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mmeineke |
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subroutine dipole_rf( atom1, atom2, rrfsq, r2, pot, rxij, ryij, rzij, rrf, & |
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dielect, rt, natoms, ulx, uly, ulz, mu, flx, fly, flz, tlx, tly, tlz, & |
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rflx, rfly, rflz, prerf ) |
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!passed arguments |
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integer :: atom1, atom2 ! atom i and j |
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integer :: natoms ! the number of atoms in the system |
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double precision rrfsq ! the square of the reaction field radius |
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double precision r2 ! the square of the distance twixt i and j |
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double precision pot ! hash, reefer, aka. the potential energy |
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double precision rxij, ryij, rzij ! the rij vector components |
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double precision rrf ! the reaction field radius |
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double precision dielect ! the dielectric constant of the reaction field |
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double precision rt ! the radius of the reaction field taper |
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double precision prerf ! dipole equation prefactor |
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!passed arrays |
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double precision, dimension(natoms) :: ulx, uly, ulz ! lab frame unit vector |
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double precision, dimension(natoms) :: mu ! the dipole moments |
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double precision, dimension(natoms) :: flx, fly, flz ! forces |
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double precision, dimension(natoms) :: tlx, tly, tlz ! torques |
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double precision, dimension(natoms) :: rflx, rfly, rflz ! reaction field |
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!local variables |
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double precision dx, dy, dz ! the rji components |
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double precision rij ! the distance twixt i and j |
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double precision dfact1, dfact2, dip2, pre ! assorted prefactors |
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double precision r3, r5 ! the cube and 5th of rij |
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double precision dudx, dudy, dudz ! derivative of u wrt x, y, and z |
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double precision dudu1x, dudu1y, dudu1z ! derivative of u wrt u of atom i |
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double precision dudu2x, dudu2y, dudu2z ! derivative of u wrt u oj atom j |
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double precision rdotu1, rdotu2 ! r dot u of i and j |
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double precision u1dotu2 ! u of i dot u of j |
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double precision taper, dtdr ! taper variables |
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double precision vterm ! dipole potential term |
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double precision taper_2, dtdr_2 |
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logical mine |
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dx = rxij |
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dy = ryij |
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dz = rzij |
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mine = .true. |
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! pre converts from mu in units of debye to kcal/mol |
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pre = 14.38362d0 |
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rij = dsqrt( r2 ) |
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if ( rij .le. rrf ) then |
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! cubic taper |
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if ( rij .lt. rt ) then |
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taper = 1.0d0 |
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dtdr = 0.0d0 |
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else |
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taper = ( rrf + (2.0d0 * rij) - (3.0d0 * rt) ) * ( rrf - rij )**2 / & |
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( ( rrf - rt )**3 ) |
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dtdr = 6.0d0 * ( (rij * rij) - (rij * rt) - (rij * rrf) + & |
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(rrf * rt) ) / ( (rrf - rt)**3 ) |
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endif |
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r3 = r2 * rij |
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r5 = r3 * r2 |
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rdotu1 = (dx * ulx(atom1)) + (dy * uly(atom1)) + (dz * ulz(atom1)) |
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rdotu2 = (dx * ulx(atom2)) + (dy * uly(atom2)) + (dz * ulz(atom2)) |
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u1dotu2 = (ulx(atom1) * ulx(atom2)) + (uly(atom1) * uly(atom2)) + & |
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(ulz(atom1) * ulz(atom2)) |
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dip2 = pre * mu(atom1) * mu(atom2) |
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dfact1 = 3.0d0 * dip2 / r2 |
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dfact2 = 3.0d0 * dip2 / r5 |
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vterm = dip2 * ( (u1dotu2 / r3) - 3.0d0 * (rdotu1 * rdotu2 / r5) ) |
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pot = pot + vterm * taper |
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dudx = ( -dfact1 * dx * & |
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( (u1dotu2 / r3) - ( 5.0d0 * (rdotu1 * rdotu2) / r5 ) ) - & |
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dfact2 * ( (ulx(atom1) * rdotu2) + (ulx(atom2) * rdotu1) ) )* & |
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taper + & |
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vterm * dtdr * dx / rij |
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dudy = ( -dfact1 * dy * & |
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( (u1dotu2 / r3) - ( 5.0d0 * (rdotu1 * rdotu2) / r5 ) ) - & |
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dfact2 * ( (uly(atom1) * rdotu2) + (uly(atom2) * rdotu1) ) ) * & |
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taper + & |
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vterm * dtdr * dy / rij |
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dudz = ( -dfact1 * dz * & |
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( (u1dotu2 / r3) - ( 5.0d0 * (rdotu1 * rdotu2) / r5 ) ) - & |
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dfact2 * ( (ulz(atom1) * rdotu2) + (ulz(atom2) * rdotu1) ) ) * & |
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taper + & |
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vterm * dtdr * dz / rij |
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dudu1x = ( dip2 * ( (ulx(atom2) / r3) - ( 3.0d0 * dx * rdotu2 / r5 ) ) ) & |
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* taper |
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dudu1y = ( dip2 * ( (uly(atom2) / r3) - ( 3.0d0 * dy * rdotu2 / r5 ) ) ) & |
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* taper |
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dudu1z = ( dip2 * ( (ulz(atom2) / r3) - ( 3.0d0 * dz * rdotu2 / r5 ) ) ) & |
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* taper |
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dudu2x = ( dip2 * ( (ulx(atom1) / r3) - ( 3.0d0 * dx * rdotu1 / r5 ) ) ) & |
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* taper |
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dudu2y = ( dip2 * ( (uly(atom1) / r3) - ( 3.0d0 * dy * rdotu1 / r5 ) ) ) & |
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* taper |
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dudu2z = ( dip2 * ( (ulz(atom1) / r3) - ( 3.0d0 * dz * rdotu1 / r5 ) ) ) & |
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* taper |
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flx(atom1) = flx(atom1) + dudx |
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fly(atom1) = fly(atom1) + dudy |
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flz(atom1) = flz(atom1) + dudz |
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flx(atom2) = flx(atom2) - dudx |
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fly(atom2) = fly(atom2) - dudy |
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flz(atom2) = flz(atom2) - dudz |
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tlx(atom1) = tlx(atom1) - (uly(atom1) * dudu1z) + (ulz(atom1) * dudu1y) |
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tly(atom1) = tly(atom1) - (ulz(atom1) * dudu1x) + (ulx(atom1) * dudu1z) |
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tlz(atom1) = tlz(atom1) - (ulx(atom1) * dudu1y) + (uly(atom1) * dudu1x) |
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tlx(atom2) = tlx(atom2) - (uly(atom2) * dudu2z) + (ulz(atom2) * dudu2y) |
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tly(atom2) = tly(atom2) - (ulz(atom2) * dudu2x) + (ulx(atom2) * dudu2z) |
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tlz(atom2) = tlz(atom2) - (ulx(atom2) * dudu2y) + (uly(atom2) * dudu2x) |
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endif |
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return |
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end subroutine dipole_rf |
