Dear all,
I was comparing Gromos 45a3 and 53a6 force fields and I found something which I cannot understand. The atom type OA is described in ffG45a3nb.itp as:
;name at.num mass charge ptype c6 c12
OA 8 0.000 0.000 A 0.0022619536 1.505529e-06
and in ffG53a6nb.itp:
OA 8 0.000 0.000 A 0.0022619536 1.505529e-06
which are same parameters.
However, according to Gromos developers the atom type OA has been changed between Gromos 45a3 and 53a6. The parameters given by Gromos developers for 45a3 are
# IAC TYPE SQRT(C6) SQRT(C12(1)) SQRT(C12(2)) SQRT(C12(3))
3 OA 0.04756 1.1250E-3 1.227E-3 0.0
and for 53a6
3 OA 0.04756 1.100E-3 1.227E-3 0.0
The actual numbers are different for parameters used in Gromacs since the way to write parameters is different.
My problem is that there is difference in OA type between 45a3 and 53a6 in parameters given by Gromos developers but not in the files distributed in Gromacs package. Can someone explain this?
BR,
Samuli Ollila
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