性质。我们关于总中子结构因子和总对分布函数的结果与实验结果非常吻合。当与液体Ge_2Se_3获得的结构描述进行比较时，发现玻璃态的Ge_2Se_3的特征是四重配位的Ge原子百分比更高，错配数量更少。然而，由于在该浓度下缺乏可用于形成GeSe_4四面体的Se原子，不可避免地发生Ge-Ge同质键。着眼于玻璃Ge_xSe_（1-x）的族，本结果允许在三个原型玻璃结构之间的倒数空间和实际空间中进行比较。第一种是在化学计量组成（玻璃态的GeSe_2）下获得的，第二种是在富硒的成分（玻璃态的GeSe_4）下获得的，第三种是在富含Ge的成分（玻璃态Ge_2Se_3的条件下）获得的。所有网络都符合“ 8-N”规则，尤其是玻璃态的GeSe_4，它显示出最高的化学有序度。玻璃态Ge_2Se_3的电子结构已通过使用Wannier局部轨道形式主义进行了表征。对Ge环境的分析表明，存在悬挂，离子共价Ge-Se和共价键，后者与Ge-Ge连接有关。

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