First-principles investigation of the structural and vibrational properties of vitreous GeSe2
First-principles investigation of the structural and vibrational properties of vitreous GeSe2
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玻璃态 GeSe2 结构和振动特性的第一性原理研究
DOI：
10.1103/physrevb.75.174207
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发表时间：
2007
影响因子：
3.7
通讯作者：
Alfredo Pasquarello
中科院分区：
文献类型：
--
作者：
L. Giacomazzi;C. Massobrio;Alfredo Pasquarello
使用密度泛函方案，我们研究了玻璃态二硒化锗 (v-GeSe2) 的结构和振动特性。通过使用经典和第一原理分子动力学方法，我们生成了一组显示不同程度的化学无序的结构模型。特别是，代表了两种类型的结构概念：一种在很大程度上保留了四面体顺序，另一种再现了液体第一原理分子动力学模拟中发现的第一邻壳的高度无序性。研究的结构特性包括角分布、第一邻壳层中的原子排列以及配对相关函数。在倒易空间中，我们计算了X射线和中子的总结构因子和部分结构因子。与实验的比较给出了两种结构概念的模型总体上良好的一致性。然后，我们通过振动态密度和非弹性中子谱研究振动特性。所考虑的模型产生相似的光谱并且与实验数据一致。我们还通过基于有限电场应用的密度泛函方案获得红外和拉曼光谱。对于这些光谱，模型之间出现显着差异。与实验的比较有利于模型显示出高度的化学有序性。拉曼强度根据基本原子振动进行分析。支持将拉曼伴线分配给共享边四面体中的 Se 运动。
Using a density-functional scheme, we study the structural and vibrational properties of vitreous germanium diselenide (v-GeSe2). Through the use of classical and first-principles molecular-dynamics methods, we generate a set of structural models showing a varying degree of chemical disorder. In particular, two types of structural concepts are represented: one in which the tetrahedral order is preserved to a very large extent, and one which reproduces the high degree of disorder in first-neighbor shells found in first-principles molecular-dynamics simulations of the liquid. The investigated structural properties include the angular distributions, the atomic arrangements in the first-neighbor shells, and the pair-correlation functions. In reciprocal space, we have calculated the x-ray and neutron total structure factors and the partial structure factors. Comparison with experiment gives overall good agreement for the models of either structural conception. We then investigate the vibrational properties via the vibrational density of states and the inelastic neutron spectrum. The considered models yield similar spectra and agree with experimental data. We also obtain infrared and Raman spectra through a density-functional scheme based on the application of finite electric fields. For these spectra, significant differences appear among the models. The comparison with experiment favors a model showing a high degree of chemical order. The Raman intensity is analyzed in terms of the underlying atomic vibrations. The assignment of the Raman companion line to Se motions in edge-sharing tetrahedra is supported.