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Added hexatic bond orientational order parameter

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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@14236 f3b2605a-c512-4ea7-a41b-209d697bcdaa
This commit is contained in:
athomps
2015-11-05 06:53:08 +00:00
parent d212245359
commit 3bc7350704
5 changed files with 61 additions and 23 deletions
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37
src/compute_hexorder_atom.cpp
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@ -16,6 +16,7 @@
------------------------------------------------------------------------- */
#include <math.h>
#include <complex>
#include <string.h>
#include <stdlib.h>
#include "compute_hexorder_atom.h"
@ -38,10 +39,24 @@ using namespace LAMMPS_NS;
ComputeHexOrderAtom::ComputeHexOrderAtom(LAMMPS *lmp, int narg, char **arg) :
Compute(lmp, narg, arg)
{
if (narg != 3) error->all(FLERR,"Illegal compute hexorder/atom command");
if (narg < 3 ) error->all(FLERR,"Illegal compute hexorder/atom command");
nnn = 6;
// process optional args
int iarg = 3;
while (iarg < narg) {
if (strcmp(arg[iarg],"degree") == 0) {
if (iarg+1 > narg) error->all(FLERR,"Illegal lattice command");
nnn = force->numeric(FLERR,arg[iarg+1]);
if (nnn < 0)
error->all(FLERR,"Illegal lattice command");
iarg += 2;
}
}
ncol = 2;
peratom_flag = 1;
size_peratom_cols = ncol;
@ -50,7 +65,6 @@ ComputeHexOrderAtom::ComputeHexOrderAtom(LAMMPS *lmp, int narg, char **arg) :
maxneigh = 0;
distsq = NULL;
nearest = NULL;
nnn = 6;
}
/* ---------------------------------------------------------------------- */
@ -187,7 +201,7 @@ void ComputeHexOrderAtom::compute_peratom()
delx = xtmp - x[j][0];
dely = ytmp - x[j][1];
double u, v;
calc_q6(delx, dely, u, v);
calc_qn(delx, dely, u, v);
usum += u;
vsum += v;
}
@ -197,6 +211,8 @@ void ComputeHexOrderAtom::compute_peratom()
}
}
// this might be faster than pow(std::complex) on some platforms
inline void ComputeHexOrderAtom::calc_q6(double delx, double dely, double &u, double &v) {
double rinv = 1.0/sqrt(delx*delx+dely*dely);
double x = delx*rinv;
@ -205,10 +221,23 @@ inline void ComputeHexOrderAtom::calc_q6(double delx, double dely, double &u, do
double b1 = y*y;
double b2 = b1*b1;
double b3 = b2*b1;
// (x + i y)^6 coeffs: 1, 6, -15, -20, 15, 6, -1
u = (( a - 15*b1)*a + 15*b2)*a - b3;
v = ((6*a - 20*b1)*a + 6*b2)*x*y;
}
inline void ComputeHexOrderAtom::calc_qn(double delx, double dely, double &u, double &v) {
double rinv = 1.0/sqrt(delx*delx+dely*dely);
double x = delx*rinv;
double y = dely*rinv;
std::complex<double> z = x + y*1i;
std::complex<double> zn = pow(z,nnn);
u = real(zn);
v = imag(zn);
}
/* ----------------------------------------------------------------------
select2 routine from Numerical Recipes (slightly modified)
find k smallest values in array of length n