diff --git a/src/USER-MISC/README b/src/USER-MISC/README
index ba19f77ac0546ff172955cf4261cf48e992049ec..8e83a4414f14e826d1f0d5a87d7c84845d9107af 100644
--- a/src/USER-MISC/README
+++ b/src/USER-MISC/README
@@ -37,6 +37,8 @@ dihedral_style table, Andrew Jewett, jewett.aij@gmail.com, 10 Jan 12
fix addtorque, Laurent Joly (U Lyon), ljoly.ulyon at gmail.com, 8 Aug 11
fix imd, Axel Kohlmeyer, akohlmey at gmail.com, 9 Nov 2009
fix smd, Axel Kohlmeyer, akohlmey at gmail.com, 19 May 2008
+fix ti/rs, Rodrigo Freitas (Unicamp/Brazil), rodrigohb at gmail.com, 7 Nov 2013
+fix ti/spring, Rodrigo Freitas (Unicamp/Brazil), rodrigohb at gmail.com, 7 Nov 2013
improper_style cossq, Georgios Vogiatzis, gvog at chemeng.ntua.gr, 25 May 12
improper_style fourier, Loukas Peristeras, loukas.peristeras at scienomics.com, 27 Oct 12
improper_style ring, Georgios Vogiatzis, gvog at chemeng.ntua.gr, 25 May 12
diff --git a/src/USER-MISC/fix_ti_rs.cpp b/src/USER-MISC/fix_ti_rs.cpp
new file mode 100755
index 0000000000000000000000000000000000000000..8ca845c87f24c48a6a31b2d17b02b532f8a4e779
--- /dev/null
+++ b/src/USER-MISC/fix_ti_rs.cpp
@@ -0,0 +1,197 @@
+/* -------------------------------------------------------------------------
+ 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 authors:
+ Rodrigo Freitas (Unicamp/Brazil) - rodrigohb@gmail.com
+ Maurice de Koning (Unicamp/Brazil) - dekoning@ifi.unicamp.br
+------------------------------------------------------------------------- */
+
+#include "stdlib.h"
+#include "string.h"
+#include "math.h"
+#include "fix_ti_rs.h"
+#include "atom.h"
+#include "update.h"
+#include "respa.h"
+#include "error.h"
+
+using namespace LAMMPS_NS;
+using namespace FixConst;
+
+/* ---------------------------------------------------------------------- */
+
+// Class constructor initialize all variables.
+
+FixTIRS::FixTIRS(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
+{
+ // Checking the input information.
+ if (narg < 7 || narg > 9) error->all(FLERR,"Illegal fix ti/rs command");
+
+ // Fix flags.
+ vector_flag = 1;
+ size_vector = 2;
+ global_freq = 1;
+ extvector = 1;
+
+ // Time variables.
+ t_switch = atof(arg[5]);
+ t_equil = atof(arg[6]);
+ t0 = update->ntimestep;
+ if (t_switch < 0.0) error->all(FLERR,"Illegal fix ti/rs command");
+ if (t_equil < 0.0) error->all(FLERR,"Illegal fix ti/rs command");
+
+ // Coupling parameter limits and initialization.
+ l_initial = atof(arg[3]);
+ l_final = atof(arg[4]);
+ sf = 1;
+ if (narg > 7) {
+ if (strcmp(arg[7], "function") == 0) sf = atoi(arg[8]);
+ else error->all(FLERR,"Illegal fix ti/rs switching function");
+ if ((sf<1) || (sf>3))
+ error->all(FLERR,"Illegal fix ti/rs switching function");
+ }
+ lambda = switch_func(0);
+ dlambda = dswitch_func(0);
+}
+
+/* ---------------------------------------------------------------------- */
+
+FixTIRS::~FixTIRS()
+{
+ // unregister callbacks to this fix from Atom class
+ atom->delete_callback(id,0);
+ atom->delete_callback(id,1);
+}
+
+/* ---------------------------------------------------------------------- */
+
+int FixTIRS::setmask()
+{
+ int mask = 0;
+ mask |= INITIAL_INTEGRATE;
+ mask |= POST_FORCE;
+ return mask;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTIRS::init()
+{
+ if (strstr(update->integrate_style,"respa"))
+ nlevels_respa = ((Respa *) update->integrate)->nlevels;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTIRS::setup(int vflag)
+{
+ if (strstr(update->integrate_style,"verlet"))
+ post_force(vflag);
+ else {
+ ((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
+ post_force_respa(vflag,nlevels_respa-1,0);
+ ((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
+ }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTIRS::min_setup(int vflag)
+{
+ post_force(vflag);
+}
+
+
+/* ---------------------------------------------------------------------- */
+
+void FixTIRS::post_force(int vflag)
+{
+
+ int *mask = atom->mask;
+ int nlocal = atom->nlocal;
+ double **f = atom->f;
+
+ // Scaling forces.
