全氟化合物热力学性质的密度泛函理论研究

Density functional theory studies on the thermodynamic properties of perfluorinated compounds

用密度泛函理论B3LYP方法,在6-31G基组水平上,对12个全氟化合物分子进行了全优化计算,得到其分子零点振动能EZPV、热能校正值Eth、恒容热容CVΦ、标准熵SΦ以及配分函数lgQ等热力学参数,并计算了这些分子的电性拓扑状态指数Em.通过最佳变量子集回归建立了电性拓扑状态指数与热力学参数之间的QSPR模型,模型的相关系数R2分别为1.000,1.000,1.000,0.999和1.000,采用逐一剔除法得到的交叉验证相关系数R2cv分别为0.999,1.000,1.000,0.999和1.000,利用建构的数学模型得到热力学性质的相对平均误差分别为0.43%,0.41%,0.46%,0.41%和0.71%.从方程可以看出,F原子取代基数量是影响全氟化合物分子热力学参数大小的主要因素,检验证明所建模型具有良好的稳定性和预测能力.

Using the density functional theory （DFT）, we calculate the quantum chemical parameters of 12 perfluorinated compounds at the B3LYP/6-31G level. We get the thermodynamic property con- sist of zero-point vibration energy Ezev, thermal correction value Eth, heat capacity at constant volume Cvφ, standard entropy S~, partition function lgQ and the electrotopological state indices Era. By the leaps-and-bounds regression analysis, we establish the quantitative structure-property relationships （QSPR） of the thermodynamic property. The correlation coefficients R2 are 1. 000,1. 000,1. 000, 0. 999 and 1. 000,and the leave-one-out （LOO） cross validation R2cv of the model are 0. 999,1. 000, 1. 000,0. 999 and 1. 000 respectively. The relative mean error between the calculated values and the predicted values of Ezpv, Eth,Cvφ, SO and lgQ are 0.43%,0.41%,0.46%,0.41% and 0.71%, re- spectively. The number of F atom substitution is the main factor,which has the greatest impact on the values of the thermodynamics properties. It is proves that QSPR models have good robustness and good prediction capability.