162 lines
4.4 KiB
C++
162 lines
4.4 KiB
C++
/* ----------------------------------------------------------------------
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LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
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http://lammps.sandia.gov, Sandia National Laboratories
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Steve Plimpton, sjplimp@sandia.gov
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Copyright (2003) Sandia Corporation. Under the terms of Contract
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DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
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certain rights in this software. This software is distributed under
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the GNU General Public License.
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See the README file in the top-level LAMMPS directory.
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------------------------------------------------------------------------- */
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#include <math.h>
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#include <stdio.h>
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#include <string.h>
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#include "fix_nve_line.h"
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#include "atom.h"
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#include "atom_vec_line.h"
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#include "domain.h"
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#include "math_const.h"
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#include "error.h"
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using namespace LAMMPS_NS;
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using namespace FixConst;
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using namespace MathConst;
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#define INERTIA (1.0/12.0) // moment of inertia prefactor for line segment
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/* ---------------------------------------------------------------------- */
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FixNVELine::FixNVELine(LAMMPS *lmp, int narg, char **arg) :
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FixNVE(lmp, narg, arg)
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{
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if (narg != 3) error->all(FLERR,"Illegal fix nve/line command");
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time_integrate = 1;
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MINUSPI = -MY_PI;
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TWOPI = 2.0*MY_PI;
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}
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/* ---------------------------------------------------------------------- */
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int FixNVELine::setmask()
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{
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int mask = 0;
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mask |= INITIAL_INTEGRATE;
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mask |= FINAL_INTEGRATE;
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mask |= INITIAL_INTEGRATE_RESPA;
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mask |= FINAL_INTEGRATE_RESPA;
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return mask;
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}
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/* ---------------------------------------------------------------------- */
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void FixNVELine::init()
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{
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// error checks
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avec = (AtomVecLine *) atom->style_match("line");
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if (!avec) error->all(FLERR,"Fix nve/line requires atom style line");
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if (domain->dimension != 2)
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error->all(FLERR,"Fix nve/line can only be used for 2d simulations");
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// check that all particles are line segments
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// no point particles allowed
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int *line = atom->line;
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int *mask = atom->mask;
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int nlocal = atom->nlocal;
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for (int i = 0; i < nlocal; i++)
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if (mask[i] & groupbit) {
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if (line[i] < 0) error->one(FLERR,"Fix nve/line requires line particles");
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}
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FixNVE::init();
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}
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/* ---------------------------------------------------------------------- */
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void FixNVELine::initial_integrate(int vflag)
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{
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double dtfm,dtirotate,length,theta;
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AtomVecLine::Bonus *bonus = avec->bonus;
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int *line = atom->line;
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double **x = atom->x;
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double **v = atom->v;
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double **f = atom->f;
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double **omega = atom->omega;
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double **torque = atom->torque;
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double *rmass = atom->rmass;
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int *mask = atom->mask;
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int nlocal = atom->nlocal;
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if (igroup == atom->firstgroup) nlocal = atom->nfirst;
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// set timestep here since dt may have changed or come via rRESPA
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double dtfrotate = dtf / INERTIA;
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// update v,x,omega,theta for all particles
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// d_omega/dt = torque / inertia
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// bound theta by -PI to PI
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for (int i = 0; i < nlocal; i++)
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if (mask[i] & groupbit) {
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dtfm = dtf / rmass[i];
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v[i][0] += dtfm * f[i][0];
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v[i][1] += dtfm * f[i][1];
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x[i][0] += dtv * v[i][0];
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x[i][1] += dtv * v[i][1];
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length = bonus[line[i]].length;
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theta = bonus[line[i]].theta;
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dtirotate = dtfrotate / (length*length*rmass[i]);
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omega[i][2] += dtirotate * torque[i][2];
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theta += dtv * omega[i][2];
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while (theta <= MINUSPI) theta += TWOPI;
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while (theta > MY_PI) theta -= TWOPI;
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bonus[line[i]].theta = theta;
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}
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}
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/* ---------------------------------------------------------------------- */
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void FixNVELine::final_integrate()
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{
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double dtfm,dtirotate,length;
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AtomVecLine::Bonus *bonus = avec->bonus;
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int *line = atom->line;
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double **v = atom->v;
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double **f = atom->f;
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double **omega = atom->omega;
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double **torque = atom->torque;
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double *rmass = atom->rmass;
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int *mask = atom->mask;
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int nlocal = atom->nlocal;
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if (igroup == atom->firstgroup) nlocal = atom->nfirst;
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// set timestep here since dt may have changed or come via rRESPA
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double dtfrotate = dtf / INERTIA;
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// update v,omega for all particles
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// d_omega/dt = torque / inertia
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for (int i = 0; i < nlocal; i++)
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if (mask[i] & groupbit) {
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dtfm = dtf / rmass[i];
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v[i][0] += dtfm * f[i][0];
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v[i][1] += dtfm * f[i][1];
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length = bonus[line[i]].length;
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dtirotate = dtfrotate / (length*length*rmass[i]);
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omega[i][2] += dtirotate * torque[i][2];
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}
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}
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