arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1405.7783cond-mat.mtrl-sci
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MNH $_2$(M=Li,Na,K,Rb)的电子结构、弹性和光学性质的密度泛函研究

Density functional study of electronic structure, elastic and optical properties of MNH$_2$ (M=Li, Na, K, Rb)

K. Ramesh Babu, G. Vaitheeswaran

摘要:

本文采用第一性原理密度泛函方法对氮基固体贮氢材料LiNH $_2$、NaNH $_2$、KNH $_2$和RbNH $_2$的电子结构、弹性和光学性质进行了系统的研究。用标准密度泛函理论和色散修正的密度泛函理论计算了基态结构性质。我们发现范德华相互作用在LiNH $_2$中占主导地位,而在其他碱金属酰胺中相对较弱。计算的弹性常数表明,所有的化合物是机械稳定的和LiNH $_2$被发现是较硬的碱金属酰胺材料。计算熔融温度,其遵循顺序RbNH $_2$ $<$ KNH $_2$ $<$ NaNH $_2$ $<$ LiNH $_2$。用改进的B-J势计算了化合物的电子能带结构,发现所有化合物都是带隙较大的绝缘体. [NH $_2$ ] $^-$衍生态在整个价带区完全占主导地位,而金属原子态占据导带。利用计算得到的能带结构分析了价带和导带之间不同的带间光跃迁。我们的计算表明,这些材料具有相当大的光学各向异性。

英文摘要:

We report systematic first principles density functional study on the electronic structure, elastic and optical properties of nitrogen based solid hydrogen storage materials LiNH$_2$, NaNH$_2$, KNH$_2$, and RbNH$_2$. The ground state structural properties are calculated by using standard density functional theory and also dispersion corrected density functional theory. We find that van der Waals interactions are dominant in LiNH$_2$ whereas they are relatively weak in other alkali metal amides. The calculated elastic constants show that all the compounds are mechanically stable and LiNH$_2$ is found to be stiffer material among the alkali metal amides. The melting temperatures are calculated and which follows the order RbNH$_2$ $<$ KNH$_2$ $<$ NaNH$_2$ $<$ LiNH$_2$. The electronic band structure is calculated by using the Tran-Blaha modified Becke-Johnson potential and found that all the compounds are insulators with a considerable band gap. The [NH$_2$]$^-$ derived states are completely dominating in the entire valence band region while the metal atom states occupy the conduction band. The calculated band structure is used to analyze the different interband optical transitions occur between valence and conduction bands. Our calculations show that these materials have considerable optical anisotropy.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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