CNRS, Laboratoire de Chimie Physique, Bât. 349, UMR 8000, Orsay, F-91405, France.
J Chem Phys. 2011 Aug 21;135(7):074301. doi: 10.1063/1.3624563.
Various ab initio methods are used to compute the six dimensional potential energy surfaces (6D-PESs) of the ground states of the H(2)NSi and H(2)SiN radicals. They include standard coupled cluster (RCCSD(T)) techniques and the newly developed explicitly correlated RCCSD(T)-F12 methods. For H(2)NSi, the explicitly correlated techniques are viewed to provide data as accurate as the standard coupled cluster techniques, whereas small differences are noticed for H(2)SiN. These PESs are found to be very flat along the out-of-plane and some in-plane bending coordinates. Then, the analytic representations of these PESs are used to solve the nuclear motions by standard perturbation theory and variational calculations. For both isomers, a set of accurate spectroscopic parameters and the vibrational spectrum up to 4000 cm(-1) are predicted. In particular, the analysis of our results shows the occurrence of anharmonic resonances for H(2)SiN even at low energies.
各种从头算方法被用于计算 H(2)NSi 和 H(2)SiN 自由基基态的六维势能面（6D-PESs）。这些方法包括标准耦合簇（RCCSD(T)）技术和新开发的显式相关 RCCSD(T)-F12 方法。对于 H(2)NSi，显式相关技术被认为提供的数据与标准耦合簇技术一样准确，而对于 H(2)SiN 则注意到了微小的差异。这些 PESs 在离平面和一些面内弯曲坐标上非常平坦。然后，通过标准微扰理论和变分计算，利用这些 PESs 的解析表示来求解核运动。对于两种异构体，都预测了一组准确的光谱参数和振动光谱，最高可达 4000 cm(-1)。特别是，我们的结果分析表明，即使在低能时，H(2)SiN 也会发生非谐共振。
