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angle_cosine_periodic.cpp
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rLAMMPS lammps
angle_cosine_periodic.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: Tod A Pascal (Caltech)
------------------------------------------------------------------------- */
#include "math.h"
#include "stdlib.h"
#include "angle_cosine_periodic.h"
#include "atom.h"
#include "neighbor.h"
#include "domain.h"
#include "comm.h"
#include "force.h"
#include "math_const.h"
#include "memory.h"
#include "error.h"
using
namespace
LAMMPS_NS
;
using
namespace
MathConst
;
#define SMALL 0.001
/* ---------------------------------------------------------------------- */
AngleCosinePeriodic
::
AngleCosinePeriodic
(
LAMMPS
*
lmp
)
:
Angle
(
lmp
)
{}
/* ---------------------------------------------------------------------- */
AngleCosinePeriodic
::~
AngleCosinePeriodic
()
{
if
(
allocated
)
{
memory
->
destroy
(
setflag
);
memory
->
destroy
(
k
);
memory
->
destroy
(
b
);
memory
->
destroy
(
multiplicity
);
}
}
/* ---------------------------------------------------------------------- */
void
AngleCosinePeriodic
::
compute
(
int
eflag
,
int
vflag
)
{
int
i
,
i1
,
i2
,
i3
,
n
,
m
,
type
,
b_factor
;
double
delx1
,
dely1
,
delz1
,
delx2
,
dely2
,
delz2
;
double
eangle
,
f1
[
3
],
f3
[
3
];
double
rsq1
,
rsq2
,
r1
,
r2
,
c
,
s
,
a
,
a11
,
a12
,
a22
;
double
tn
,
tn_1
,
tn_2
,
un
,
un_1
,
un_2
;
eangle
=
0.0
;
if
(
eflag
||
vflag
)
ev_setup
(
eflag
,
vflag
);
else
evflag
=
0
;
double
**
x
=
atom
->
x
;
double
**
f
=
atom
->
f
;
int
**
anglelist
=
neighbor
->
anglelist
;
int
nanglelist
=
neighbor
->
nanglelist
;
int
nlocal
=
atom
->
nlocal
;
int
newton_bond
=
force
->
newton_bond
;
for
(
n
=
0
;
n
<
nanglelist
;
n
++
)
{
i1
=
anglelist
[
n
][
0
];
i2
=
anglelist
[
n
][
1
];
i3
=
anglelist
[
n
][
2
];
type
=
anglelist
[
n
][
3
];
// 1st bond
delx1
=
x
[
i1
][
0
]
-
x
[
i2
][
0
];
dely1
=
x
[
i1
][
1
]
-
x
[
i2
][
1
];
delz1
=
x
[
i1
][
2
]
-
x
[
i2
][
2
];
domain
->
minimum_image
(
delx1
,
dely1
,
delz1
);
rsq1
=
delx1
*
delx1
+
dely1
*
dely1
+
delz1
*
delz1
;
r1
=
sqrt
(
rsq1
);
// 2nd bond
delx2
=
x
[
i3
][
0
]
-
x
[
i2
][
0
];
dely2
=
x
[
i3
][
1
]
-
x
[
i2
][
1
];
delz2
=
x
[
i3
][
2
]
-
x
[
i2
][
2
];
domain
->
minimum_image
(
delx2
,
dely2
,
delz2
);
rsq2
=
delx2
*
delx2
+
dely2
*
dely2
+
delz2
*
delz2
;
r2
=
sqrt
(
rsq2
);
// c = cosine of angle
c
=
delx1
*
delx2
+
dely1
*
dely2
+
delz1
*
delz2
;
c
/=
r1
*
r2
;
if
(
c
>
1.0
)
c
=
1.0
;
if
(
c
<
-
1.0
)
c
=
-
1.0
;
m
=
multiplicity
[
type
];
b_factor
=
b
[
type
];
// cos(n*x) = Tn(cos(x))
// Tn(x) = Chebyshev polynomials of the first kind: T_0 = 1, T_1 = x, ...
