高压下Zn_2GeO_4带隙变化的第一性原理研究  

First-principles study on the band-gap changes of Zn_2GeO_4 under high pressure

作　　者：吴成国[1] 武文远[1] 龚艳春[1] 戴斌飞[1] 何苏红[1] 黄雁华[1] 

机构地区：[1]解放军理工大学理学院,南京211101

出　　处：《物理学报》2015年第11期224-230,共7页Acta Physica Sinica

摘　　要：采用基于密度泛函理论的第一性原理计算研究了Zn2Ge O4晶体在高压下的电子结构和带隙变化行为.研究结果发现,随着压强的增加,Zn2Ge O4能带间隙先变大,在压强为9.7 GPa时达到最大值,然后减小.通过电子态密度、电荷布居数和电子差分密度分布图的研究分析可知:在低压区域(0<P<9.7 GPa),带隙的变大主要是由于原子间距离的减小造成的共价性增强和Ge原子随压强的变大局域性增强引起的;在高压区域(P>9.7 GPa),则是出现了离域现象,诱发了离域电子的产生,从而使带隙减小.In this paper, the properties of electronic structure and band-gap change of Zn2GeO4 under high pressures are investigated using the first principles method based on the density functional theory （DFT）. We demonstrate that the density functional theory calculations performed with the local density approximation （LDA） allows for a significantly better reproduction of lattice constants, the unit cell volume and the band gap of Zn2GeO4 than those performed with the generalized gradient approximation （GGA）, so the electronic structure and the band-gap changes of Zn2GeO4 under high pressures can be systematically investigated by LDA. Result of the state density without application of pressures shows that Zn2GeO4 is a wide direct-band-gap semiconductor, and the top of the valence band is mainly composed of Zn 3d and O 2p states, while the conduction band is dominated by the Zn 4 s and Ge 4p. Calculated results about the energy band structure of Zn2GeO4 show that the band gaps of Zn2GeO4 first increase and have a peak at around 9.7 GPa, and then gradually decrease with increasing pressure. The Mulliken charge populations and the value of net charges of Zn2GeO4 at different pressures reveal that the charge distribution of O atoms does not change obviously, while the s and p orbital charges of Zn and Ge atom distributions have obviously charge transfer above 9.7 GPa, and result in an increase of Zn and Ge atom net charges. Analysis of the state density, the Mulliken charge populations, and the electronic density difference of Zn2GeO4 in （210） plane at different pressures indicate： in the low-pressure region （0〈 P〈 9.7 GPa）, the increase in band gap is mainly due to the covalent enhancement between atomic distances and the Ge atoms larger localization; and in the high-pressure region （P 〉 9.7 GPa）, the delocalization phenomenon becomes dominant due to the fact that the delocalization action exceeds the force between the bonding state and anti-bonding state, which induces the decrease of the

关 键 词：Zn2GeO4 能带间隙 态密度 密度泛函理论 

分 类 号：O469[理学—凝聚态物理]