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Comparing trunk/mdtools/md_code/lj_FF.F90 (file contents):
Revision 222 by chuckv, Thu Jan 2 21:45:45 2003 UTC vs.
Revision 264 by chuckv, Tue Feb 4 20:16:08 2003 UTC

# Line 1 | Line 1
1 + !! Calculates Long Range forces Lennard-Jones interactions.
2 + !! Corresponds to the force field defined in lj_FF.cpp
3 + !! @author Charles F. Vardeman II
4 + !! @author Matthew Meineke
5 + !! @version $Id: lj_FF.F90,v 1.18 2003-02-04 20:16:08 chuckv Exp $, $Date: 2003-02-04 20:16:08 $, $Name: not supported by cvs2svn $, $Revision: 1.18 $
6 +
7 +
8 +
9   module lj_ff
10    use simulation
11 <  use definitions, ONLY : dp, ndim
11 >  use definitions
12 >  use generic_atypes
13 > #ifdef IS_MPI
14 >  use mpiSimulation
15 > #endif
16    implicit none
17 +  PRIVATE
18  
19 + !! Number of lj_atypes in lj_atype_list
20    integer, save :: n_lj_atypes = 0
21  
22 <  type, public :: lj_atype
23 <     private
24 <     sequence
11 <     integer :: atype_ident = 0
12 <     character(len = 15) :: name = "NULL"
13 <     real ( kind = dp )  :: mass = 0.0_dp
14 <     real ( kind = dp )  :: epslon = 0.0_dp
15 <     real ( kind = dp )  :: sigma = 0.0_dp
16 <     type (lj_atype), pointer :: next => null()
17 <  end type lj_atype
22 > !! Global list of lj atypes in simulation
23 >  type (lj_atype), pointer :: ljListHead => null()
24 >  type (lj_atype), pointer :: ljListTail => null()
25  
19  type (lj_atype), pointer :: lj_atype_list => null()
26  
27 + !! LJ mixing array  
28 +  type (lj_atype), dimension(:,:), pointer :: ljMixed => null()
29 +
30 +
31 + !! Neighbor list and commom arrays
32 + !! This should eventally get moved to a neighbor list type
33 +  integer, allocatable, dimension(:) :: point
34 +  integer, allocatable, dimension(:) :: list
35 +  integer, parameter :: listMultiplier = 80
36 +  integer :: nListAllocs = 0
37 +  integer, parameter :: maxListAllocs = 5
38 +
39 +  logical, save :: firstTime = .True.
40 +
41 + !! Atype identity pointer lists
42 + #ifdef IS_MPI
43 + !! Row lj_atype pointer list
44 +  type (lj_identPtrList), dimension(:), pointer :: identPtrListRow => null()
45 + !! Column lj_atype pointer list
46 +  type (lj_identPtrList), dimension(:), pointer :: identPtrListColumn => null()
47 + #else
48 +  type( lj_identPtrList ), dimension(:), pointer :: identPtrList => null()
49 + #endif
50 +
51 +
52 + !! Logical has lj force field module been initialized?
53 +  logical, save :: isljFFinit = .false.
54 +
55 +
56 + !! Public methods and data
57    public :: new_lj_atype
58 +  public :: do_lj_ff
59 +  public :: getLjPot
60 +  public :: init_ljFF
61  
62 +  
63 +
64 +
65   contains
66  
67 <  subroutine new_lj_atype(name,mass,epslon,sigma,status)
68 <    character( len = 15 ) :: name
67 > !! Adds a new lj_atype to the list.