+ for (int i = 0; i < nlocal; i++) {
+ if (mask[i] & groupbit) {
+ f[i][0] = lambda * f[i][0];
+ f[i][1] = lambda * f[i][1];
+ f[i][2] = lambda * f[i][2];
+ }
+ }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTIRS::post_force_respa(int vflag, int ilevel, int iloop)
+{
+ if (ilevel == nlevels_respa-1) post_force(vflag);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTIRS::min_post_force(int vflag)
+{
+ post_force(vflag);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTIRS::initial_integrate(int vflag)
+{
+ // Update the coupling parameter value.
+ double t = update->ntimestep - (t0+t_equil);
+
+ if( (t >= 0) && (t <= t_switch) ) {
+ lambda = switch_func(t/t_switch);
+ dlambda = dswitch_func(t/t_switch);
+ }
+
+ if( (t >= t_equil+t_switch) && (t <= (t_equil+2*t_switch)) ) {
+ lambda = switch_func(1.0 - (t - t_switch - t_equil)/t_switch);
+ dlambda = - dswitch_func(1.0 - (t - t_switch - t_equil)/t_switch);
+ }
+}
+
+/* ---------------------------------------------------------------------- */
+
+double FixTIRS::compute_vector(int n)
+{
+ linfo[0] = lambda;
+ linfo[1] = dlambda;
+ return linfo[n];
+}
+
+/* ---------------------------------------------------------------------- */
+
+double FixTIRS::switch_func(double t)
+{
+ if (sf == 2) return l_initial / (1 + t * (l_initial/l_final - 1));
+ if (sf == 3) return l_initial / (1 + log2(1+t) * (l_initial/l_final - 1));
+
+ // Default option is sf = 1.
+ return l_initial + (l_final - l_initial) * t;
+}
+
+/* ---------------------------------------------------------------------- */
+
+double FixTIRS::dswitch_func(double t)
+{
+ double aux = (1.0/l_initial - 1.0/l_final);
+ if (sf == 2) return lambda * lambda * aux / t_switch;
+ if (sf == 3) return lambda * lambda * aux / (t_switch * log(2) * (1 + t));
+
+ // Default option is sf = 1.
+ return (l_final-l_initial)/t_switch;
+}
diff --git a/src/USER-MISC/fix_ti_rs.h b/src/USER-MISC/fix_ti_rs.h
new file mode 100755
index 0000000000000000000000000000000000000000..f0c8bdbe904d86f4989d77d2ebcefff6b6b2418b
--- /dev/null
+++ b/src/USER-MISC/fix_ti_rs.h
@@ -0,0 +1,60 @@
+/* ----------------------------------------------------------------------
+ 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.
+------------------------------------------------------------------------- */
+
+#ifdef FIX_CLASS
+
+FixStyle(ti/rs,FixTIRS)
+
+#else
+
+#ifndef LMP_FIX_TI_RS_H
+#define LMP_FIX_TI_RS_H
+
+#include "fix.h"
+
+namespace LAMMPS_NS {
+
+class FixTIRS : public Fix {
+ public:
+ FixTIRS(class LAMMPS *, int, char **);
+ ~FixTIRS();
+ int setmask();
+ void init();
+ void setup(int);
+ void min_setup(int);
+ void post_force(int);
+ void post_force_respa(int, int, int);
+ void min_post_force(int);
+ virtual void initial_integrate(int);
+ double compute_vector(int);
+
+ private:
+ double switch_func(double);
+ double dswitch_func(double);
+
+ double lambda; // Coupling parameter.
+ double dlambda; // Lambda variation with t.
+ double l_initial; // Lambda initial value.
+ double l_final; // Lambda final value.
+ double linfo[2]; // Current lambda status.
+ int t_switch; // Total switching steps.
+ int t_equil; // Equilibration time.
+ int t0; // Initial time.
+ int sf; // Switching function option.
