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pair_buck_coul_long_cs.cpp
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Tue, Sep 3, 03:37
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Thu, Sep 5, 03:37 (2 d)
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rLAMMPS lammps
pair_buck_coul_long_cs.cpp
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/* ----------------------------------------------------------------------
LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
http://lammps.sandia.gov, Sandia National Laboratories
Steve Plimpton, sjplimp@sandia.gov
Copyright (2003) Sandia Corporation. Under the terms of Contract
DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
certain rights in this software. This software is distributed under
the GNU General Public License.
See the README file in the top-level LAMMPS directory.
------------------------------------------------------------------------- */
/* ----------------------------------------------------------------------
Contributing author: Hendrik Heenen (hendrik.heenen@mytum.de)
------------------------------------------------------------------------- */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pair_buck_coul_long_cs.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "kspace.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "math_const.h"
#include "memory.h"
#include "error.h"
using
namespace
LAMMPS_NS
;
using
namespace
MathConst
;
#define EWALD_F 1.12837917
#define EWALD_P 9.95473818e-1
#define B0 -0.1335096380159268
#define B1 -2.57839507e-1
#define B2 -1.37203639e-1
#define B3 -8.88822059e-3
#define B4 -5.80844129e-3
#define B5 1.14652755e-1
#define EPSILON 1.0e-20
#define EPS_EWALD 1.0e-6
#define EPS_EWALD_SQR 1.0e-12
/* ---------------------------------------------------------------------- */
PairBuckCoulLongCS
::
PairBuckCoulLongCS
(
LAMMPS
*
lmp
)
:
PairBuckCoulLong
(
lmp
)
{
ewaldflag
=
pppmflag
=
1
;
writedata
=
1
;
ftable
=
NULL
;
}
/* ---------------------------------------------------------------------- */
void
PairBuckCoulLongCS
::
compute
(
int
eflag
,
int
vflag
)
{
int
i
,
j
,
ii
,
jj
,
inum
,
jnum
,
itable
,
itype
,
jtype
;
double
qtmp
,
xtmp
,
ytmp
,
ztmp
,
delx
,
dely
,
delz
,
evdwl
,
ecoul
,
fpair
;
double
fraction
,
table
;
double
rsq
,
r2inv
,
r6inv
,
forcecoul
,
forcebuck
,
factor_coul
,
factor_lj
;
double
grij
,
expm2
,
prefactor
,
t
,
erfc
,
u
;
double
r
,
rexp
;
int
*
ilist
,
*
jlist
,
*
numneigh
,
**
firstneigh
;
evdwl
=
ecoul
=
0.0
;
if
(
eflag
||
vflag
)
ev_setup
(
eflag
,
vflag
);
else
evflag
=
vflag_fdotr
=
0
;
double
**
x
=
atom
->
x
;
double
**
f
=
atom
->
f
;
double
*
q
=
atom
->
q
;
int
*
type
=
atom
->
type
;
int
nlocal
=
atom
->
nlocal
;
double
*
special_coul
=
force
->
special_coul
;
double
*
special_lj
=
force
->
special_lj
;
int
newton_pair
=
force
->
newton_pair
;
double
qqrd2e
=
force
->
qqrd2e
;
inum
=
list
->
inum
;
ilist
=
list
->
ilist
;
numneigh
=
list
->
numneigh
;
firstneigh
=
list
->
firstneigh
;
// loop over neighbors of my atoms
for
(
ii
=
0
;
ii
<
inum
;
ii
++
)
{
i
=
ilist
[
ii
];
qtmp
=
q
[
i
];
xtmp
=
x
[
i
][
0
];
ytmp
=
x
[
i
][
1
];
ztmp
=
x
[
i
][
2
];
itype
=
type
[
i
];
jlist
=
firstneigh
[
i
];
jnum
=
numneigh
[
i
];
for
(
jj
=
0
;
jj
<
jnum
;
jj
++
)
{
j
=
jlist
[
jj
];
factor_lj
=
special_lj
[
sbmask
(
j
)];
factor_coul
=
special_coul
[
sbmask
(
j
)];
j
&=
NEIGHMASK
;
delx
=
xtmp
-
x
[
j
][
0
];
dely
=
ytmp
-
x
[
j
][
1
];
delz
=
ztmp
-
x
[
j
][
2
];
rsq
=
delx
*
delx
+
dely
*
dely
+
delz
*
delz
;
jtype
=
type
[
j
];
if
(
rsq
<
cutsq
[
itype
][
jtype
])
{
rsq
+=
EPSILON
;
// Add Epsilon for case: r = 0; Interaction must be removed by special bond;
r2inv
=
1.0
/
rsq
;
if
(
rsq
<
cut_coulsq
)
{
if
(
!
ncoultablebits
||
rsq
<=
tabinnersq
)
{
r
=
sqrt
(
rsq
);
prefactor
=
qqrd2e
*
qtmp
*
q
[
j
];
if
(
factor_coul
<
1.0
)
{
// When bonded parts are being calculated a minimal distance (EPS_EWALD)
// has to be added to the prefactor and erfc in order to make the
// used approximation functions for the Ewald correction valid
grij
=
g_ewald
*
(
r
+
EPS_EWALD
);
expm2
=
exp
(
-
grij
*
grij
);
t
=
1.0
/
(
1.0
+
EWALD_P
*
grij
);
u
=
1.0
-
t
;
erfc
=
t
*
(
1.