68 >  subroutine new_lj_atype(ident,mass,epsilon,sigma,status)
69      real( kind = dp ), intent(in) :: mass
70 <    real( kind = dp ), intent(in) :: epslon
71 <    real( kind = dp ), intent(in) :: sigam
70 >    real( kind = dp ), intent(in) :: epsilon
71 >    real( kind = dp ), intent(in) :: sigma
72 >    integer, intent(in) :: ident
73      integer, intent(out) :: status
74  
75 <    type (lj_atype), pointer :: this_lj_atype
33 <    type (lj_atype), pointer :: lj_atype_ptr
34 <
75 >    type (lj_atype), pointer :: newLJ_atype
76      integer :: alloc_error
77      integer :: atype_counter = 0
78 <
78 >    integer :: alloc_size
79 >    integer :: err_stat
80      status = 0
81  
82 <    allocate(this_lj_atype,stat=alloc_error)
82 >
83 >
84 > ! allocate a new atype    
85 >    allocate(newLJ_atype,stat=alloc_error)
86      if (alloc_error /= 0 ) then
87         status = -1
88         return
89      end if
90  
91   ! assign our new lj_atype information
92 <    this_lj_atype%name       = name
93 <    this_lj_atype%mass       = mass
94 <    this_lj_atype%epslon     = epslon
95 <    this_lj_atype%sigma      = sigma
92 >    newLJ_atype%mass        = mass
93 >    newLJ_atype%epsilon     = epsilon
94 >    newLJ_atype%sigma       = sigma
95 >    newLJ_atype%sigma2      = sigma * sigma
96 >    newLJ_atype%sigma6      = newLJ_atype%sigma2 * newLJ_atype%sigma2 &
97 >         * newLJ_atype%sigma2
98 > ! assume that this atype will be successfully added
99 >    newLJ_atype%atype_ident = ident
100 >    newLJ_atype%atype_number = n_lj_atypes + 1
101  
102 +    call add_atype(newLJ_atype,ljListHead,ljListTail,err_stat)
103 +    if (err_stat /= 0 ) then
104 +       status = -1
105 +       return
106 +    endif
107  
108 < ! if lj_atype_list is null then we are at the top of the list.
109 <    if (.not. associated(lj_atype_list)) then
110 <       lj_atype_ptr => this_lj_atype
111 <       atype_counter = 1
112 <    else ! we need to find the bottom of the list
113 <       lj_atype_ptr => lj_atype_list%next
114 <       find_end: do
115 <          if (.not. associated(lj_atype_ptr%next)) then
116 <             exit find_end
117 <          end if
118 <          lj_atype_ptr => lj_atype_ptr%next
119 <       end do find_end
108 >    n_lj_atypes = n_lj_atypes + 1
109 >
110 >
111 >  end subroutine new_lj_atype
112 >
113 >
114 >  subroutine init_ljFF(nComponents,ident, status)
115 > !! Number of components in ident array
116 >    integer, intent(inout) :: nComponents
117 > !! Array of identities nComponents long corresponding to
118 > !! ljatype ident.
119 >    integer, dimension(nComponents),intent(inout) :: ident
120 > !!  Result status, success = 0, error = -1
121 >    integer, intent(out) :: Status
122 >
123 >    integer :: alloc_stat
124 >
125 >    integer :: thisStat
126 >    integer :: i
127 >
128 >    integer :: myNode
129 > #ifdef IS_MPI
130 >    integer, allocatable, dimension(:) :: identRow
131 >    integer, allocatable, dimension(:) :: identCol
132 >    integer :: nrow
133 >    integer :: ncol
134 > #endif
135 >    status = 0
136 >  
137 >
138 >    
139 >
140 > !! if were're not in MPI, we just update ljatypePtrList
141 > #ifndef IS_MPI
142 >    call create_IdentPtrlst(ident,ljListHead,identPtrList,thisStat)
143 >    if ( thisStat /= 0 ) then
144 >       status = -1
145 >       return
146 >    endif
147 >
148 > !! Allocate pointer lists
149 >    allocate(point(nComponents),stat=alloc_stat)
150 >    if (alloc_stat /=0) then
151 >       status = -1
152 >       return
153 >    endif
154 >
155 >    allocate(list(nComponents*listMultiplier),stat=alloc_stat)
156 >    if (alloc_stat /=0) then
157 >       status = -1
158 >       return
159 >    endif
160 >    
161 > ! if were're in MPI, we also have to worry about row and col lists    
162 > #else
163 >  
164 > ! We can only set up forces if mpiSimulation has been setup.