+ int nlevels_respa;
+};
+
+}
+
+#endif
+#endif
diff --git a/src/USER-MISC/fix_ti_spring.cpp b/src/USER-MISC/fix_ti_spring.cpp
new file mode 100755
index 0000000000000000000000000000000000000000..ecf76fba8a6b6084d0aac0291f3a6aa2ee7a6a29
--- /dev/null
+++ b/src/USER-MISC/fix_ti_spring.cpp
@@ -0,0 +1,359 @@
+/* -------------------------------------------------------------------------
+ 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 authors:
+ Rodrigo Freitas (Unicamp/Brazil) - rodrigohb@gmail.com
+ Maurice de Koning (Unicamp/Brazil) - dekoning@ifi.unicamp.br
+------------------------------------------------------------------------- */
+
+#include "stdlib.h"
+#include "string.h"
+#include "fix_ti_spring.h"
+#include "atom.h"
+#include "update.h"
+#include "domain.h"
+#include "respa.h"
+#include "memory.h"
+#include "error.h"
+
+using namespace LAMMPS_NS;
+using namespace FixConst;
+
+/* ---------------------------------------------------------------------- */
+
+FixTISpring::FixTISpring(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg) {
+
+ if (narg < 6 || narg > 8)
+ error->all(FLERR,"Illegal fix ti/spring command");
+
+ // Flags.
+ restart_peratom = 1;
+ scalar_flag = 1;
+ vector_flag = 1;
+ size_vector = 2;
+ global_freq = 1;
+ extscalar = 1;
+ extvector = 1;
+
+ // Spring constant.
+ k = atof(arg[3]);
+ espring = 0.0;
+ if (k <= 0.0) error->all(FLERR,"Illegal fix ti/spring command");
+
+ // Initial position.
+ xoriginal = NULL;
+ grow_arrays(atom->nmax);
+ atom->add_callback(0);
+ atom->add_callback(1);
+
+ double **x = atom->x;
+ int *mask = atom->mask;
+ tagint *image = atom->image;
+ int nlocal = atom->nlocal;
+
+ for (int i = 0; i < nlocal; i++) {
+ if (mask[i] & groupbit) domain->unmap(x[i], image[i], xoriginal[i]);
+ else xoriginal[i][0] = xoriginal[i][1] = xoriginal[i][2] = 0.0;
+ }
+
+ // Time variables.
+ t_switch = atof(arg[4]); // Switching time.
+ t_equil = atof(arg[5]); // Equilibration time.
+ t0 = update->ntimestep; // Initial time.
+ if (t_switch < 0.0) error->all(FLERR,"Illegal fix ti/spring command");
+ if (t_equil < 0.0) error->all(FLERR,"Illegal fix ti/spring command");
+
+ // Coupling parameter initialization.
+ sf = 1;
+ if (narg > 6) {
+ if (strcmp(arg[6], "function") == 0) sf = atoi(arg[7]);
+ else error->all(FLERR,"Illegal fix ti/spring switching function");
+ if ((sf!=1) && (sf!=2))
+ error->all(FLERR,"Illegal fix ti/spring switching function");
+ }
+ lambda = switch_func(0);
+ dlambda = dswitch_func(0);
+}
+
+/* ---------------------------------------------------------------------- */
+
+FixTISpring::~FixTISpring()
+{
+ // unregister callbacks to this fix from Atom class
+ atom->delete_callback(id,0);
+ atom->delete_callback(id,1);
+
+ // delete locally stored array
+ memory->destroy(xoriginal);
+}
+
+/* ---------------------------------------------------------------------- */
+
+int FixTISpring::setmask()
+{
+ int mask = 0;
+ mask |= INITIAL_INTEGRATE;
+ mask |= POST_FORCE;
+ mask |= POST_FORCE_RESPA;
+ mask |= MIN_POST_FORCE;
+ mask |= THERMO_ENERGY;
+ return mask;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTISpring::init()
+{
+ if (strstr(update->integrate_style,"respa"))
+ nlevels_respa = ((Respa *) update->integrate)->nlevels;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTISpring::setup(int vflag)
+{
+ if (strstr(update->integrate_style,"verlet"))
+ post_force(vflag);
+ else {
+ ((Respa *) update->integrate)->copy_flevel_f(nlevels_respa-1);
+ post_force_respa(vflag,nlevels_respa-1,0);
+ ((Respa *) update->integrate)->copy_f_flevel(nlevels_respa-1);
+ }
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTISpring::min_setup(int vflag)
+{
+ post_force(vflag);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTISpring::post_force(int vflag)
+{
+
+ // If on the first equilibration do not calculate forces.
