标题: 关于CHELPG拟合静电势的输入问题 [打印本页] 作者Author: cahndengbin 时间: 2017-3-26 19:45 标题: 关于CHELPG拟合静电势的输入问题 背景：
我是MD模拟的，最近在利用OPLS_AA的力场参数来模拟碳酸二甲酯DMC，乙烯碳酸酯EC，丙烯碳酸酯PC等几种纯溶剂的物理性质，例如密度、扩散系数、粘度等。
调研文献，发现对于这几个体系研究者大都不直接采用OPLS_AA的原子电荷参数，而倾向选择通过量化的方法拟合气态分子的静电势来获取原子电荷。
如Joural of Molecular Structure:THEOCHEM 806 (2007) 23-34，Structural and thermodynamic properties of liquid ethylene carbonate and propylene carbonate by Monte Carlo Simulations。
我根据文献中的描述也利用Gasuuisan计算EC和PC的原子电荷，但是得到的结果相差较多，所以感到很困惑，烦请大家看看原因何在。
文献中的方法描述：
For consistency with the experimental data, the gas phase geometries of the EC and PC monomers were optimized constraining the ring to a planar conformation. The partial atomic charge distributions which were needed to describe the electrostatic potential in the simulations were computed using the CHELPG procedure. In order to evaluate the effect of electron correlation on charge distributions, the EPS partial charges were computed from both HF and MP2 densities.All the ab initio calculations were carried out with the GAUSSIAN-94 program。
0 1
O -0.01810000 1.11950000 -0.11210000
O -0.01830000 -1.11960000 0.11150000
O 1.98220000 -0.00010000 0.00040000
C -1.37108565 0.69073802 -0.07023094
C -1.37121561 -0.69094780 0.06774637
C 0.76030000 -0.00010000 -0.00030000
H -2.00030509 1.31867081 -0.70647784
H -1.72438657 0.75714750 0.96412714
H -2.00110056 -1.31806968 0.70418316
H -1.72348115 -0.75860724 -0.96693418
D 3 6 1 4 F
D 3 6 2 5 F
最后两行是为了固定O=C-OS-C2和O=C-OS-C1在同一平面上，以保证环状在平面上。
算完的原子电荷如下
47160 points will be used for fitting atomic charges
Fitting point charges to electrostatic potential
Charges from ESP fit, RMS= 0.00278 RRMS= 0.09423:
Charge= 0.00000 Dipole= 6.0666 0.0000 0.0003 Tot= 6.0666
1
1 O -0.496906
2 O -0.496848
3 O -0.641308
4 C 0.240287
5 C 0.240071
6 C 1.061391
7 H 0.023430
8 H 0.023186
9 H 0.023458
10 H 0.023240
但在文献中的结果却是
1 O -0.490
2 O -0.490
3 O -0.610
4 C 0.235
5 C 0.235
6 C 1.000
7 H 0.030
8 H 0.030
9 H 0.030
10 H 0.030
请教各位，可能的原因是什么？谢谢！