165 >    if (.not. isMPISimSet()) then
166 >       write(default_error,*) "MPI is not set"
167 >       status = -1
168 >       return
169 >    endif
170 >    nrow = getNrow(plan_row)
171 >    ncol = getNcol(plan_col)
172 >    mynode = getMyNode()
173 > !! Allocate temperary arrays to hold gather information
174 >    allocate(identRow(nrow),stat=alloc_stat)
175 >    if (alloc_stat /= 0 ) then
176 >       status = -1
177 >       return
178 >    endif
179 >
180 >    allocate(identCol(ncol),stat=alloc_stat)
181 >    if (alloc_stat /= 0 ) then
182 >       status = -1
183 >       return
184 >    endif
185 >
186 > !! Gather idents into row and column idents
187 >
188 >    call gather(ident,identRow,plan_row)
189 >    call gather(ident,identCol,plan_col)
190 >    
191 >  
192 > !! Create row and col pointer lists
193 >  
194 >    call create_IdentPtrlst(identRow,ljListHead,identPtrListRow,thisStat)
195 >    if (thisStat /= 0 ) then
196 >       status = -1
197 >       return
198 >    endif
199 >  
200 >    call create_IdentPtrlst(identCol,ljListHead,identPtrListColumn,thisStat)
201 >    if (thisStat /= 0 ) then
202 >       status = -1
203 >       return
204 >    endif
205 >
206 > !! free temporary ident arrays
207 >    if (allocated(identCol)) then
208 >       deallocate(identCol)
209      end if
210 +    if (allocated(identCol)) then
211 +       deallocate(identRow)
212 +    endif
213 +
214 + !! Allocate neighbor lists for mpi simulations.
215 +    if (.not. allocated(point)) then
216 +       allocate(point(nrow),stat=alloc_stat)
217 +       if (alloc_stat /=0) then
218 +          status = -1
219 +          return
220 +       endif
221 +
222 +       allocate(list(ncol*listMultiplier),stat=alloc_stat)
223 +       if (alloc_stat /=0) then
224 +          status = -1
225 +          return
226 +       endif
227 +    else
228 +       deallocate(list)
229 +       deallocate(point)
230 +       allocate(point(nrow),stat=alloc_stat)
231 +       if (alloc_stat /=0) then
232 +          status = -1
233 +          return
234 +       endif
235 +
236 +       allocate(list(ncol*listMultiplier),stat=alloc_stat)
237 +       if (alloc_stat /=0) then
238 +          status = -1
239 +          return
240 +       endif
241 +    endif
242 +
243 + #endif
244      
245 <    lj_atype_ptr => this_lj_atype
245 >    call createMixingList(thisStat)
246 >    if (thisStat /= 0) then
247 >       status = -1
248 >       return
249 >    endif
250 >    isljFFinit = .true.
251 >
252 >
253 >  end subroutine init_ljFF
254 >
255 >
256 >
257 >
258 >
259 >
260 >  subroutine createMixingList(status)
261 >    integer :: listSize
262 >    integer :: status
263 >    integer :: i
264 >    integer :: j
265 >
266 >    integer :: outerCounter = 0
267 >    integer :: innerCounter = 0
268 >    type (lj_atype), pointer :: tmpPtrOuter => null()
269 >    type (lj_atype), pointer :: tmpPtrInner => null()
270 >    status = 0
271 >
272 >    listSize = getListLen(ljListHead)
273 >    if (listSize == 0) then
274 >       status = -1
275 >       return
276 >    end if
277 >  
278 >
279 >    if (.not. associated(ljMixed)) then
280 >       allocate(ljMixed(listSize,listSize))
281 >    else
