[gmx-users] Force filed of N2 (TraPPE)

[Fei Zhang]

Hello all,

I currently ran into a problem with simulating some N2 gas between graphene
sheets using Gromacs 4.5.7. The density of N2 looks like shown below. N2
molecules tends to go near the up graphene sheet.

[image: Inline image 1]

I used the TraPPE forcefield for N2 molecules and I used PME for
electrostatic calculation.

I think there used to be an bug with PME virial while using non-linear
virtual site, but it is fixed in Gromacs 4.5.6.

Can anyone help me with this problem?

PS: itp file of N2

[ moleculetype ]

    N2G       3

[ atoms ]

;     nr    type   resnr residue    atom    cgnr  charge    mass

       1      VN       1    N2G       VN       1  0.964   0

       2      NN       1    N2G       NN       2  -0.482 14.00670

       3      NN       1    N2G       NN       3  -0.482 14.00670

[ constraints ]

2 3 2 0.110

[ virtual_sites2 ]

1 2 3 1 0.5

Regards,

Hugh