+ int t = update->ntimestep - t0;
+ espring = 0.0;
+ if(t < t_equil) return;
+
+ double **x = atom->x;
+ double **f = atom->f;
+ int *mask = atom->mask;
+ tagint *image = atom->image;
+ int nlocal = atom->nlocal;
+
+ double dx, dy, dz;
+ double unwrap[3];
+
+ for (int i = 0; i < nlocal; i++)
+ if (mask[i] & groupbit) {
+ domain->unmap(x[i], image[i], unwrap);
+ dx = unwrap[0] - xoriginal[i][0];
+ dy = unwrap[1] - xoriginal[i][1];
+ dz = unwrap[2] - xoriginal[i][2];
+ f[i][0] = (1-lambda) * f[i][0] + lambda * (-k*dx);
+ f[i][1] = (1-lambda) * f[i][1] + lambda * (-k*dy);
+ f[i][2] = (1-lambda) * f[i][2] + lambda * (-k*dz);
+ espring += k * (dx*dx + dy*dy + dz*dz);
+ }
+
+ espring *= 0.5;
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTISpring::post_force_respa(int vflag, int ilevel, int iloop)
+{
+ if (ilevel == nlevels_respa-1) post_force(vflag);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTISpring::min_post_force(int vflag)
+{
+ post_force(vflag);
+}
+
+/* ---------------------------------------------------------------------- */
+
+void FixTISpring::initial_integrate(int vflag)
+{
+ // Update the coupling parameter value.
+ double t = update->ntimestep - (t0+t_equil);
+
+ if( (t >= 0) && (t <= t_switch) ) {
+ lambda = switch_func(t/t_switch);
+ dlambda = dswitch_func(t/t_switch);
+ }
+
+ if( (t >= t_equil+t_switch) && (t <= (t_equil+2*t_switch)) ) {
+ lambda = switch_func(1.0 - (t - t_switch - t_equil)/t_switch );
+ dlambda = - dswitch_func(1.0 - (t - t_switch - t_equil)/t_switch );
+ }
+}
+
+/* ----------------------------------------------------------------------
+ energy of stretched springs
+------------------------------------------------------------------------- */
+
+double FixTISpring::compute_scalar()
+{
+ double all;
+ MPI_Allreduce(&espring,&all,1,MPI_DOUBLE,MPI_SUM,world);
+ return all;
+}
+
+/* ----------------------------------------------------------------------
+ information about coupling parameter
+------------------------------------------------------------------------- */
+
+double FixTISpring::compute_vector(int n)
+{
+ linfo[0] = lambda;
+ linfo[1] = dlambda;
+ return linfo[n];
+}
+
+/* ----------------------------------------------------------------------
+ memory usage of local atom-based array
+------------------------------------------------------------------------- */
+
+double FixTISpring::memory_usage()
+{
+ double bytes = atom->nmax*3 * sizeof(double);
+ return bytes;
+}
+
+/* ----------------------------------------------------------------------
+ allocate atom-based array
+------------------------------------------------------------------------- */
+
+void FixTISpring::grow_arrays(int nmax)
+{
+ memory->grow(xoriginal,nmax,3,"fix_ti/spring:xoriginal");
+}
+
+/* ----------------------------------------------------------------------
+ copy values within local atom-based array
+------------------------------------------------------------------------- */
+
+void FixTISpring::copy_arrays(int i, int j)
+{
+ xoriginal[j][0] = xoriginal[i][0];
+ xoriginal[j][1] = xoriginal[i][1];
+ xoriginal[j][2] = xoriginal[i][2];
+}
+
+/* ----------------------------------------------------------------------
+ pack values in local atom-based array for exchange with another proc
+------------------------------------------------------------------------- */
+
+int FixTISpring::pack_exchange(int i, double *buf)
+{
+ buf[0] = xoriginal[i][0];
+ buf[1] = xoriginal[i][1];
+ buf[2] = xoriginal[i][2];
+ return 3;
+}
+
+/* ----------------------------------------------------------------------
+ unpack values in local atom-based array from exchange with another proc
+ ------------------------------------------------------------------------- */
+
+int FixTISpring::unpack_exchange(int nlocal, double *buf)
+{
+ xoriginal[nlocal][0] = buf[0];
+ xoriginal[nlocal][1] = buf[1];
+ xoriginal[nlocal][2] = buf[2];
+ return 3;
+}
+
+/* ----------------------------------------------------------------------
+ pack values in local atom-based arrays for restart file
+------------------------------------------------------------------------- */
+
+int FixTISpring::pack_restart(int i, double *buf)
+{
+ buf[0] = 4;
+ buf[1] = xoriginal[i][0];
+ buf[2] = xoriginal[i][1];
+ buf[3] = xoriginal[i][2];
+ return 4;
+}
+
+
+/* ----------------------------------------------------------------------
+ unpack values from atom->extra array to restart the fix
+------------------------------------------------------------------------- */
+
+void FixTISpring::unpack_restart(int nlocal, int nth)
+{
+ double **extra = atom->extra;
+
+ // skip to Nth set of extra values
+
+ int m = 0;
+ for (int i = 0; i < nth; i++) m += static_cast<int> (extra[nlocal][m]);
+ m++;
+
+ xoriginal[nlocal][0] = extra[nlocal][m++];
+ xoriginal[nlocal][1] = extra[nlocal][m++];
+ xoriginal[nlocal][2] = extra[nlocal][m++];
+}
+
+/* ----------------------------------------------------------------------
+ maxsize of any atom's restart data
+------------------------------------------------------------------------- */
+
+int FixTISpring::maxsize_restart()
+{
+ return 4;
+}
+
+/* ----------------------------------------------------------------------
+ size of atom nlocal's restart data
+------------------------------------------------------------------------- */
+
+int FixTISpring::size_restart(int nlocal)
+{
+ return 4;
+}
+
+/* ----------------------------------------------------------------------
+ Switching function.