282 >       status = -1
283 >       return
284 >    end if
285 >
286      
69  end subroutine new_lj_atype
287  
288 <  subroutine add_lj_atype()
288 >    tmpPtrOuter => ljListHead
289 >    tmpPtrInner => tmpPtrOuter%next
290 >    do while (associated(tmpPtrOuter))
291 >       outerCounter = outerCounter + 1
292 > ! do self mixing rule
293 >       ljMixed(outerCounter,outerCounter)%sigma  = tmpPtrOuter%sigma
294 >                                                                                                  
295 >       ljMixed(outerCounter,outerCounter)%sigma2  = ljMixed(outerCounter,outerCounter)%sigma &
296 >            * ljMixed(outerCounter,outerCounter)%sigma
297 >                                                                                                  
298 >       ljMixed(outerCounter,outerCounter)%sigma6 = ljMixed(outerCounter,outerCounter)%sigma2 &
299 >            * ljMixed(outerCounter,outerCounter)%sigma2 &
300 >            * ljMixed(outerCounter,outerCounter)%sigma2
301 >                                                                                                  
302 >       ljMixed(outerCounter,outerCounter)%epsilon = tmpPtrOuter%epsilon
303  
304 +       innerCounter = outerCounter + 1
305 +       do while (associated(tmpPtrInner))
306 +          
307 +          ljMixed(outerCounter,innerCounter)%sigma  =  &
308 +               calcLJMix("sigma",tmpPtrOuter%sigma, &
309 +               tmpPtrInner%sigma)
310 +          
311 +          ljMixed(outerCounter,innerCounter)%sigma2  = &
312 +               ljMixed(outerCounter,innerCounter)%sigma &
313 +               * ljMixed(outerCounter,innerCounter)%sigma
314 +          
315 +          ljMixed(outerCounter,innerCounter)%sigma6 = &
316 +               ljMixed(outerCounter,innerCounter)%sigma2 &
317 +               * ljMixed(outerCounter,innerCounter)%sigma2 &
318 +               * ljMixed(outerCounter,innerCounter)%sigma2
319 +          
320 +          ljMixed(outerCounter,innerCounter)%epsilon = &
321 +               calcLJMix("epsilon",tmpPtrOuter%epsilon, &
322 +               tmpPtrInner%epsilon)
323 +          ljMixed(innerCounter,outerCounter)%sigma = ljMixed(outerCounter,innerCounter)%sigma
324 +          ljMixed(innerCounter,outerCounter)%sigma2 = ljMixed(outerCounter,innerCounter)%sigma2
325 +          ljMixed(innerCounter,outerCounter)%sigma6 = ljMixed(outerCounter,innerCounter)%sigma6
326 +          ljMixed(innerCounter,outerCounter)%epsilon = ljMixed(outerCounter,innerCounter)%epsilon
327  
328  
329 <  end subroutine add_lj_atype
329 >          tmpPtrInner => tmpPtrInner%next
330 >          innerCounter = innerCounter + 1
331 >       end do
332 > ! advance pointers
333 >       tmpPtrOuter => tmpPtrOuter%next
334 >       if (associated(tmpPtrOuter)) then
335 >          tmpPtrInner => tmpPtrOuter%next
336 >       endif
337 >      
338 >    end do
339  
340 +  end subroutine createMixingList
341  
342 <  subroutine do_lj_ff(q,f,potE)
343 <    real ( kind = dp ), dimension(ndim,) :: q
344 <    real ( kind = dp ), dimension(ndim,nLRparticles) :: f
342 >
343 >
344 >
345 >
346 >
347 >
348 >
349 > !! FORCE routine Calculates Lennard Jones forces.
