论文标题
Quasiparticle $ GW $带结构和lialo $ _2 $四面体和八面体协调结构的带状结构和相变
Quasiparticle self-consistent $GW$ band structures and phase transitions of LiAlO$_2$ in tetrahedrally and octahedrally coordinated structures
论文作者
论文摘要
提出了一项针对Lialo $ _2 $的各个阶段的第一原理计算研究。发现$β$和$γ$四面体相的能量非常接近，而$γ$相位具有最低的能量。八面体$α$相位是一个高压相，从$γ$和$β$相位到$α$的过渡压力确定为约1 GPA。电子带结构使用Quasiparticle自一致（QS）$ GW $方法确定。呈现带边缘的有效质量和带隙的性质。发现最低能量$γ$相位的伪导向间隙为7.69 eV。该差距为$γ$，但对应于禁止过渡的偶极子。介电函数的假想部分和吸收系数以长波长极限和随机相位近似计算，每个阶段没有局部场或电子孔相互作用效应，并讨论了它们的各向异性。使用128个原子超级电池对应于Al网站上的SI掺杂，以$γ$ -lialo $ _2 $为$ n $ type dopant，在广义梯度近似值中对应于Al Sublattice上的3.125 \％Si，在Al Sublattice上对应于Al Sublattice上的3.125 \％Si，较小的16个原子单元和QS $ GW的25 \％si。发现SI显着扰动传统带并降低间隙，但找不到明显分离的深层供体缺陷水平。但是，在氢有效质量近似中，供体的结合能仍然相对较深，几个0.1 eV。
A first-principles computational study is presented of various phases of LiAlO$_2$.The $β$ and $γ$ tetrahedral phases are found to be very close in energy with the $γ$ phase having the lowest energy. The octahedral $α$ phase is a high-pressure phase and the transition pressure from the $γ$ and $β$ phases to $α$ is determined to be about 1 GPa. The electronic band structures are determined using the quasiparticle self-consistent (QS) $GW$ method. The effective masses of the band edges and the nature of the band gaps are presented. The lowest energy $γ$ phase is found to have a pseudodirect gap of 7.69 eV. The gap is direct at $Γ$ but corresponds to a dipole forbidden transition. The imaginary part of the dielectric function and the absorption coefficient are calculated in the long-wavelength limit and the random phase approximation, without local field or electron-hole interaction effects for each phase and their anisotropies are discussed. Si doping on the Al site is investigated as a possible $n$-type dopant in $γ$-LiAlO$_2$ using a 128 atom supercell corresponding to 3.125 \% Si on the Al sublattice in the generalized gradient approximation and a smaller 16 atom cell with 25 \% Si in the QS$GW$ approximation. The Si is found to significantly perturb the conduction band and lower the gap but a clearly separated deep donor defect level is not found. However, the donor binding energy is still expected to be relatively deep, of order a few 0.1 eV in the hydrogenic effective mass approximation.
