1 |
mmeineke |
377 |
subroutine v_constrain_a(dt,natoms,mass,rx,ry,rz, & |
2 |
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vx,vy,vz,fx,fy,fz, n_constrained, constraints_sqr, c_i, c_j, & |
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mmeineke |
542 |
box_x, box_y, box_z, isError) |
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mmeineke |
377 |
implicit none |
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6 |
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! ******************************************************************* |
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! ** FIRST PART OF VELOCITY VERLET ALGORITHM ** |
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! ** ** |
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! ** USAGE: ** |
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! ** ** |
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! ** THE FIRST PART OF THE ALGORITHM IS A TAYLOR SERIES WHICH ** |
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! ** ADVANCES POSITIONS FROM T TO T + DT AND VELOCITIES FROM ** |
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! ** T TO T + DT/2. AFTER THIS, THE FORCE ROUTINE IS CALLED. ** |
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! ******************************************************************* |
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! move part a calculate velocities |
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mmeineke |
542 |
INTEGER I, isError |
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mmeineke |
377 |
double precision DT2, DTSQ2 |
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22 |
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double precision box_x, box_y, box_z |
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! Global Parameters |
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INTEGER maxn,ndim,max_dim |
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parameter (maxn=2048,ndim=3,max_dim=3) |
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INTEGER natoms |
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! Global arrays |
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double precision mass(natoms) |
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double precision RX(natoms), RY(natoms), RZ(natoms) !Position |
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double precision VX(natoms), VY(natoms), VZ(natoms) !Velocity |
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double precision FX(natoms), FY(natoms), FZ(natoms) !force |
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! Paramaters for force subroutines |
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double precision dt |
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! variables for the constraint methods |
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integer n_constrained |
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integer c_i(n_constrained), c_j(n_constrained) |
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double precision constraints_sqr(n_constrained) |
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logical done |
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logical moving(natoms), moved(natoms) |
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double precision rptol, tol, tol2 |
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double precision pxab, pyab, pzab, pabsq, rabsq, diffsq |
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double precision rxab, ryab, rzab, rpab, gab |
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double precision dx, dy, dz, rma, rmb |
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mmeineke |
505 |
double precision prSqr, rpabSqr; |
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mmeineke |
377 |
integer a, b, it, maxit |
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parameter (rptol = 1.0d-6, tol = 1.0d-6 ) |
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parameter ( maxit = 100 ) |
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double precision px(natoms), py(natoms), pz(natoms) |
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double precision e_convert |
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parameter ( e_convert = 4.184d-4 ) |
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mmeineke |
542 |
isError = 0 |
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mmeineke |
377 |
DT2 = DT / 2.0d0 |
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DTSQ2 = DT * DT2 |
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DO I = 1, natoms |
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px(I) = RX(I) + DT * VX(I) + & |
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(DTSQ2 * FX(I) * e_convert / mass(i)) |
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py(I) = RY(I) + DT * VY(I) + & |
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(DTSQ2 * FY(I) * e_convert / mass(i)) |
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pz(I) = RZ(I) + DT * VZ(I) + & |
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(DTSQ2 * FZ(I) * e_convert / mass(i)) |
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VX(I) = VX(I) + (DT2 * FX(I) * e_convert / mass(i)) |
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VY(I) = VY(I) + (DT2 * FY(I) * e_convert / mass(i)) |
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VZ(I) = VZ(I) + (DT2 * FZ(I) * e_convert / mass(i)) |
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moving(i) = .false. |
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moved(i) = .true. |
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end do |
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it = 0 |
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done = .false. |
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! start iterative loop |
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do while( (.not. done) .and. (it .le. maxit)) |
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done = .true. |
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do i = 1, n_constrained |
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a = c_i(i) |
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b = c_j(i) |
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if( moved(a) .or. moved(b) ) then |
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pxab = px(a) - px(b) |
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pyab = py(a) - py(b) |
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pzab = pz(a) - pz(b) |
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pxab = pxab - box_x * dsign( 1.0d0, pxab ) & |
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* int( dabs( pxab / box_x ) + 0.5d0 ) |
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pyab = pyab - box_y * dsign( 1.0d0, pyab ) & |
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* int( dabs( pyab / box_y ) + 0.5d0 ) |
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pzab = pzab - box_z * dsign( 1.0d0, pzab ) & |
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* int( dabs( pzab / box_z ) + 0.5d0 ) |
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pabsq = pxab * pxab + pyab * pyab + pzab * pzab |
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rabsq = constraints_sqr(i) |
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diffsq = rabsq - pabsq |
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! write ( *,* )diffsq |
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if( dabs(diffsq) .gt. tol ) then |
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rxab = rx(a) - rx(b) |
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ryab = ry(a) - ry(b) |
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rzab = rz(a) - rz(b) |
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rxab = rxab - box_x * dsign( 1.0d0, rxab ) & |
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* int( dabs( rxab / box_x ) + 0.5d0 ) |
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ryab = ryab - box_y * dsign( 1.0d0, ryab ) & |
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* int( dabs( ryab / box_y ) + 0.5d0 ) |
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rzab = rzab - box_z * dsign( 1.0d0, rzab ) & |
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* int( dabs( rzab / box_z ) + 0.5d0 ) |
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rpab = rxab * pxab + ryab * pyab + rzab * pzab |
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132 |
mmeineke |
505 |