// recurrence relationship:
// Tn(x) = 2*x*T[n-1](x) - T[n-2](x) where T[-1](x) = 0
// also, dTn(x)/dx = n*U[n-1](x)
// where Un(x) = 2*x*U[n-1](x) - U[n-2](x) and U[-1](x) = 0
// finally need to handle special case for n = 1
tn
=
1.0
;
tn_1
=
1.0
;
tn_2
=
0.0
;
un
=
1.0
;
un_1
=
2.0
;
un_2
=
0.0
;
s
=
sqrt
(
1.0
-
c
*
c
);
if
(
s
<
SMALL
)
s
=
SMALL
;
s
=
1.0
/
s
;
// force & energy
tn_2
=
c
;
for
(
i
=
1
;
i
<=
m
;
i
++
)
{
tn
=
2
*
c
*
tn_1
-
tn_2
;
tn_2
=
tn_1
;
tn_1
=
tn
;
}
for
(
i
=
2
;
i
<=
m
;
i
++
)
{
un
=
2
*
c
*
un_1
-
un_2
;
un_2
=
un_1
;
un_1
=
un
;
}
tn
=
b_factor
*
pow
(
-
1.0
,
m
)
*
tn
;
un
=
b_factor
*
pow
(
-
1.0
,
m
)
*
m
*
un
;
if
(
eflag
)
eangle
=
2
*
k
[
type
]
*
(
1.0
-
tn
);
a
=
-
k
[
type
]
*
un
;
a11
=
a
*
c
/
rsq1
;
a12
=
-
a
/
(
r1
*
r2
);
a22
=
a
*
c
/
rsq2
;
f1
[
0
]
=
a11
*
delx1
+
a12
*
delx2
;
f1
[
1
]
=
a11
*
dely1
+
a12
*
dely2
;
f1
[
2
]
=
a11
*
delz1
+
a12
*
delz2
;
f3
[
0
]
=
a22
*
delx2
+
a12
*
delx1
;
f3
[
1
]
=
a22
*
dely2
+
a12
*
dely1
;
f3
[
2
]
=
a22
*
delz2
+
a12
*
delz1
;
// apply force to each of 3 atoms
if
(
newton_bond
||
i1
<
nlocal
)
{
f
[
i1
][
0
]
+=
f1
[
0
];
f
[
i1
][
1
]
+=
f1
[
1
];
f
[
i1
][
2
]
+=
f1
[
2
];
}
if
(
newton_bond
||
i2
<
nlocal
)
{
f
[
i2
][
0
]
-=
f1
[
0
]
+
f3
[
0
];
f
[
i2
][
1
]
-=
f1
[
1
]
+
f3
[
1
];
f
[
i2
][
2
]
-=
f1
[
2
]
+
f3
[
2
];
}
if
(
newton_bond
||
i3
<
nlocal
)
{
f
[
i3
][
0
]
+=
f3
[
0
];
f
[
i3
][
1
]
+=
f3
[
1
];
f
[
i3
][
2
]
+=
f3
[
2
];
}
if
(
evflag
)
ev_tally
(
i1
,
i2
,
i3
,
nlocal
,
newton_bond
,
eangle
,
f1
,
f3
,
delx1
,
dely1
,
delz1
,
delx2
,
dely2
,
delz2
);
}
}
/* ---------------------------------------------------------------------- */
void
AngleCosinePeriodic
::
allocate
()
{
allocated
=
1
;
int
n
=
atom
->
nangletypes
;
memory
->
create
(
k
,
n
+
1
,
"angle:k"
);
memory
->
create
(
multiplicity
,
n
+
1
,
"angle:multiplicity"
);
memory
->
create
(
b
,
n
+
1
,
"angle:b"
);
memory
->
create
(
setflag
,
n
+
1
,
"angle:setflag"
);
for
(
int
i
=
1
;
i
<=
n
;
i
++
)
setflag
[
i
]
=
0
;
}
/* ----------------------------------------------------------------------
set coeffs for one or more types
------------------------------------------------------------------------- */
void
AngleCosinePeriodic
::
coeff
(
int
narg
,
char
**
arg
)
{
if
(
narg
!=
4
)
error
->
all
(
FLERR
,
"Incorrect args for angle coefficients"
);
if
(
!