350 > !------------------------------------------------------------->
351 >  subroutine do_lj_ff(q,f,potE,do_pot)
352 > !! Position array provided by C, dimensioned by getNlocal
353 >    real ( kind = dp ), dimension(3,getNlocal()) :: q
354 > !! Force array provided by C, dimensioned by getNlocal
355 >    real ( kind = dp ), dimension(3,getNlocal()) :: f
356      real ( kind = dp ) :: potE
357 +    logical ( kind = 2) :: do_pot
358 +    
359 +    type(lj_atype), pointer :: ljAtype_i
360 +    type(lj_atype), pointer :: ljAtype_j
361  
362 + #ifdef IS_MPI
363 +  real( kind = DP ), dimension(3,getNcol(plan_col)) :: efr
364 +  real( kind = DP ) :: pot_local
365 + #else
366 +  real( kind = DP ), dimension(3,getNlocal()) :: efr
367 + #endif
368 +  
369 + !! Local arrays needed for MPI
370 + #ifdef IS_MPI
371 +  real(kind = dp), dimension(3,getNrow(plan_row)) :: qRow
372 +  real(kind = dp), dimension(3,getNcol(plan_col)) :: qCol
373  
374 +  real(kind = dp), dimension(3,getNrow(plan_row)) :: fRow
375 +  real(kind = dp), dimension(3,getNcol(plan_col)) :: fCol
376 +  real(kind = dp), dimension(3,getNlocal()) :: fMPITemp
377  
378 +  real(kind = dp), dimension(getNrow(plan_row)) :: eRow
379 +  real(kind = dp), dimension(getNcol(plan_col)) :: eCol
380  
381 +  real(kind = dp), dimension(getNlocal()) :: eTemp
382 + #endif
383  
384  
385  
386 +  real( kind = DP )   :: pe
387 +  logical             :: update_nlist
388 +
389 +
390 +  integer ::  i, j, jbeg, jend, jnab, idim, jdim, idim2, jdim2, dim, dim2
391 +  integer :: nlist
392 +  integer :: j_start
393 +  integer :: tag_i,tag_j
394 +  real( kind = DP ) ::  r, pot, ftmp, dudr, d2, drdx1, kt1, kt2, kt3, ktmp
395 +  real( kind = DP ) ::  rxi, ryi, rzi, rxij, ryij, rzij, rijsq
396 +  real( kind = DP ) ::  rlistsq, rcutsq,rlist,rcut
397 +
398 + ! a rig that need to be fixed.
399 + #ifdef IS_MPI
400 +  logical :: newtons_thrd = .true.
401 +  real( kind = dp ) :: pe_local
402 +  integer :: nlocal
403 + #endif
404 +  integer :: nrow
405 +  integer :: ncol
406 +  integer :: natoms
407 +
408 +
409 +
410 +
411 + ! Make sure we are properly initialized.
412 +  if (.not. isljFFInit) then
413 +     write(default_error,*) "ERROR: lj_FF has not been properly initialized"
414 +     return
415 +  endif
416 + #ifdef IS_MPI
417 +    if (.not. isMPISimSet()) then
418 +     write(default_error,*) "ERROR: mpiSimulation has not been properly initialized"
419 +     return
420 +  endif
421 + #endif
422 +
423 + !! initialize local variables  
424 +  natoms = getNlocal()
425 +  call getRcut(rcut,rcut2=rcutsq)
426 +  call getRlist(rlist,rlistsq)
427 +
428 + #ifndef IS_MPI
429 +  nrow = natoms - 1
430 +  ncol = natoms
431 + #else
432 +  nrow = getNrow(plan_row)
433 +  ncol = getNcol(plan_col)
434 +  nlocal = natoms
435 +  j_start = 1
436 + #endif
437 +
438 +  
439 + !! See if we need to update neighbor lists
440 +  call check(q,update_nlist)
441 +  if (firstTime) then
442 +     update_nlist = .true.
443 +     firstTime = .false.
444 +  endif
445 +
446 + !--------------WARNING...........................
447 + ! Zero variables, NOTE:::: Forces are zeroed in C
448 + ! Zeroing them here could delete previously computed
449 + ! Forces.
