The linear and nonlinear optical properties of the 3-methyl-4-nitropyridine-1-oxyde (POM) crystal have been evaluated using semiempirical quantum chemistry techniques. The scheme includes (i) the evaluation of the polarizability and first hyperpolarizability of increasingly large one-dimensional, two-dimensional, and three-dimensional clusters of POM, (ii) the use of the time-dependent Hartree-Fock approach to determine the static and dynamic responses in combination with semiempirical Austin model 1 Hamiltonian, (iii) the assessment, for the POM monomer and dimer, of the electron correlation effects using second-order Moller-Plesset perturbation theory with several basis sets containing polarization and diffuse functions, (iv) the assessment of the validity of the multiplicative scheme and its application to get effective polarizability and first hyperpolarizability of the POM unit cell in the crystal, (v) the use of a sum-over-states approach to attribute the first hyperpolarizability to a dominant charge-transfer excited state, and (vi) comparison with experimental data as well as with calculated values obtained using the oriented gas approximation.

中文翻译：

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3-甲基-4-硝基吡啶-1-氧化物（POM）晶体的线性和二阶非线性磁化率的理论研究。

使用半经验量子化学技术已经评估了3-甲基-4-硝基吡啶-1-氧基（POM）晶体的线性和非线性光学性质。该方案包括（i）评估越来越大的POM一维，二维和三维簇的极化率和第一超极化率，（ii）使用时变的Hartree-Fock方法来确定POM。结合半经验奥斯汀模型1哈密顿量的静态和动态响应，（iii）使用二阶Moller-Plesset摄动理论对POM单体和二聚体的电子相关效应进行评估，该理论具有多个包含极化和扩散函数的基本集，