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rLAMMPS lammps
pair_coul_long.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: Paul Crozier (SNL)
------------------------------------------------------------------------- */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "pair_coul_long.h"
#include "atom.h"
#include "comm.h"
#include "force.h"
#include "kspace.h"
#include "neighbor.h"
#include "neigh_list.h"
#include "update.h"
#include "integrate.h"
#include "respa.h"
#include "memory.h"
#include "error.h"
using
namespace
LAMMPS_NS
;
#define EWALD_F 1.12837917
#define EWALD_P 0.3275911
#define A1 0.254829592
#define A2 -0.284496736
#define A3 1.421413741
#define A4 -1.453152027
#define A5 1.061405429
/* ---------------------------------------------------------------------- */
PairCoulLong
::
PairCoulLong
(
LAMMPS
*
lmp
)
:
Pair
(
lmp
)
{
ewaldflag
=
pppmflag
=
1
;
ftable
=
NULL
;
qdist
=
0.0
;
}
/* ---------------------------------------------------------------------- */
PairCoulLong
::~
PairCoulLong
()
{
if
(
!
copymode
)
{
if
(
allocated
)
{
memory
->
destroy
(
setflag
);
memory
->
destroy
(
cutsq
);
memory
->
destroy
(
scale
);
}
if
(
ftable
)
free_tables
();
}
}
/* ---------------------------------------------------------------------- */
void
PairCoulLong
::
compute
(
int
eflag
,
int
vflag
)
{
int
i
,
j
,
ii
,
jj
,
inum
,
jnum
,
itable
,
itype
,
jtype
;
double
qtmp
,
xtmp
,
ytmp
,
ztmp
,
delx
,
dely
,
delz
,
ecoul
,
fpair
;
double
fraction
,
table
;
double
r
,
r2inv
,
forcecoul
,
factor_coul
;
double
grij
,
expm2
,
prefactor
,
t
,
erfc
;
int
*
ilist
,
*
jlist
,
*
numneigh
,
**
firstneigh
;
double
rsq
;
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
;
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_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
<
cut_coulsq
)
{
r2inv
=
1.0
/
rsq
;
if
(
!
ncoultablebits
||
rsq
<=
tabinnersq
)
{
r
=
sqrt
(
rsq
);
grij
=
g_ewald
*
r
;
expm2
=
exp
(
-
grij
*
grij
);
t
=
1.0
/
(
1.0
+
EWALD_P
*
grij
);
erfc
=
t
*
(
A1
+
t
*
(
A2
+
t
*
(
A3
+
t
*
(
A4
+
t
*
A5
))))
*
expm2
;
prefactor
=
qqrd2e
*
scale
[
itype
][
jtype
]
*
qtmp
*
q
[
j
]
/
r
;
forcecoul
=
prefactor
*
(
erfc
+
EWALD_F
*
grij
*
expm2
);
if
(
factor_coul
<
1.0
)
forcecoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
}
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
=
scale
[
itype
][
jtype
]
*
qtmp
*
q
[
j
]
*
table
;
if
(
factor_coul
<
1.0
)
{
table
=
ctable
[
itable
]
+
fraction
*
dctable
[
itable
];
prefactor
=
scale
[
itype
][
jtype
]
*
qtmp
*
q
[
j
]
*
table
;
forcecoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
}
}
fpair
=
forcecoul
*
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
(
!
ncoultablebits
||
rsq
<=
tabinnersq
)
ecoul
=
prefactor
*
erfc
;
else
{
table
=
etable
[
itable
]
+
fraction
*
detable
[
itable
];
ecoul
=
scale
[
itype
][
jtype
]
*
qtmp
*
q
[
j
]
*
table
;
}
if
(
factor_coul
<
1.0
)
ecoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
}
if
(
evflag
)
ev_tally
(
i
,
j
,
nlocal
,
newton_pair
,
0.0
,
ecoul
,
fpair
,
delx
,
dely
,
delz
);
}
}
}
if
(
vflag_fdotr
)
virial_fdotr_compute
();
}
/* ----------------------------------------------------------------------
allocate all arrays
------------------------------------------------------------------------- */
void
PairCoulLong
::
allocate
()
{
allocated
=
1
;
int
n
=
atom
->
ntypes
;
memory
->
create
(
setflag
,
n
+
1
,
n
+
1
,
"pair:setflag"
);
for
(
int
i
=
1
;
i
<=
n
;
i
++
)
for
(
int
j
=
i
;
j
<=
n
;
j
++
)
setflag
[
i
][
j
]
=
0
;
memory
->
create
(
cutsq
,
n
+
1
,
n
+
1
,
"pair:cutsq"
);
memory
->
create
(
scale
,
n
+
1
,
n
+
1
,
"pair:scale"
);
}
/* ----------------------------------------------------------------------
global settings
------------------------------------------------------------------------- */
void
PairCoulLong
::
settings
(
int
narg
,
char
**
arg
)
{
if
(
narg
!=
1
)
error
->
all
(
FLERR
,
"Illegal pair_style command"
);
cut_coul
=
force
->
numeric
(
FLERR
,
arg
[
0
]);
}
/* ----------------------------------------------------------------------
set coeffs for one or more type pairs
------------------------------------------------------------------------- */
void
PairCoulLong
::
coeff
(
int
narg
,
char
**
arg
)
{
if
(
narg
!=
2
)
error
->
all
(
FLERR
,
"Incorrect args for pair coefficients"
);
if
(
!
