! epilogue: softcore (modified 12-6) LJ terms for V1, equals appearing atoms do im_new = 1,icount j = cache_bckptr(im_new) ! atom# of atom j df = cache_df(im_new) ! electrostatic energy times 1/r^2 for the forces delx = cache_x(im_new) ! delta x,y and z dely = cache_y(im_new) delz = cache_z(im_new) delr2 = cache_r2(im_new) ! this contains r^2, note the difference from ew_directe2 rfour=delr2*delr2 r6=rfour*delr2 ic = ico(iaci+iac(j)) ! locate the index in the vdW parameter array if ( ic < 0 ) then b0 = 1.0 b1 = 0.0 else b0 = sigma6(ic) b1 = foureps(ic) end if if ( nsc(i) == nsc(j) .and. emil_sc .eq. 0) then !both atoms are softcore atoms and have normal 6-12 vdw denom = 1.0d0 / ( r6 * b0 ) denom2 = denom * denom sc_ener(7) = sc_ener(7) + b1 * ( denom2 - denom ) ! Potential goes into the softcore energy array df = df + oneweight * b1 * ( 12.0d0 * denom2 - 6.0d0 * denom ) / delr2 ! scaled up by oneweight else ! use the softcore potential denom = 1.0d0 / ( scalpha * ( 1.0d0 - clambda ) + r6 * b0 ) !b0 is 1/(sigma^6) denom2 = denom * denom denom3 = denom2 * denom evdw = evdw + b1 * ( denom2 - denom ) ! softcore potential is part of van der Waals energy ! -- ti decomp if(decpr .and. idecomp > 0) call decpair(3,i,j,b1*(denom2 - denom)/(nstlim/ntpr)) sc_dvdl = sc_dvdl + b1 * ( 2.0d0 * scalpha * denom3 - scalpha * denom2 ) ! -- ti decomp if(decpr .and. idecomp > 0) call decpair(3,i,j,weight1*b1*(2.0d0*scalpha*denom3 - scalpha*denom2)/(nstlim/ntpr)) df = df + b1 * ( 12.0d0 * rfour * b0 * denom3 - 6.0d0 * rfour * b0 * denom2 ) ! collect lambda-dependent contributions to BAR FEP energy differences if (ifmbar /= 0 .and. do_mbar) then do bar_i = 1, bar_states ! remove the current lambda cont bar_cont(bar_i) = bar_cont(bar_i) - b1 * ( denom2 - denom ) end do do bar_i = 1, bar_states denom = 1.0d0 / ( scalpha * ( 1.0d0 - bar_lambda(bar_i) ) + r6 * b0 ) !b0 is 1/(sigma^6) denom2 = denom * denom bar_cont(bar_i) = bar_cont(bar_i) + b1 * ( denom2 - denom ) end do end if end if dfx = delx*df dfy = dely*df dfz = delz*df #ifndef noVIRIAL vxx = vxx - dfx*delx vxy = vxy - dfx*dely vxz = vxz - dfx*delz vyy = vyy - dfy*dely vyz = vyz - dfy*delz vzz = vzz - dfz*delz #endif dumx = dumx + dfx dumy = dumy + dfy dumz = dumz + dfz force(1,j) = force(1,j) + dfx force(2,j) = force(2,j) + dfy force(3,j) = force(3,j) + dfz end do ! im_new = 1,icount