密度泛函理论计算氘代甲烷振动频率和热力学性质

CALCULATIONS OF VIBRATIONAL SPECTRA AND THERMAL PROPERTIES OF METHANE SERIES BY DENSITY FUNCTIONAL THEORY(DFT)

摘要: 用密度泛函方法B3LYP/ 6 31G 对甲烷和各种氘代甲烷进行几何构型全优化 ,优化的结果与实验值吻合。用上述方法对甲烷和各种氘代甲烷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 ,5种化合物的振动频率计算值与实验值的最大相对偏差为 6 3% ,最小相对偏差为 1 1%。标度后振动频率的计算值与实验值的最大相对偏差为 - 2 9% ,最小相对偏差为 0 1%。分子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。

Abstract: The density functional theory calculations using B3' exchange and Lee Yang Parr's correlation functional (B3LYP) with 6 31G  basis set are carried out to study and optimize equilibrium structure and fundamental vibrational frequencies in the equilibrium for CH 4, CH 3D, CH 2D 2, CHD 3, and CD 4. The relative error ranges from 1.1% to 6.3% between the calculation and the observation values of fundamental vibrational frequencies. After scaled, the relative error ranges from 0.1% to 2.9%. With the increase of deteurium substituted atom numbers in methane, entropy and heat capacity increase while total energy and enthalpy decrease.