450 + !------------------------------------------------
451 + #ifndef IS_MPI
452 + !  nloops = nloops + 1
453 +  pe = 0.0E0_DP
454 +
455 + #else
456 +    fRow = 0.0E0_DP
457 +    fCol = 0.0E0_DP
458 +
459 +    pe_local = 0.0E0_DP
460 +
461 +    eRow = 0.0E0_DP
462 +    eCol = 0.0E0_DP
463 +    eTemp = 0.0E0_DP
464 + #endif
465 +    efr = 0.0E0_DP
466 +
467 + ! communicate MPI positions
468 + #ifdef IS_MPI    
469 +    call gather(q,qRow,plan_row3d)
470 +    call gather(q,qCol,plan_col3d)
471 + #endif
472 +
473 +
474 +  if (update_nlist) then
475 +
476 +     ! save current configuration, contruct neighbor list,
477 +     ! and calculate forces
478 +     call save_nlist(q)
479 +    
480 +     nlist = 0
481 +    
482 +    
483 +
484 +     do i = 1, nrow
485 +        point(i) = nlist + 1
486 + #ifdef IS_MPI
487 +        ljAtype_i => identPtrListRow(i)%this
488 +        tag_i = tagRow(i)
489 +        rxi = qRow(1,i)
490 +        ryi = qRow(2,i)
491 +        rzi = qRow(3,i)
492 + #else
493 +        ljAtype_i   => identPtrList(i)%this
494 +        j_start = i + 1
495 +        rxi = q(1,i)
496 +        ryi = q(2,i)
497 +        rzi = q(3,i)
498 + #endif
499 +
500 +        inner: do j = j_start, ncol
501 + #ifdef IS_MPI
502 + ! Assign identity pointers and tags
503 +           ljAtype_j => identPtrListColumn(j)%this
504 +           tag_j = tagColumn(j)
505 +           if (newtons_thrd) then
506 +              if (tag_i <= tag_j) then
507 +                 if (mod(tag_i + tag_j,2) == 0) cycle inner
508 +              else                
509 +                 if (mod(tag_i + tag_j,2) == 1) cycle inner
510 +              endif
511 +           endif
512 +
513 +           rxij = wrap(rxi - qCol(1,j), 1)
514 +           ryij = wrap(ryi - qCol(2,j), 2)
515 +           rzij = wrap(rzi - qCol(3,j), 3)
516 + #else          
517 +           ljAtype_j   => identPtrList(j)%this
518 +           rxij = wrap(rxi - q(1,j), 1)
519 +           ryij = wrap(ryi - q(2,j), 2)
520 +           rzij = wrap(rzi - q(3,j), 3)
521 +      
522 + #endif          
523 +           rijsq = rxij*rxij + ryij*ryij + rzij*rzij
524 +
525 + #ifdef IS_MPI
526 +             if (rijsq <=  rlistsq .AND. &
527 +                  tag_j /= tag_i) then
528 + #else
529 +          
530 +             if (rijsq <  rlistsq) then
531 + #endif
532 +            
533 +              nlist = nlist + 1
534 +              if (nlist > size(list)) then
535 + !!  "Change how nlist size is done"
536 +                 write(DEFAULT_ERROR,*) "ERROR: nlist > list size"
537 +              endif
538 +              list(nlist) = j
539 +
540 +    
541 +              if (rijsq <  rcutsq) then
542 +                
543 +                 r = dsqrt(rijsq)
544 +      
545 +                 call getLJPot(r,pot,dudr,ljAtype_i,ljAtype_j)
546 +      
547 + #ifdef IS_MPI
548 +                eRow(i) = eRow(i) + pot*0.5
549 +                eCol(i) = eCol(i) + pot*0.5
550 + #else
551 +                    pe = pe + pot
552 + #endif                
553 +            
554 +                 efr(1,j) = -rxij
555 +                 efr(2,j) = -ryij
556 +                 efr(3,j) = -rzij
557 +
558 +                 do dim = 1, 3  
559 +
560 +            
561 +                    drdx1 = efr(dim,j) / r
562 +                    ftmp = dudr * drdx1
563 +
564 +
565 + #ifdef IS_MPI
566 +                    fCol(dim,j) = fCol(dim,j) - ftmp
567 +                    fRow(dim,i) = fRow(dim,i) + ftmp
568 + #else                    
569 +            
570 +                    f(dim,j) = f(dim,j) - ftmp
571 +                    f(dim,i) = f(dim,i) + ftmp
572 +
573 + #endif                    
574 +                 enddo
575 +              endif
576 +           endif
577 +        enddo inner
578 +     enddo
579 +
580 + #ifdef IS_MPI
581 +     point(nrow + 1) = nlist + 1
582 + #else
583 +     point(natoms) = nlist + 1