+
u
*
(
B0
+
u
*
(
B1
+
u
*
(
B2
+
u
*
(
B3
+
u
*
(
B4
+
u
*
B5
))))))
*
expm2
;
prefactor
/=
(
r
+
EPS_EWALD
);
forcecoul
=
prefactor
*
(
erfc
+
EWALD_F
*
grij
*
expm2
-
(
1.0
-
factor_coul
));
// Additionally r2inv needs to be accordingly modified since the later
// scaling of the overall force shall be consistent
r2inv
=
1.0
/
(
rsq
+
EPS_EWALD_SQR
);
}
else
{
grij
=
g_ewald
*
r
;
expm2
=
exp
(
-
grij
*
grij
);
t
=
1.0
/
(
1.0
+
EWALD_P
*
grij
);
u
=
1.0
-
t
;
erfc
=
t
*
(
1.
+
u
*
(
B0
+
u
*
(
B1
+
u
*
(
B2
+
u
*
(
B3
+
u
*
(
B4
+
u
*
B5
))))))
*
expm2
;
prefactor
/=
r
;
forcecoul
=
prefactor
*
(
erfc
+
EWALD_F
*
grij
*
expm2
);
}
}
else
{
union_int_float_t
rsq_lookup
;
rsq_lookup
.
f
=
rsq
;
itable
=
rsq_lookup
.
i
&
ncoulmask
;
itable
>>=
ncoulshiftbits
;
fraction
=
(
rsq_lookup
.
f
-
rtable
[
itable
])
*
drtable
[
itable
];
table
=
ftable
[
itable
]
+
fraction
*
dftable
[
itable
];
forcecoul
=
qtmp
*
q
[
j
]
*
table
;
if
(
factor_coul
<
1.0
)
{
table
=
ctable
[
itable
]
+
fraction
*
dctable
[
itable
];
prefactor
=
qtmp
*
q
[
j
]
*
table
;
forcecoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
}
}
}
else
forcecoul
=
0.0
;
if
(
rsq
<
cut_ljsq
[
itype
][
jtype
])
{
r
=
sqrt
(
rsq
);
r6inv
=
r2inv
*
r2inv
*
r2inv
;
rexp
=
exp
(
-
r
*
rhoinv
[
itype
][
jtype
]);
forcebuck
=
buck1
[
itype
][
jtype
]
*
r
*
rexp
-
buck2
[
itype
][
jtype
]
*
r6inv
;
}
else
forcebuck
=
0.0
;
fpair
=
(
forcecoul
+
factor_lj
*
forcebuck
)
*
r2inv
;
f
[
i
][
0
]
+=
delx
*
fpair
;
f
[
i
][
1
]
+=
dely
*
fpair
;
f
[
i
][
2
]
+=
delz
*
fpair
;
if
(
newton_pair
||
j
<
nlocal
)
{
f
[
j
][
0
]
-=
delx
*
fpair
;
f
[
j
][
1
]
-=
dely
*
fpair
;
f
[
j
][
2
]
-=
delz
*
fpair
;
}
if
(
eflag
)
{
if
(
rsq
<
cut_coulsq
)
{
if
(
!
ncoultablebits
||
rsq
<=
tabinnersq
)
ecoul
=
prefactor
*
erfc
;
else
{
table
=
etable
[
itable
]
+
fraction
*
detable
[
itable
];
ecoul
=
qtmp
*
q
[
j
]
*
table
;
}
if
(
factor_coul
<
1.0
)
ecoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
}
else
ecoul
=
0.0
;
if
(
rsq
<
cut_ljsq
[
itype
][
jtype
])
{
evdwl
=
a
[
itype
][
jtype
]
*
rexp
-
c
[
itype
][
jtype
]
*
r6inv
-
offset
[
itype
][
jtype
];
evdwl
*=
factor_lj
;
}
else
evdwl
=
0.0
;
}
if
(
evflag
)
ev_tally
(
i
,
j
,
nlocal
,
newton_pair
,
evdwl
,
ecoul
,
fpair
,
delx
,
dely
,
delz
);
}
}
}
if
(
vflag_fdotr
)
virial_fdotr_compute
();
}
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