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: calc_LJ_FF.F90,v 1.2 2003-03-10 19:26:45 chuckv Exp $, $Date: 2003-03-10 19:26:45 $, $Name: not supported by cvs2svn $, $Revision: 1.2 $ |
6 |
|
7 |
|
8 |
|
9 |
module lj_ff |
10 |
use simulation |
11 |
use definitions |
12 |
use generic_lists |
13 |
|
14 |
#ifdef IS_MPI |
15 |
use mpiSimulation |
16 |
#endif |
17 |
implicit none |
18 |
PRIVATE |
19 |
|
20 |
!! Logical has lj force field module been initialized? |
21 |
logical, save :: isljFFinit = .false. |
22 |
|
23 |
|
24 |
!! Public methods and data |
25 |
public :: getLjPot |
26 |
public :: init_ljFF |
27 |
|
28 |
type :: lj_mixed_params |
29 |
!! Mass of Particle |
30 |
real ( kind = dp ) :: mass = 0.0_dp |
31 |
!! Lennard-Jones epslon |
32 |
real ( kind = dp ) :: epsilon = 0.0_dp |
33 |
!! Lennard-Jones Sigma |
34 |
real ( kind = dp ) :: sigma = 0.0_dp |
35 |
!! Lennard-Jones Sigma Squared |
36 |
real ( kind = dp ) :: sigma2 = 0.0_dp |
37 |
!! Lennard-Jones Sigma to sixth |
38 |
real ( kind = dp ) :: sigma6 = 0.0_dp |
39 |
end type lj_mixed_params |
40 |
|
41 |
type (lj_mixed_params), dimension(:,:) :: ljMixed |
42 |
|
43 |
contains |
44 |
|
45 |
subroutine init_ljFF(ListHead,status) |
46 |
type (atype),pointer :: ListHead |
47 |
integer :: nTypes |
48 |
integer, intent(out) :: status |
49 |
|
50 |
integer :: myStatus |
51 |
|
52 |
status = 0 |
53 |
call createMixingList(ListHead,myStatus) |
54 |
if (myStatus /= 0) then |
55 |
status = -1 |
56 |
return |
57 |
end if |
58 |
|
59 |
end subroutine init_ljFF |
60 |
|
61 |
subroutine createMixingList(ListHead,status) |
62 |
type (atype), pointer :: ListHead |
63 |
integer :: listSize |
64 |
integer :: status |
65 |
integer :: i |
66 |
integer :: j |
67 |
|
68 |
integer :: i = 0 |
69 |
integer :: j = 0 |
70 |
type (atype), pointer :: tmpPtr_i => null() |
71 |
type (atype), pointer :: tmpPtr_j => null() |
72 |
status = 0 |
73 |
|
74 |
listSize = getListLen(ListHead) |
75 |
if (listSize == 0) then |
76 |
status = -1 |
77 |
return |
78 |
end if |
79 |
|
80 |
|
81 |
if (.not. associated(ljMixed)) then |
82 |
allocate(ljMixed(listSize,listSize)) |
83 |
else |
84 |
status = -1 |
85 |
return |
86 |
end if |
87 |
|
88 |
|
89 |
|
90 |
tmpPtr_i => ListHead |
91 |
tmpPtr_j => tmpPtr_i%next |
92 |
do while (associated(tmpPtr_i)) |
93 |
i = i + 1 |
94 |
! do self mixing rule |
95 |
ljMixed(i,i)%sigma = tmpPtr_i%sigma |
96 |
|
97 |
ljMixed(i,i)%sigma2 = (ljMixed(i,i)%sigma) ** 2 |
98 |
|
99 |
ljMixed(i,i)%sigma6 = (ljMixed(i,i)%sigma) ** 6 |
100 |
ljMixed(i,i)%epsilon = tmpPtr_i%epsilon |
101 |
|
102 |
j = i + 1 |
103 |
do while (associated(tmpPtr_j)) |
104 |
|
105 |
ljMixed(i,j)%sigma = & |
106 |
calcLJMix("sigma",tmpPtr_i%sigma, & |
107 |
tmpPtr_j%sigma) |
108 |
|
109 |
ljMixed(i,j)%sigma2 = & |
110 |
(ljMixed(i,j)%sigma)**2 |
111 |
|
112 |
ljMixed(i,j)%sigma6 = & |
113 |
(ljMixed(i,j)%sigma)**6 |
114 |
|
115 |
ljMixed(i,j)%epsilon = & |
116 |
calcLJMix("epsilon",tmpPtr_i%epsilon, & |
117 |
tmpPtr_j%epsilon) |
118 |
ljMixed(j,i)%sigma = ljMixed(i,j)%sigma |
119 |
ljMixed(j,i)%sigma2 = ljMixed(i,j)%sigma2 |
120 |
ljMixed(j,i)%sigma6 = ljMixed(i,j)%sigma6 |
121 |
ljMixed(j,i)%epsilon = ljMixed(i,j)%epsilon |
122 |
|
123 |
|
124 |
tmpPtr_j => tmpPtr_j%next |
125 |
j = j + 1 |
126 |
end do |
127 |
! advance pointers |
128 |
tmpPtr_i => tmpPtr_i%next |
129 |
if (associated(tmpPtr_i)) then |
130 |
tmpPtr_j => tmpPtr_i%next |
131 |
endif |
132 |
|
133 |
end do |
134 |
|
135 |
end subroutine createMixingList |
136 |
|
137 |
|
138 |
|
139 |
|
140 |
|
141 |
!! Calculates the potential between two lj particles based on two lj_atype pointers, optionally returns second |
