compute_gyration.cpp
19e8c92a906elammm-master-deprecated

compute_gyration.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.
			------------------------------------------------------------------------- */

			#include "compute_gyration.h"
			#include "update.h"
			#include "group.h"
			#include "error.h"

			using namespace LAMMPS_NS;

			/* ---------------------------------------------------------------------- */

			ComputeGyration::ComputeGyration(LAMMPS lmp, int narg, char *arg) :
			Compute(lmp, narg, arg)
			{
			if (narg != 3) error->all(FLERR,"Illegal compute gyration command");

			scalar_flag = 1;
			extscalar = 0;
			}

			/* ---------------------------------------------------------------------- */

			void ComputeGyration::init()
			{
			masstotal = group->mass(igroup);
			}

			/* ---------------------------------------------------------------------- */

			double ComputeGyration::compute_scalar()
			{
			invoked_scalar = update->ntimestep;

			double xcm[3];
			group->xcm(igroup,masstotal,xcm);
			scalar = group->gyration(igroup,masstotal,xcm);
			return scalar;
			}