HeNO分子光谱常数和非谐振力场的从头算研究

Theoretical study of spectroscopic constants and anharmonic force field of HeNO

本文利用Gaussian 03软件,采用密度泛函理论(B3LYP)以及二阶微扰理论(MP2)的方法结合Dunning相关一致基组cc-pVNZ(N=T,D,Q)以及6-311G、6-311G**、6-311G(2df,2pd)、6-311G(3df,3pd)基组优化了HeNO分子的几何结构,然后在此基础上计算了它们的光谱常数和非谐振力场.通过计算得到了分子的平衡几何结构、基频、转动常数、四次和六次离心畸变常数等,并与相关的实验值和理论值进行了比较;预测了部分光谱常数,其中包括谐振频率、非谐性常数、振转相互作用常数、三次力常数、四次力常数和科里奥利耦合常数.结果表明,在MP2方法下计算的结果要优于B3LYP计算的结果;基组6-311G、6-311G**、6-311G(2df,2pd)、6-311G(3df,3pd)下的结果普遍优于cc-PVNZ(N=T,D,Q)得到的结果.结果还表明,MP2理论方法结合基组6-311G、6-311G**、6-311G(2df,2pd)、6-311G(3df,3pd)基组计算的结果非常接近实验值,对实验测量某些光谱数据有较好的预测作用.

In this thesis, uing the Gaussian 03 software, we adopted density functional theory （B3LYP,） and second order perturbation theory （MP2） methods combining with the relevant consistent basis set cc-pVNZ （N = T, D, Q） and basis sets 6-311G, 6-311G^＊＊ , 6-311G （2d f, 2pd）, 6-311G （3d f, 3pd） to optimize the geometry structure of the molecules HeNO, and then calculated their the spectroscopic constants and the anharmonic force filed based on the method adopted. Through the calculation we got the molecular＇s balance geometry structure, a basis frequency, the turning constants, four-order and six-order centrifugal distortion constant etc. and we compared them with the related experimental value and theoretical values, forecasting the part of the spectroscopic constants, including harminic fre- quences, anharminic constants, vibration-rotation interaction constants, third-order and forth-order force constants and Coriolis coupling constants. The results showed that, by MP2 method the calcula- tion result was superior to those by B3LYP methods; under the basis set of 6-311G, 6-311G^＊＊ , 6-311G （2d f, 2pd）, 6-311G （3d f, 3pd）, the calculation results were widely superior to those under cc-PVNZ （N T, D, Q）. The calculation results showed that the MP2 theory method with the basis sets 6-311G, 6-311G^＊＊ , 6-311G （2d f, 2pd）, 6-311G （3d f, 3pd） led to a calculation result very close to the experimental value, producing a preferable prediction effect of the experimental measuring some spec- trum data.