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应用含有组态作用的ＩＮＤＯ／１量子化学方法，计算了ＬｉＮｂＯ_３和ＫＮｂＯ_３三聚体的基态电子结构及激发态的有关信息，再利用态求和以及性能叠加方法，计算了ＬｉＮｂＯ_３和ＫＮｂＯ_３晶体的线性和非线性光学系数。理论与实验结果进行比较后表明：计算得到的ＬｉＮｂＯ_３晶体的动态光折射率较接近测量值；适用于相匹配的宏观晶体非线性光学系数ｄ（３１），ｄ（３２）相当好地重现了实验测量值。同时，说明了ＫＮｂＯ_３的ｄ（３１），ｄ（３２）大于ＬｉＮｂＯ_３的原因，在于Ｋ离子大的半径和大的电荷离域，加强了ＫＮｂＯ_３晶体对非线性效应的贡献。此外，本文还预计在室温时，从０．７５到１．２５ｅＶ／ｈ和０．８８到１．７８ｅＶ／ｈ频率范围内，ＬｉＮｂＯ_３和ＫＮｂＯ_３各有频率异于１．１７ｅＶ／ｈ的二次非线性光学系数的极大值存在。
The electronic structures and excited states of LiNbO_3 and KNbO_3 trimers were calculated by using INDO / 1 quantum chemistry method. The linearity of LiNbO_3 and KNbO_3 crystals was calculated by sum of states and superposition method. And nonlinear optical coefficient. The comparison of theoretical and experimental results shows that the calculated dynamic refractive index of LiNbO_3 crystal is close to the measured value, and the matched nonlinear optical coefficients d (31) and d (32) of macrocrystal crystal are well reproduced Experimental measurement. The reason why d (31) and d (32) are larger than that of LiNbO_3 for KNbO_3 is also explained. The large radius of K ion and large charge delocalization enhance the contribution of KNbO_3 crystal to the nonlinear effect. In addition, it is also expected that at room temperature, LiNbO_3 and KNbO_3 each have a frequency different from that of 1.17eV / h from 0.75 to 1.25eV / h and 0.88 to 1.78eV / h, respectively The maximum of linear optical coefficients exists.