584 + #endif
585 +
586 +  else
587 +
588 +     ! use the list to find the neighbors
589 +     do i = 1, nrow
590 +        JBEG = POINT(i)
591 +        JEND = POINT(i+1) - 1
592 +        ! check thiat molecule i has neighbors
593 +        if (jbeg .le. jend) then
594 + #ifdef IS_MPI
595 +           ljAtype_i => identPtrListRow(i)%this
596 +           rxi = qRow(1,i)
597 +           ryi = qRow(2,i)
598 +           rzi = qRow(3,i)
599 + #else
600 +           ljAtype_i   => identPtrList(i)%this
601 +           rxi = q(1,i)
602 +           ryi = q(2,i)
603 +           rzi = q(3,i)
604 + #endif
605 +           do jnab = jbeg, jend
606 +              j = list(jnab)
607 + #ifdef IS_MPI
608 +              ljAtype_j = identPtrListColumn(j)%this
609 +              rxij = wrap(rxi - qCol(1,j), 1)
610 +              ryij = wrap(ryi - qCol(2,j), 2)
611 +              rzij = wrap(rzi - qCol(3,j), 3)
612 + #else
613 +              ljAtype_j = identPtrList(j)%this
614 +              rxij = wrap(rxi - q(1,j), 1)
615 +              ryij = wrap(ryi - q(2,j), 2)
616 +              rzij = wrap(rzi - q(3,j), 3)
617 + #endif
618 +              rijsq = rxij*rxij + ryij*ryij + rzij*rzij
619 +              
620 +              if (rijsq <  rcutsq) then
621 +
622 +                 r = dsqrt(rijsq)
623 +                
624 +                 call getLJPot(r,pot,dudr,ljAtype_i,ljAtype_j)
625 + #ifdef IS_MPI
626 +                eRow(i) = eRow(i) + pot*0.5
627 +                eCol(i) = eCol(i) + pot*0.5
628 + #else
629 +                pe = pe + pot
630 + #endif                
631 +
632 +                
633 +                 efr(1,j) = -rxij
634 +                 efr(2,j) = -ryij
635 +                 efr(3,j) = -rzij
636 +
637 +                 do dim = 1, 3                        
638 +                    
639 +                    drdx1 = efr(dim,j) / r
640 +                    ftmp = dudr * drdx1
641 + #ifdef IS_MPI
642 +                    fCol(dim,j) = fCol(dim,j) - ftmp
643 +                    fRow(dim,i) = fRow(dim,i) + ftmp
644 + #else                    
645 +                    f(dim,j) = f(dim,j) - ftmp
646 +                    f(dim,i) = f(dim,i) + ftmp
647 + #endif                    
648 +                 enddo
649 +              endif
650 +           enddo
651 +        endif
652 +     enddo
653 +  endif
654 +
655 +
656 +
657 + #ifdef IS_MPI
658 +    !!distribute forces
659 +
660 +    call scatter(fRow,f,plan_row3d)
661 +
662 +    call scatter(fCol,fMPITemp,plan_col3d)
663 +
664 +    do i = 1,nlocal
665 +       f(1:3,i) = f(1:3,i) + fMPITemp(1:3,i)
666 +    end do
667 +
668 +
669 +    
670 +    if (do_pot) then
671 +    
672 + ! scatter/gather pot_row into the members of my column
673 +       call scatter(eRow,eTemp,plan_row)
674 +      
675 +       ! scatter/gather pot_local into all other procs
676 +       ! add resultant to get total pot
677 +       do i = 1, nlocal
678 +          pe_local = pe_local + eTemp(i)
679 +       enddo
680 +       if (newtons_thrd) then
681 +          eTemp = 0.0E0_DP
682 +          call scatter(eCol,eTemp,plan_col)
683 +          do i = 1, nlocal
684 +             pe_local = pe_local + eTemp(i)
685 +          enddo
686 +       endif
687 +    
688 +       pe = pe_local
689 +    endif
690 + #endif
691 +
692 +    potE = pe
693 +
694    end subroutine do_lj_ff
695  
696 + !! Calculates the potential between two lj particles based on two lj_atype pointers, optionally returns second
697 + !! derivatives.
698 +  subroutine getLjPot(r,pot,dudr,atype1,atype2,d2,status)
699 + ! arguments
700 + !! Length of vector between particles
701 +    real( kind = dp ), intent(in)  :: r
702 + !! Potential Energy
703 +    real( kind = dp ), intent(out) :: pot
704 + !! Derivatve wrt postion
705 +    real( kind = dp ), intent(out) :: dudr
706 + !! Second Derivative, optional, used mainly for normal mode calculations.
