153 lines
4.5 KiB
C++
153 lines
4.5 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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/* ----------------------------------------------------------------------
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Contributing author: Mike Brown (SNL)
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------------------------------------------------------------------------- */
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#include <math.h>
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#include "fix_nh_sphere.h"
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#include "atom.h"
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#include "atom_vec.h"
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#include "group.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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#define INERTIA 0.4 // moment of inertia prefactor for sphere
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/* ---------------------------------------------------------------------- */
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FixNHSphere::FixNHSphere(LAMMPS *lmp, int narg, char **arg) :
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FixNH(lmp, narg, arg)
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{
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if (!atom->sphere_flag)
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error->all(FLERR,"Fix nvt/nph/npt sphere requires atom style sphere");
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}
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/* ---------------------------------------------------------------------- */
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void FixNHSphere::init()
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{
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// check that all particles are finite-size
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// no point particles allowed
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double *radius = atom->radius;
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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 (radius[i] == 0.0)
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error->one(FLERR,"Fix nvt/sphere requires extended particles");
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FixNH::init();
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}
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/* ----------------------------------------------------------------------
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perform half-step update of rotational velocities
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-----------------------------------------------------------------------*/
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void FixNHSphere::nve_v()
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{
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// standard nve_v velocity update
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FixNH::nve_v();
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double **omega = atom->omega;
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double **torque = atom->torque;
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double *radius = atom->radius;
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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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double dtirotate;
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// update omega for all particles
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// d_omega/dt = torque / inertia
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// 4 cases depending on radius vs shape and rmass vs mass
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for (int i = 0; i < nlocal; i++)
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if (mask[i] & groupbit) {
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dtirotate = dtfrotate / (radius[i]*radius[i]*rmass[i]);
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omega[i][0] += dtirotate*torque[i][0];
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omega[i][1] += dtirotate*torque[i][1];
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omega[i][2] += dtirotate*torque[i][2];
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}
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}
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/* ----------------------------------------------------------------------
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perform full-step update of position with dipole orientation, if requested
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-----------------------------------------------------------------------*/
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void FixNHSphere::nve_x()
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{
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// standard nve_x position update
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FixNH::nve_x();
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// update mu for dipoles
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// d_mu/dt = omega cross mu
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// renormalize mu to dipole length
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if (dipole_flag) {
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double msq,scale,g[3];
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double **mu = atom->mu;
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double **omega = atom->omega;
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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 (mu[i][3] > 0.0) {
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g[0] = mu[i][0] + dtv * (omega[i][1]*mu[i][2]-omega[i][2]*mu[i][1]);
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g[1] = mu[i][1] + dtv * (omega[i][2]*mu[i][0]-omega[i][0]*mu[i][2]);
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g[2] = mu[i][2] + dtv * (omega[i][0]*mu[i][1]-omega[i][1]*mu[i][0]);
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msq = g[0]*g[0] + g[1]*g[1] + g[2]*g[2];
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scale = mu[i][3]/sqrt(msq);
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mu[i][0] = g[0]*scale;
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mu[i][1] = g[1]*scale;
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mu[i][2] = g[2]*scale;
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}
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}
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}
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/* ----------------------------------------------------------------------
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perform half-step scaling of rotatonal velocities
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-----------------------------------------------------------------------*/
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void FixNHSphere::nh_v_temp()
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{
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// standard nh_v_temp scaling
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FixNH::nh_v_temp();
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double **omega = atom->omega;
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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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for (int i = 0; i < nlocal; i++) {
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if (mask[i] & groupbit) {
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omega[i][0] *= factor_eta;
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omega[i][1] *= factor_eta;
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omega[i][2] *= factor_eta;
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}
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}
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}
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