+------------------------------------------------------------------------- */
+
+double FixTISpring::switch_func(double t)
+{
+ if (sf == 1) return t;
+
+ double t2 = t*t;
+ double t5 = t2*t2*t;
+ return ((70.0*t2*t2 - 315.0*t2*t + 540.0*t2 - 420.0*t + 126.0)*t5);
+}
+
+/* ----------------------------------------------------------------------
+ Switching function derivative.
+------------------------------------------------------------------------- */
+
+double FixTISpring::dswitch_func(double t)
+{
+ if(sf == 1) return 1.0/t_switch;
+
+ double t2 = t*t;
+ double t4 = t2*t2;
+ return ((630*t2*t2 - 2520*t2*t + 3780*t2 - 2520*t + 630)*t4) / t_switch;
+}
diff --git a/src/USER-MISC/fix_ti_spring.h b/src/USER-MISC/fix_ti_spring.h
new file mode 100755
index 0000000000000000000000000000000000000000..21d7ef5d14468126c3dc1a00947840c0e891e281
--- /dev/null
+++ b/src/USER-MISC/fix_ti_spring.h
@@ -0,0 +1,88 @@
+/* ----------------------------------------------------------------------
+ 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.
+------------------------------------------------------------------------- */
+
+#ifdef FIX_CLASS
+
+FixStyle(ti/spring,FixTISpring)
+
+#else
+
+#ifndef LMP_FIX_TI_SPRING_H
+#define LMP_FIX_TI_SPRING_H
+
+#include "fix.h"
+
+namespace LAMMPS_NS {
+
+class FixTISpring : public Fix {
+ public:
+ FixTISpring(class LAMMPS *, int, char **);
+ ~FixTISpring();
+ int setmask();
+ void init();
+ void setup(int);
+ void min_setup(int);
+ void post_force(int);
+ void post_force_respa(int, int, int);
+ void min_post_force(int);
+ void initial_integrate(int);
+ double compute_scalar();
+ double compute_vector(int);
+
+ double memory_usage();
+ void grow_arrays(int);
+ void copy_arrays(int, int);
+ int pack_exchange(int, double *);
+ int unpack_exchange(int, double *);
+ int pack_restart(int, double *);
+ void unpack_restart(int, int);
+ int size_restart(int);
+ int maxsize_restart();
+
+ private:
+ double switch_func(double); // Switching function.
+ double dswitch_func(double); // Switching function derivative.
+
+ double k; // Spring constant.
+ double espring; // Springs energies.
+ double **xoriginal; // Original coords of atoms.
+ double lambda; // Coupling parameter.
+ double dlambda; // Lambda variation with t.
+ double linfo[2]; // Current lambda status.
+ int t_switch; // Total switching steps.
+ int t_equil; // Equilibration time.
+ int t0; // Initial time.
+ int sf; // Switching function option.
+ int nlevels_respa;
+};
+
+}
+
+#endif
+#endif
+
+/* ERROR/WARNING messages:
+
+E: Illegal ... command
+
+Self-explanatory. Check the input script syntax and compare to the
+documentation for the command. You can use -echo screen as a
+command-line option when running LAMMPS to see the offending line.
+
+E: Illegal fix ti/spring switching function
+
+Self-explanatory. Check the input script syntax and compare to the
+documentation for the command. You can use -echo screen as a
+command-line option when running LAMMPS to see the offending line.
+
+*/