[gmx-users] non-bonded parameters

[nk yx]

hi all,
    I am confused about the calculation of non-bonded LJ parameters in the 
ffG43a1nb.itp. According to the manual, the combination rule of C6 and C12 
is:
Cij(6)=(Cii(6)*Cjj(6))^0.5
Cij(12)=(Cii(12)*Cjj(12))^0.5
However,in the ffG43a1nb.itp file, the values seem not to be in agreement 
with the rule. For example,
O  C6=0.0022619536 C12=7.4149321e-07
OM C6=0.0022619536 C12=7.4149321e-07
OA C6=0.0022619536 C12=1.505529e-06

According to the rule, 
O OA   C6=0.0022619536 
       C12=(7.4149321e-07 * 1.505529e-06)^0.5 = 1.0565697e-06 
but the value is 1.380375e-06 in the ffG43a1nb.itp.
In addition, C12 value between O and OM, and tween O and OA should be the 
same, but in the file, C12 is 1.38380375e-06 and 2.258907e-06,respectively.
Could anybody tell me why? Thanks in advance.

Regards,
nkyx

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