142 |
!! derivatives. |
143 |
subroutine getLjForce(r,pot,dudr,atype1,atype2,d2,status) |
144 |
! arguments |
145 |
!! Length of vector between particles |
146 |
real( kind = dp ), intent(in) :: r |
147 |
!! Potential Energy |
148 |
real( kind = dp ), intent(out) :: pot |
149 |
!! Derivatve wrt postion |
150 |
real( kind = dp ), intent(out) :: dudr |
151 |
!! Second Derivative, optional, used mainly for normal mode calculations. |
152 |
real( kind = dp ), intent(out), optional :: d2 |
153 |
|
154 |
type (atype), pointer :: atype1 |
155 |
type (atype), pointer :: atype2 |
156 |
|
157 |
integer, intent(out), optional :: status |
158 |
|
159 |
! local Variables |
160 |
real( kind = dp ) :: sigma |
161 |
real( kind = dp ) :: sigma2 |
162 |
real( kind = dp ) :: sigma6 |
163 |
real( kind = dp ) :: epsilon |
164 |
|
165 |
real( kind = dp ) :: rcut |
166 |
real( kind = dp ) :: rcut2 |
167 |
real( kind = dp ) :: rcut6 |
168 |
real( kind = dp ) :: r2 |
169 |
real( kind = dp ) :: r6 |
170 |
|
171 |
real( kind = dp ) :: t6 |
172 |
real( kind = dp ) :: t12 |
173 |
real( kind = dp ) :: tp6 |
174 |
real( kind = dp ) :: tp12 |
175 |
real( kind = dp ) :: delta |
176 |
|
177 |
logical :: doSec = .false. |
178 |
|
179 |
integer :: errorStat |
180 |
|
181 |
!! Optional Argument Checking |
182 |
! Check to see if we need to do second derivatives |
183 |
|
184 |
if (present(d2)) doSec = .true. |
185 |
if (present(status)) status = 0 |
186 |
|
187 |
! Look up the correct parameters in the mixing matrix |
188 |
sigma = ljMixed(atype1%atype_ident,atype2%atype_ident)%sigma |
189 |
sigma2 = ljMixed(atype1%atype_ident,atype2%atype_ident)%sigma2 |
190 |
sigma6 = ljMixed(atype1%atype_ident,atype2%atype_ident)%sigma6 |
191 |
epsilon = ljMixed(atype1%atype_ident,atype2%atype_ident)%epsilon |
192 |
|
193 |
|
194 |
|
195 |
|
196 |
call getRcut(rcut,rcut2=rcut2,rcut6=rcut6,status=errorStat) |
197 |
|
198 |
r2 = r * r |
199 |
r6 = r2 * r2 * r2 |
200 |
|
201 |
t6 = sigma6/ r6 |
202 |
t12 = t6 * t6 |
203 |
|
204 |
|
205 |
|
206 |
tp6 = sigma6 / rcut6 |
207 |
tp12 = tp6*tp6 |
208 |
|
209 |
delta = -4.0E0_DP*epsilon * (tp12 - tp6) |
210 |
|
211 |
if (r.le.rcut) then |
212 |
pot = 4.0E0_DP * epsilon * (t12 - t6) + delta |
213 |
dudr = 24.0E0_DP * epsilon * (t6 - 2.0E0_DP*t12) / r |
214 |
if(doSec) d2 = 24.0E0_DP * epsilon * (26.0E0_DP*t12 - 7.0E0_DP*t6)/r/r |
215 |
else |
216 |
pot = 0.0E0_DP |
217 |
dudr = 0.0E0_DP |
218 |
if(doSec) d2 = 0.0E0_DP |
219 |
endif |
220 |
|
221 |
return |
222 |
|
223 |
|
224 |
|
225 |
end subroutine getLJForce |
226 |
|
227 |
|
228 |
!! Calculates the mixing for sigma or epslon based on character string for initialzition of mixing array. |
229 |
function calcLJMix(thisParam,param1,param2,status) result(myMixParam) |
230 |
character(len=*) :: thisParam |
231 |
real(kind = dp) :: param1 |
232 |
real(kind = dp) :: param2 |
233 |
real(kind = dp ) :: myMixParam |
234 |
character(len = getStringLen()) :: thisMixingRule |
235 |
integer, optional :: status |
236 |
|
237 |
!! get the mixing rules from the simulation |
238 |
thisMixingRule = returnMixingRules() |
239 |
myMixParam = 0.0_dp |
240 |
|
241 |
if (present(status)) status = 0 |
242 |
select case (thisMixingRule) |
243 |
case ("standard") |
244 |
select case (thisParam) |
245 |
case ("sigma") |
246 |
myMixParam = 0.5_dp * (param1 + param2) |
247 |
case ("epsilon") |
248 |
myMixParam = sqrt(param1 * param2) |
249 |
case default |
250 |
status = -1 |
251 |
end select |
252 |
case("LJglass") |
253 |
case default |
254 |
status = -1 |
255 |
end select |
256 |
end function calcLJMix |
257 |
|
258 |
|
259 |
|
260 |
end module lj_ff |