同位素取代甲醛分子光谱性质的密度泛函理论研究

Calculations of Vibrational Spectra and Thermal Properties of Formaldehyde Series by Density Functional Theory (DFT)

用密度泛函方法B3LYP/6-31G 对甲醛和氘代甲醛进行几何构型全优化,优化的结果与实验值吻合.用上述方法对甲醛、各种氘代甲醛和氚代甲醛分子进行了分子的振动基频和热力学性质计算.计算结果表明甲醛和氘代甲醛标度后振动频率的计算值与实验值的最大相对偏差为4.1%,最小的相对偏差为0.34%.甲醛分子的等容热容和熵随着氘取代原子数的增加而增加;而总能和焓却随之减小.

The density functional theory calculations using B3' exchange and Lee-Yang-Parr's correlation functional (B3LYP) with 6-31G** basis set were carried out to study and optimize equilibrium structure and fundamental vibrational frequencies in the equilibrium for CH2O and CD2O. After scaled, the relative result error was lower than 4.1% between the calculation and the observation values of fundamental vibrational frequencies. This method was used to period properties of formaldehyde which some hydrogen atoms are replaced by tritium atoms. Following deuterium or tritium atom number rises in formaldehyde, entropy and heat capacity increases, while zero-point vibrational energy and enthalpy reduces.