rpabSqr = rpab * rpab |
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prSqr = - diffsq |
134 |
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135 |
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if( rpabSqr .lt. ( rabsq * prSqr )) then |
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mmeineke |
377 |
write (*, '('' Constraint Failure '')' ) |
137 |
mmeineke |
505 |
write (*,*) a-1, b-1,rpabSqr, rabsq * prSqr |
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mmeineke |
542 |
isError = 1 |
139 |
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return |
140 |
mmeineke |
377 |
end if |
141 |
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142 |
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rma = 1.0d0 / mass(a) |
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rmb = 1.0d0 / mass(b) |
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gab = diffsq / ( 2.0d0 * ( rma + rmb ) * rpab ) |
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dx = rxab * gab |
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dy = ryab * gab |
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dz = rzab * gab |
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150 |
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px(a) = px(a) + rma * dx |
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py(a) = py(a) + rma * dy |
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pz(a) = pz(a) + rma * dz |
153 |
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px(b) = px(b) - rmb * dx |
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py(b) = py(b) - rmb * dy |
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pz(b) = pz(b) - rmb * dz |
157 |
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158 |
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dx = dx / dt |
159 |
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dy = dy / dt |
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dz = dz / dt |
161 |
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162 |
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vx(a) = vx(a) + rma * dx |
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vy(a) = vy(a) + rma * dy |
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vz(a) = vz(a) + rma * dz |
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166 |
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vx(b) = vx(b) - rmb * dx |
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vy(b) = vy(b) - rmb * dy |
168 |
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vz(b) = vz(b) - rmb * dz |
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170 |
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moving(a) = .true. |
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moving(b) = .true. |
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done = .false. |
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174 |
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endif |
175 |
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endif |
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enddo |
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do i = 1, natoms |
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moved(i) = moving(i) |
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moving(i) = .false. |
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enddo |
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it = it + 1 |
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enddo |
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! end of iterative loop |
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189 |
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if( .not. done) then |
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write (*, '('' too many constraint iterations in move_a '')' ) |
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mmeineke |
542 |
isError = 1 |
192 |
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return |
193 |
mmeineke |
377 |
endif |
194 |
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195 |
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! store new values |
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197 |
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do i = 1, natoms |
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rx(i) = px(i) |
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ry(i) = py(i) |
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rz(i) = pz(i) |
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enddo |
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RETURN |
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end subroutine v_constrain_a |
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Subroutine v_constrain_b(dt,natoms,mass,rx,ry,rz, & |
208 |
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vx,vy,vz,fx,fy,fz,k, n_constrained, constraints_sqr, & |
209 |
mmeineke |
542 |
c_i, c_j, box_x, box_y, box_z, isError) |
210 |
mmeineke |
377 |
implicit none |
211 |
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212 |
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! ******************************************************************* |
213 |
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! ** SECOND PART OF VELOCITY VERLET ALGORITHM ** |
214 |
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! ** ** |
215 |
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! ** USAGE: ** |
216 |
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! ** ** |
217 |
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! ** THE SECOND PART OF THE ALGORITHM ADVANCES VELOCITIES FROM ** |
218 |
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! ** T + DT/2 TO T + DT. THIS ASSUMES THAT FORCES HAVE BEEN ** |
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! ** COMPUTED IN THE FORCE ROUTINE AND STORED IN FX, FY, FZ. ** |
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! ******************************************************************* |
221 |
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222 |
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! declarations |
223 |
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224 |
mmeineke |
542 |
integer i, isError |
225 |
mmeineke |
377 |
double precision accvel2, dt2 |
226 |
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double precision box_x, box_y, box_z |
227 |
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228 |
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! Global Parameters |
229 |
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230 |
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231 |
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INTEGER natoms |
232 |
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233 |
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! Global arrays |
234 |
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235 |
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double precision mass(natoms) |
236 |
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double precision RX(natoms), RY(natoms), RZ(natoms) !position |
237 |
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double precision VX(natoms), VY(natoms), VZ(natoms) !velocity |
238 |
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double precision FX(natoms), FY(natoms), FZ(natoms) !force |
239 |
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240 |
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241 |
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! Declaration for the kinetic energy |
242 |
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243 |
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double precision k |
244 |
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245 |
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! Paramaters for force subroutines |
246 |
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247 |
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double precision dt |
248 |
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249 |
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! constraint parameters and variables |
250 |
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251 |
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double precision tol, rxab, ryab, rzab, gab |
252 |
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253 |
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double precision vxab, vyab, vzab, dx, dy, dz, rma, rmb, rvab |
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integer a, b, it, maxit, n_constrained |
