铌酸锂晶体电子结构和光学性质计算

Calculation for Electronic Structure and Optical Properties of LiNbO_3 Crystals

使用基于从头计算平面波赝势法的CASTEP量化软件计算了铌酸锂(LiNbO3)晶体的电子能带结构和线性光学系数,采用耦合微扰方法(CPHF)计算了铌酸锂晶体的非线性光学系数.折射率和倍频系数的计算结果与实验结果基本符合,计算表明铌酸锂晶体中Nb原子的4d轨道电子态和O原子的2p轨道电子态发生了明显杂化.通过分析铌酸锂晶体的价带顶和导带底电子态密度的组成特点可知这些轨道电子态的杂化是其非线性光学效应的主要来源,同时计算还表明铌酸锂晶体中Li-O键具有明显的共价键性.

The electronic energy band structure and linear optical coefficient of LiNbO3 crystal were calculated by firs-principle calculation pseudo-potential plane wave method in CASTEP package, and the nonlinear optical coefficient of LiNbO3 was calculated based on coupled Hatree-Fock （CPHF） model. The calculated refractive indices and second harmoni-generation （SHG） coefficients matched well with experimental results. The results shows that the 4d orbital of Nb atom and 2p orbital of O atom in LiNbO3 crystal are hybridized, which is the origin of the nonlinear property which can be deduced from the characteristics of electronic density of states on upper part of valence bands and bottom part of conduction bands. The calculated results also indicate that the Li-O bond in the crystal shows typical covalent characteristic.