allocated
)
allocate
();
int
ilo
,
ihi
;
force
->
bounds
(
arg
[
0
],
atom
->
nangletypes
,
ilo
,
ihi
);
double
c_one
=
atof
(
arg
[
1
]);
int
b_one
=
atoi
(
arg
[
2
]);
int
n_one
=
atoi
(
arg
[
3
]);
if
(
n_one
<=
0
)
error
->
all
(
FLERR
,
"Incorrect args for angle coefficients"
);
int
count
=
0
;
for
(
int
i
=
ilo
;
i
<=
ihi
;
i
++
)
{
k
[
i
]
=
c_one
/
(
n_one
*
n_one
);
b
[
i
]
=
b_one
;
multiplicity
[
i
]
=
n_one
;
setflag
[
i
]
=
1
;
count
++
;
}
if
(
count
==
0
)
error
->
all
(
FLERR
,
"Incorrect args for angle coefficients"
);
}
/* ---------------------------------------------------------------------- */
double
AngleCosinePeriodic
::
equilibrium_angle
(
int
i
)
{
return
MY_PI
;
}
/* ----------------------------------------------------------------------
proc 0 writes out coeffs to restart file
------------------------------------------------------------------------- */
void
AngleCosinePeriodic
::
write_restart
(
FILE
*
fp
)
{
fwrite
(
&
k
[
1
],
sizeof
(
double
),
atom
->
nangletypes
,
fp
);
fwrite
(
&
b
[
1
],
sizeof
(
int
),
atom
->
nangletypes
,
fp
);
fwrite
(
&
multiplicity
[
1
],
sizeof
(
int
),
atom
->
nangletypes
,
fp
);
}
/* ----------------------------------------------------------------------
proc 0 reads coeffs from restart file, bcasts them
------------------------------------------------------------------------- */
void
AngleCosinePeriodic
::
read_restart
(
FILE
*
fp
)
{
allocate
();
if
(
comm
->
me
==
0
)
{
fread
(
&
k
[
1
],
sizeof
(
double
),
atom
->
nangletypes
,
fp
);
fread
(
&
b
[
1
],
sizeof
(
int
),
atom
->
nangletypes
,
fp
);
fread
(
&
multiplicity
[
1
],
sizeof
(
int
),
atom
->
nangletypes
,
fp
);
}
MPI_Bcast
(
&
k
[
1
],
atom
->
nangletypes
,
MPI_DOUBLE
,
0
,
world
);
MPI_Bcast
(
&
b
[
1
],
atom
->
nangletypes
,
MPI_INT
,
0
,
world
);
MPI_Bcast
(
&
multiplicity
[
1
],
atom
->
nangletypes
,
MPI_INT
,
0
,
world
);
for
(
int
i
=
1
;
i
<=
atom
->
nangletypes
;
i
++
)
setflag
[
i
]
=
1
;
}
/* ---------------------------------------------------------------------- */
double
AngleCosinePeriodic
::
single
(
int
type
,
int
i1
,
int
i2
,
int
i3
)
{
double
**
x
=
atom
->
x
;
double
delx1
=
x
[
i1
][
0
]
-
x
[
i2
][
0
];
double
dely1
=
x
[
i1
][
1
]
-
x
[
i2
][
1
];
double
delz1
=
x
[
i1
][
2
]
-
x
[
i2
][
2
];
domain
->
minimum_image
(
delx1
,
dely1
,
delz1
);
double
r1
=
sqrt
(
delx1
*
delx1
+
dely1
*
dely1
+
delz1
*
delz1
);
double
delx2
=
x
[
i3
][
0
]
-
x
[
i2
][
0
];
double
dely2
=
x
[
i3
][
1
]
-
x
[
i2
][
1
];
double
delz2
=
x
[
i3
][
2
]
-
x
[
i2
][
2
];
domain
->
minimum_image
(
delx2
,
dely2
,
delz2
);
double
r2
=
sqrt
(
delx2
*
delx2
+
dely2
*
dely2
+
delz2
*
delz2
);
double
c
=
delx1
*
delx2
+
dely1
*
dely2
+
delz1
*
delz2
;
c
/=
r1
*
r2
;
if
(
c
>
1.0
)
c
=
1.0
;
if
(
c
<
-
1.0
)
c
=
-
1.0
;
c
=
cos
(
acos
(
c
)
*
multiplicity
[
type
]);
return
k
[
type
]
*
(
1.0
-
b
[
type
]
*
pow
(
-
1.0
,
multiplicity
[
type
])
*
c
);
}
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