allocated
)
allocate
();
int
ilo
,
ihi
,
jlo
,
jhi
;
force
->
bounds
(
arg
[
0
],
atom
->
ntypes
,
ilo
,
ihi
);
force
->
bounds
(
arg
[
1
],
atom
->
ntypes
,
jlo
,
jhi
);
int
count
=
0
;
for
(
int
i
=
ilo
;
i
<=
ihi
;
i
++
)
{
for
(
int
j
=
MAX
(
jlo
,
i
);
j
<=
jhi
;
j
++
)
{
scale
[
i
][
j
]
=
1.0
;
setflag
[
i
][
j
]
=
1
;
count
++
;
}
}
if
(
count
==
0
)
error
->
all
(
FLERR
,
"Incorrect args for pair coefficients"
);
}
/* ----------------------------------------------------------------------
init specific to this pair style
------------------------------------------------------------------------- */
void
PairCoulLong
::
init_style
()
{
if
(
!
atom
->
q_flag
)
error
->
all
(
FLERR
,
"Pair style lj/cut/coul/long requires atom attribute q"
);
neighbor
->
request
(
this
,
instance_me
);
cut_coulsq
=
cut_coul
*
cut_coul
;
// insure use of KSpace long-range solver, set g_ewald
if
(
force
->
kspace
==
NULL
)
error
->
all
(
FLERR
,
"Pair style requires a KSpace style"
);
g_ewald
=
force
->
kspace
->
g_ewald
;
// setup force tables
if
(
ncoultablebits
)
init_tables
(
cut_coul
,
NULL
);
}
/* ----------------------------------------------------------------------
init for one type pair i,j and corresponding j,i
------------------------------------------------------------------------- */
double
PairCoulLong
::
init_one
(
int
i
,
int
j
)
{
scale
[
j
][
i
]
=
scale
[
i
][
j
];
return
cut_coul
+
2.0
*
qdist
;
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void
PairCoulLong
::
write_restart
(
FILE
*
fp
)
{
write_restart_settings
(
fp
);
for
(
int
i
=
1
;
i
<=
atom
->
ntypes
;
i
++
)
for
(
int
j
=
i
;
j
<=
atom
->
ntypes
;
j
++
)
{
fwrite
(
&
setflag
[
i
][
j
],
sizeof
(
int
),
1
,
fp
);
if
(
setflag
[
i
][
j
])
fwrite
(
&
scale
[
i
][
j
],
sizeof
(
double
),
1
,
fp
);
}
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void
PairCoulLong
::
read_restart
(
FILE
*
fp
)
{
read_restart_settings
(
fp
);
allocate
();
int
i
,
j
;
int
me
=
comm
->
me
;
for
(
i
=
1
;
i
<=
atom
->
ntypes
;
i
++
)
for
(
j
=
i
;
j
<=
atom
->
ntypes
;
j
++
)
{
if
(
me
==
0
)
fread
(
&
setflag
[
i
][
j
],
sizeof
(
int
),
1
,
fp
);
MPI_Bcast
(
&
setflag
[
i
][
j
],
1
,
MPI_INT
,
0
,
world
);
if
(
setflag
[
i
][
j
])
{
if
(
me
==
0
)
fread
(
&
scale
[
i
][
j
],
sizeof
(
double
),
1
,
fp
);
MPI_Bcast
(
&
scale
[
i
][
j
],
1
,
MPI_DOUBLE
,
0
,
world
);
}
}
}
/* ----------------------------------------------------------------------
proc 0 writes to restart file
------------------------------------------------------------------------- */
void
PairCoulLong
::
write_restart_settings
(
FILE
*
fp
)
{
fwrite
(
&
cut_coul
,
sizeof
(
double
),
1
,
fp
);
fwrite
(
&
offset_flag
,
sizeof
(
int
),
1
,
fp
);
fwrite
(
&
mix_flag
,
sizeof
