原子电负性和极化度对卤代甲烷C 1s电子电离能的影响

以原子的电负性χP和极化度α为基本参数, 估算卤代甲烷CHnY4−n−mZm(Y, Z=F, Cl, Br, I) C 1s电子电离能的电荷效应和松弛效应. 电荷效应由C—H和C—Y(Z)键两端原子的电负性差来度量, 松弛效应由碳原子带的电荷乘上氢和卤素原子极化度来衡量, 进而用电荷效应和松弛效应一起表达卤代甲烷中C 1s电子电离能的静电-松弛屏蔽效应ΔSi. 将ΔSi代入类-Slater模型, 得到卤代甲烷中C 1s电子电离能E1,C的估算方程, 该方程的相关系数r=0.99987, 对27个卤代甲烷的计算值与实验值之间的平均绝对误差仅为0.038 eV, 小于实验误差0.1 eV. 同时, 用留一法(leave-one-out)进行交叉验证(相关系数rcv=0.99977, 预测值与实验值之间的绝对平均误差只有0.049 eV), 结果表明所得方程具有良好的预测能力和稳定性.

Effect of Electronegativity and Polarizability on the C1s Core Ionization Energies of Halomethanes

The charge and relaxation effects on the C 1s core ionization energies of halomethanes CHnY4−n−mZ (Y, Z=F, Cl, Br, I) were evaluated based on the atomic electronegativity χP and the polarizability α. The charge effect was scaled using the electronegativity discrepancy between C and H or the halogen atom in the C-H or C-Y(Z) bond. The relaxation effect (induced dipole) was scaled using the charge on the carbon atom together with the polarizabiliy of the H and halogen atoms. Furthermore, the electrostatic-relaxation shielding ΔSi of the C 1s electron in the halomethane was expressed by the charge effect in combination with the relaxation effect. By introducing the ΔSi into the Slater model, a Slater-like model was obtained for calculating the C 1s core ionization energy E1,C of halomethane, whose correlation coefficient r was 0.99987, and the average absolute error was only 0.038 eV between the calculated and the experimental C 1s core ionization energies for 27 halomethanes. Moreover, the cross-correlation was tested using the leave-one-out (LOO) cross-validation method, and the obtained model had good predictive ability and stability (the correlation coefficient rcv was 0.99977, the average absolute error between the predicted and the experimental values was only 0.049 eV). The proposed model probably laid a good foundation for computing the core ionization energies of various atoms in more complex molecules.