论文标题
Quasiparticle $ GW $带结构和Ligao的高压阶段过渡$ _2 $和Nagao $ _2
Quasiparticle self-consistent $GW$ band structures and high-pressure phase transitions of LiGaO$_2$ and NaGaO$_2
论文作者
论文摘要
在Orthorhombic $ PNA2_1 $ Tetrahedrally配位的晶体结构中，提出了针对Ligao2和Nagao2的频带结构的准粒子$ GW $计算。进行间隙附近的频段的对称标记，并为$γ$以$γ$的最小值和晶体场分流价带最小值提取有效的质量张量。发现该差距直接为$γ$，在Ligao2中为5.81 eV，而Nagao2中的EV为5.46 eV。估计电子偶联零点归一化，以降低这些间隙约0.2 eV。在独立的粒子长波长极限内计算光学响应函数，并显示由于VBM的晶体场分裂而导致的吸收量的预期各向异性。结果表明，两种材料都是有希望的候选物，是具有wurtzite的四面体粘结晶体结构的超级间隙半导体。从最低的传导带向更高带的直接过渡，与N型掺杂材料和透明传导应用相关，仅启动于3.9 eV，仅允许一个极化，并且对对称性禁止了几个较高的带过渡。还研究了替代晶体结构，例如$ r \ bar {3} m $和带有四扭曲的$ p4/mmm $ spacegroup的岩石类型相位，都进行了阳离子的八面体配位。发现它们具有较高的能量，但每个配方单元的体积较小约20 \％。确定了这些阶段的过渡压力，对于发现与实验研究非常吻合的LIGAO2。 $ r \ bar {3} m $相位也具有相当高但间接略有间接的带隙，而岩石型相位（如果发现在Ligao2中的距离为3.1 eV，则在Nagao2中的差距约为3.1 eV。
Quasi-particle self-consistent $GW$ calculations are presented for the band structures of LiGaO2 and NaGaO2 in the orthorhombic $Pna2_1$ tetrahedrally coordinated crystal structures. Symmetry labeling of the bands near the gap is carried out and effective mass tensors are extracted for the conduction band minimum and crystal field split valence band maxima at $Γ$. The gap is found to be direct at $Γ$ and is 5.81 eV in LiGaO2 and 5.46 eV in NaGaO2. Electron-phonon coupling zero-point normalization is estimated to lower these gaps by about 0.2 eV. Optical response functions are calculated within the independent particle long wavelength limit and show the expected anisotropy of the absorption onsets due to the crystal field splitting of the VBM. The results show that both materials are promising candidates as ultrawide gap semiconductors with wurtzite based tetrahedrally bonded crystal structures. Direct transitions from the lowest conduction band to higher bands, relevant to n-type doped material and transparent conduction applications are found to start only above 3.9 eV and are allowed for only one polarization, and several higher band transitions are forbidden by symmetry. Alternative crystal structures, such as $R\bar{3}m$ and a rocksalt type phase with tetragonally distorted $P4/mmm$ spacegroup, both with octahedral coordination of the cations are also investigated. They are found to have higher energy but about 20 \% smaller volume per formula unit. The transition pressures to these phases are determined and for LiGaO2 found to be in good agreement with experimental studies. The $R\bar{3}m$phase also has a comparably high but slightly indirect band gap while the rocksalt type phase if found to have a considerably smaller gap of about 3.1 eV in LiGaO2 and 1.0 eV in NaGaO2.
