AI摘要:Lammps has updated a new command "fix qtpie/reaxff" in its latest version, which may solve some issues with "fix qeq/reaxff" in charge balance. The usage is similar, but requires an "exp.qtpie" file with data from Chen's 2009 thesis.

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昨天晚上无意间发现了一个新命令fix qtpie/reaxfflammps_19Nov2024 版本刚刚更新的。看起来能解决fix qeq/reaxff在电荷平衡时遇到的一些问题?

https://docs.lammps.org/fix_qtpie_reaxff.html

具体结果还没有对比过。使用上就是将

fix rqeq all qeq/reaxff 1 0.0 10.0 1.0e-6 reaxff

改为

fix rqeq all qtpie/reaxff 1 0.0 10.0 1.0e-6 reaxff exp.qtpie

其中exp.qtpie文件中的数据可以由[Chen 2009:Theory and applications of fluctuating-charge models]博士论文 Table 2.2 获得。

ElementSlater exponentGaussian exponentError
H1.06980.54340.01696
Li0.41740.16680.00148
C0.85630.20690.00162
N0.90890.22140.00166
O0.97450.22400.00167
F0.92060.23130.00169
Na0.43640.09590.00085
Si0.77370.10520.00088
P0.82570.10850.00089
S0.86900.11560.00092
Cl0.91540.11370.00091
K0.45240.06020.00125
Br1.02530.07010.00133
Rb0.51620.04200.00121
I1.07260.06860.00127
Cs0.56630.03070.00114

比如对于C、Si、O三种原子,exp.qtpie如下(#是注释):

# An example gfile. Exponents are taken from Table 2.2 of Chen, J. (2009).
# Theory and applications of fluctuating-charge models.
# The units of the exponents are 1 / (Bohr radius)^2 .
1  0.2069  # C
2  0.1052  # Si
3  0.2240  # O

当然,要安装最新的lammps19Nov2024版本。