物理截断与电子局域函数结合法研究非晶态结构中的原子成键  

Bonding nature of the amorphous structure studied by a combination of cutoff and electronic localization function

作　　者：王鑫洋[1] 陈念科 王雪鹏[2] 张斌[1] 陈志红[1] 李贤斌[2] 刘显强[1] 

机构地区：[1]北京工业大学固体微结构与性能研究所,北京市重点实验室,北京100124 [2]吉林大学电子科学与工程学院,长春132000

出　　处：《物理学报》2016年第17期269-275,共7页Acta Physica Sinica

基　　金：国家自然科学基金青年科学基金(批准号:11204008)资助的课题~~

摘　　要：本文将常用的键长物理截断方法与电子局域函数方法相结合,用于分析共价系统的非晶态结构,得到了更合理的原子成键信息,提高了非晶态结构模型分析的可靠性.以相变存储材料GeTe合金为例,通过采用上述方法详细研究了GeTe合金非晶态中原子间成键及结构信息,确定了其合理的成键物理截断长度为3.05?,电子局域函数阈值为0.63.研究结果显示,当电子局域函数的数值由0.58逐渐增大至0.63时,结构中所截断的化学键大部分是强度较弱的非同质键(即Ge—Te键),而强度较强的Ge—Ge键的数量几乎不变.对Ge原子配位数和其键角分布等结构信息的分析表明,Ge原子以3配位和4配位为主,其中3配位的Ge原子主要是以缺陷八面体形式存在,而4配位的Ge原子则主要以四面体的形式存在.此外,在本研究工作中所建立的确定成键物理截断长度及电子局域函数阈值的方法也可以应用于其他具有共价键性质的非晶态材料研究.The analysis of the local structure of covalent glass is one of the major challenges for analyzing the amorphous structure. Usually, people use a cutoff distance to determine the coordinated atoms and relevant structural information,such as coordination number and bond angles. Recently, the electron localization function（ELF） has been used to analyze the local structure of amorphous Ge_2Sb_2Te_5. But how to determine the EFL threshold and cutoff distance has not been reported. Here, according to the ab-initio calculations, we systematically investigate the relationship between the bond number and the ELF threshold, and also the cutoff distance in amorphous GeTe. The reasonable value of the ELF threshold and the cutoff distance are determined according to the inflection point and slope change of the bond number with ELF value respectively. Furthermore, the minimal ELF value distributions of Ge—Ge, Ge—Te and Te—Te bonds are presented. The comparison shows that the majority of removed bonds in structural analysis are weak Ge—Te bonds due to the low localization degree of electron. In contrast, the stronger Ge-Ge bonds are almost unchanged when changing the ELF threshold value from 0.58 to 0.63 because of the high localization degree of electron. The average minimal ELF value of Ge—Te bonds in crystalline GeTe is calculated, and it is close to the ELF threshold that is determined by the inflection point. It is easy to find that the Ge—Te bonds which are removed by increasing the ELF threshold are relatively weak. Therefore, these weaker bonds should be removed in structure analysis, which also means that the ELF threshold determined by the inflection point are reasonable value. Finally, based on the EFL threshold value, the coordination number and bond angle distribution of Ge in amorphous GeTe are obtained. The analysis of the coordination number of the Ge atoms shows that as the ELF threshold increases from 0.58 to 0.63, the 5-fold Ge atoms almost disappear because they are against the（8-N） rule

关 键 词：物理截断 电子局域函数 配位数 键角分布 

分 类 号：O562.1[理学—原子与分子物理]