(
int
),
1
,
fp
);
fwrite
(
&
ncoultablebits
,
sizeof
(
int
),
1
,
fp
);
fwrite
(
&
tabinner
,
sizeof
(
double
),
1
,
fp
);
}
/* ----------------------------------------------------------------------
proc 0 reads from restart file, bcasts
------------------------------------------------------------------------- */
void
PairCoulLong
::
read_restart_settings
(
FILE
*
fp
)
{
if
(
comm
->
me
==
0
)
{
fread
(
&
cut_coul
,
sizeof
(
double
),
1
,
fp
);
fread
(
&
offset_flag
,
sizeof
(
int
),
1
,
fp
);
fread
(
&
mix_flag
,
sizeof
(
int
),
1
,
fp
);
fread
(
&
ncoultablebits
,
sizeof
(
int
),
1
,
fp
);
fread
(
&
tabinner
,
sizeof
(
double
),
1
,
fp
);
}
MPI_Bcast
(
&
cut_coul
,
1
,
MPI_DOUBLE
,
0
,
world
);
MPI_Bcast
(
&
offset_flag
,
1
,
MPI_INT
,
0
,
world
);
MPI_Bcast
(
&
mix_flag
,
1
,
MPI_INT
,
0
,
world
);
MPI_Bcast
(
&
ncoultablebits
,
1
,
MPI_INT
,
0
,
world
);
MPI_Bcast
(
&
tabinner
,
1
,
MPI_DOUBLE
,
0
,
world
);
}
/* ---------------------------------------------------------------------- */
double
PairCoulLong
::
single
(
int
i
,
int
j
,
int
itype
,
int
jtype
,
double
rsq
,
double
factor_coul
,
double
factor_lj
,
double
&
fforce
)
{
double
r2inv
,
r
,
grij
,
expm2
,
t
,
erfc
,
prefactor
;
double
fraction
,
table
,
forcecoul
,
phicoul
;
int
itable
;
r2inv
=
1.0
/
rsq
;
if
(
!
ncoultablebits
||
rsq
<=
tabinnersq
)
{
r
=
sqrt
(
rsq
);
grij
=
g_ewald
*
r
;
expm2
=
exp
(
-
grij
*
grij
);
t
=
1.0
/
(
1.0
+
EWALD_P
*
grij
);
erfc
=
t
*
(
A1
+
t
*
(
A2
+
t
*
(
A3
+
t
*
(
A4
+
t
*
A5
))))
*
expm2
;
prefactor
=
force
->
qqrd2e
*
atom
->
q
[
i
]
*
atom
->
q
[
j
]
/
r
;
forcecoul
=
prefactor
*
(
erfc
+
EWALD_F
*
grij
*
expm2
);
if
(
factor_coul
<
1.0
)
forcecoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
}
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
=
atom
->
q
[
i
]
*
atom
->
q
[
j
]
*
table
;
if
(
factor_coul
<
1.0
)
{
table
=
ctable
[
itable
]
+
fraction
*
dctable
[
itable
];
prefactor
=
atom
->
q
[
i
]
*
atom
->
q
[
j
]
*
table
;
forcecoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
}
}
fforce
=
forcecoul
*
r2inv
;
if
(
!
ncoultablebits
||
rsq
<=
tabinnersq
)
phicoul
=
prefactor
*
erfc
;
else
{
table
=
etable
[
itable
]
+
fraction
*
detable
[
itable
];
phicoul
=
atom
->
q
[
i
]
*
atom
->
q
[
j
]
*
table
;
}
if
(
factor_coul
<
1.0
)
phicoul
-=
(
1.0
-
factor_coul
)
*
prefactor
;
return
phicoul
;
}
/* ---------------------------------------------------------------------- */
void
*
PairCoulLong
::
extract
(
const
char
*
str
,
int
&
dim
)
{
if
(
strcmp
(
str
,
"cut_coul"
)
==
0
)
{
dim
=
0
;
return
(
void
*
)
&
cut_coul
;
}
if
(
strcmp
(
str
,
"scale"
)
==
0
)
{
dim
=
2
;
return
(
void
*
)
scale
;
}
return
NULL
;
}
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