[gmx-users] Tabulated potentials

[张正财]

Dear all,
        I want to add the Morse potential ( U=D*[exp(a*(1-r/r0)-2*exp(a/2*(1-r/r0)] ) for nonbonded interactions between CH4-CH4. So, I made three table files to correspond to the interactions between H-H, C-H, and C-C, and I changed vdwtype=user ,Dispcorr=no , energrps = C H , and energrps_table = C C C H H H. However, when I used NVT ensemble to calculate the pressure of pure methane system, I didnot get accurate pressure, actually the pressure is about 20 MPa smaller than the experiment value. Could you give me some suggestions about what is wrong with my set or what I missed in adding the table?
Sincerely yours,
Zhengcai,