NaNO_2晶体线性和非线性光学系数的计算

使用从头计算平面波赝势方法，计算了NaNO2晶体电子能带结构，并使用改进的倍频公式计算了它的线性折射率和静态二级非线性系数，所得到的结果和实验值相符.采用实空间原子切割方法分析了阳离子和阴离子基团对光学性质的贡献.计算表明(NO2)-基团对双折射率和倍频系数的贡献占主要地位，从而进一步验证了阴离子基团理论的正确性.

CALCULATIONS FOR THE LINEAR AND NONLINEAR OPTICAL COEFFICIENTS OF NaNO_2 CRYSTAL

Based on a plane-wave pseudopotential method,the electronic structure calculations of NaNO2 from first principles are perforined.The linear refractive indices and the static second-harmonic generation (SHG) coefficients are also calculated by the SHG formula improved by us.The calculated values are in good agreement with the experimental values.A real-space atom-cutting method is adopted to analyze the respective contributions of the cation and anionic groups to optical response.The results show that the contribution of the (NO2)- anionic group to the birefringence and the SHG coefficients is dominated in NaNO2 crystal,which is in agreement with the result obtained by the anionic group model.