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parameter ( maxit = 100 ) |
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logical done |
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logical moving(natoms), moved(natoms) |
258 |
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integer c_i(n_constrained), c_j(n_constrained) |
259 |
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double precision constraints_sqr(n_constrained) |
260 |
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261 |
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double precision e_convert |
262 |
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parameter ( e_convert = 4.184d-4 ) |
263 |
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264 |
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265 |
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! ******************************************************************* |
266 |
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267 |
mmeineke |
542 |
isError = 0 |
268 |
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269 |
mmeineke |
377 |
tol = 1.0d-6 / dt |
270 |
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dt2 = dt / 2.0d0 |
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accvel2 = 0.0d0 |
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k = 0.0d0 |
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DO i = 1, natoms |
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VX(I) = VX(I) + (DT2 * FX(I) * e_convert / mass(i)) |
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VY(I) = VY(I) + (DT2 * FY(I) * e_convert / mass(i)) |
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VZ(I) = VZ(I) + (DT2 * FZ(I) * e_convert / mass(i)) |
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moving(i) = .false. |
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moved(i) = .true. |
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enddo |
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283 |
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it = 0 |
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done = .false. |
285 |
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286 |
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do while( (.not. done) .and. ( it .le. maxit) ) |
287 |
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done = .true. |
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290 |
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do i=1, n_constrained |
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a = c_i(i) |
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b = c_j(i) |
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295 |
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if( moved(a) .or. moved(b) ) then |
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297 |
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vxab = vx(a) - vx(b) |
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vyab = vy(a) - vy(b) |
299 |
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vzab = vz(a) - vz(b) |
300 |
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301 |
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rxab = rx(a) - rx(b) |
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ryab = ry(a) - ry(b) |
303 |
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rzab = rz(a) - rz(b) |
304 |
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305 |
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rxab = rxab - box_x * dsign( 1.0d0, rxab ) & |
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* int( dabs( rxab / box_x ) + 0.5d0 ) |
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ryab = ryab - box_y * dsign( 1.0d0, ryab ) & |
308 |
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* int( dabs( ryab / box_y ) + 0.5d0 ) |
309 |
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rzab = rzab - box_z * dsign( 1.0d0, rzab ) & |
310 |
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* int( dabs( rzab / box_z ) + 0.5d0 ) |
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312 |
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313 |
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rma = 1.0d0 / mass(a) |
314 |
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rmb = 1.0d0 / mass(b) |
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316 |
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rvab = rxab * vxab + ryab * vyab + rzab * vzab |
317 |
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318 |
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gab = -rvab / ( ( rma + rmb ) * constraints_sqr(i) ) |
319 |
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320 |
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if ( dabs(gab) .gt. tol) then |
321 |
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322 |
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dx = rxab * gab |
323 |
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dy = ryab * gab |
324 |
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dz = rzab * gab |
325 |
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326 |
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vx(a) = vx(a) + rma * dx |
327 |
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vy(a) = vy(a) + rma * dy |
328 |
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vz(a) = vz(a) + rma * dz |
329 |
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330 |
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vx(b) = vx(b) - rmb * dx |
331 |
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vy(b) = vy(b) - rmb * dy |
332 |
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vz(b) = vz(b) - rmb * dz |
333 |
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334 |
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moving(a) = .true. |
335 |
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moving(b) = .true. |
336 |
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done = .false. |
337 |
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338 |
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endif |
339 |
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340 |
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endif |
341 |
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342 |
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enddo |
343 |
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344 |
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do i = 1, natoms |
345 |
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346 |
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moved(i) = moving(i) |
347 |
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moving(i) = .false. |
348 |
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349 |
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enddo |
350 |
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351 |
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it = it + 1 |
352 |
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353 |
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enddo |
354 |
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355 |
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! End of iterative loop |
356 |
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357 |
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if (.not. done) then |
358 |
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359 |
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write(*, '('' Too many constraint iterations in moveb '')') |
360 |
mmeineke |
542 |
isError = 1 |
361 |
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return |
362 |
mmeineke |
377 |
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363 |
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endif |
364 |
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365 |
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do i = 1, natoms |
366 |
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367 |
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accvel2 = VX(I) ** 2 + VY(I) ** 2 + VZ(I) ** 2 |
368 |
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k = k + 0.5d0 * mass(i) * accvel2 / e_convert |
369 |
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370 |
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end do |
371 |
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372 |
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373 |
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end subroutine v_constrain_b |