[gmx-users] Problem about OPLS Fourier dihedraltypes vs Ryckaert-Bellemans

[pqchen at eyou.com]

Dear gmx-users:
  In the official opls-aa force filed,the torsion parameters of the
CT-CT-CT-CT
is V1=1.740kcal/mol,V2=-0.157kcal/mol,V3=0.279kcal/mol.(V0=?kcal/mol)
  And in the gromacs Rychaert-Bellemans,the torsion parameters of the
CT-CT-CT-CT is
C0=2.93076KJ/mol,C1=-1.46538KJ/mol,C2=0.20934KJ/mol,C3=-1.67472KJ/mol,
C4=0KJ/mol,C5=0KJ/mol;
  Form the formula in the Gromacs manual,I find the formula as follow:
  C0=V0+V2+0.5(V1+V3)
  C1=0.5(3*V3-V1)
  C2=-V2
  C3=-2V3
  C4=0
  C5=0
but I can't correctly translated OPLS Fourier dihedraltypes to Gromacs
Ryckaert-Bellemans parameters.
  Can anybody tell me how to correctly translated the Gromacs RB parameters to
the Official force field.(C#->V#)?





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