707 +    real( kind = dp ), intent(out), optional :: d2
708 +    
709 +    type (lj_atype), pointer :: atype1
710 +    type (lj_atype), pointer :: atype2
711  
712 +    integer, intent(out), optional :: status
713  
714 + ! local Variables
715 +    real( kind = dp ) :: sigma
716 +    real( kind = dp ) :: sigma2
717 +    real( kind = dp ) :: sigma6
718 +    real( kind = dp ) :: epsilon
719 +
720 +    real( kind = dp ) :: rcut
721 +    real( kind = dp ) :: rcut2
722 +    real( kind = dp ) :: rcut6
723 +    real( kind = dp ) :: r2
724 +    real( kind = dp ) :: r6
725 +
726 +    real( kind = dp ) :: t6
727 +    real( kind = dp ) :: t12
728 +    real( kind = dp ) :: tp6
729 +    real( kind = dp ) :: tp12
730 +    real( kind = dp ) :: delta
731 +
732 +    logical :: doSec = .false.
733 +
734 +    integer :: errorStat
735 +
736 + !! Optional Argument Checking
737 + ! Check to see if we need to do second derivatives
738 +    
739 +    if (present(d2))     doSec = .true.
740 +    if (present(status)) status = 0
741 +
742 + ! Look up the correct parameters in the mixing matrix
743 +    sigma    = ljMixed(atype1%atype_ident,atype2%atype_ident)%sigma
744 +    sigma2   = ljMixed(atype1%atype_ident,atype2%atype_ident)%sigma2
745 +    sigma6   = ljMixed(atype1%atype_ident,atype2%atype_ident)%sigma6
746 +    epsilon  = ljMixed(atype1%atype_ident,atype2%atype_ident)%epsilon
747 +
748 +
749 +    
750 +
751 +    call getRcut(rcut,rcut2=rcut2,rcut6=rcut6,status=errorStat)
752 +    
753 +    r2 = r * r
754 +    r6 = r2 * r2 * r2
755 +
756 +    t6  = sigma6/ r6
757 +    t12 = t6 * t6
758 +
759 +
760 +                                                                              
761 +    tp6 = sigma6 / rcut6
762 +    tp12 = tp6*tp6
763 +                                                                              
764 +    delta = -4.0E0_DP*epsilon * (tp12 - tp6)
765 +                                                                              
766 +    if (r.le.rcut) then
767 +       pot = 4.0E0_DP * epsilon * (t12 - t6) + delta
768 +       dudr = 24.0E0_DP * epsilon * (t6 - 2.0E0_DP*t12) / r
769 +       if(doSec)  d2 = 24.0E0_DP * epsilon * (26.0E0_DP*t12 - 7.0E0_DP*t6)/r/r
770 +    else
771 +       pot = 0.0E0_DP
772 +       dudr = 0.0E0_DP
773 +       if(doSec) d2 = 0.0E0_DP
774 +    endif
775 +                                                                              
776 +  return
777 +
778 +
779 +
780 +  end subroutine getLjPot
781 +
782 +
783 + !! Calculates the mixing for sigma or epslon based on character string for initialzition of mixing array.
784 +  function calcLJMix(thisParam,param1,param2,status) result(myMixParam)
785 +    character(len=*) :: thisParam
786 +    real(kind = dp)  :: param1
787 +    real(kind = dp)  :: param2
788 +    real(kind = dp ) :: myMixParam
789 +    integer, optional :: status
790 +
791 +
792 +    myMixParam = 0.0_dp
793 +
794 +    if (present(status)) status = 0
795 +
796 +    select case (thisParam)
797 +
798 +    case ("sigma")
799 +       myMixParam = 0.5_dp * (param1 + param2)
800 +    case ("epsilon")
801 +       myMixParam = sqrt(param1 * param2)
802 +    case default
803 +       status = -1
804 +    end select
805 +
806 +  end function calcLJMix
807 +
808 +
809 +
810   end module lj_ff

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