print single warning when some rho[i] exceeded rhomax of the current EAM potential

doc/src/pair_eam.rst

@@ -140,6 +140,20 @@ The OpenKIM Project at
 provides EAM potentials that can be used directly in LAMMPS with the
 :doc:`kim command <kim_commands>` interface.
 
+.. warning::
+
+   The EAM potential files tabulate the embedding energy as a function
+   of the local electron density :math:`\rho`.  When atoms get too
+   close, this electron density may exceed the range for which the
+   embedding energy was tabulated for.  For simplicity and to avoid
+   errors during equilibration of randomized geometries, LAMMPS will
+   assume a linearly increasing embedding energy for electron densities
+   beyond the maximum tabulated value.  This usually means that the EAM
+   model is not a good model for the kind of system under investigation.
+   LAMMPS will print a single warning when this happens.  It may be
+   harmless at the beginning of an equilibration but would be a big
+   concern for accuracy if it happens during production runs.
+
 ----------
 
 For style *eam*, potential values are read from a file that is in the

src/INTEL/pair_eam_intel.cpp

@@ -234,7 +234,7 @@ void PairEAMIntel::eval(const int offload, const int vflag,
   const int istride = fc.rhor_istride();
   const int jstride = fc.rhor_jstride();
   const int fstride = fc.frho_stride();
-
+  int beyond_rhomax = 0;
   {
     #if defined(__MIC__) && defined(_LMP_INTEL_OFFLOAD)
     *timer_compute = MIC_Wtime();
@@ -453,7 +453,10 @@ void PairEAMIntel::eval(const int offload, const int vflag,
         if (EFLAG) {
           flt_t phi = ((frho_spline_e[ioff].a*p + frho_spline_e[ioff].b)*p +
                        frho_spline_e[ioff].c)*p + frho_spline_e[ioff].d;
-          if (rho[i] > frhomax) phi += fp_f[i] * (rho[i]-frhomax);
+          if (rho[i] > frhomax) {
+            phi += fp_f[i] * (rho[i]-frhomax);
+            beyond_rhomax = 1;
+          }
           if (!ONETYPE) {
             const int ptr_off=itype*ntypes + itype;
             oscale = scale_f[ptr_off];
@@ -653,6 +656,16 @@ void PairEAMIntel::eval(const int offload, const int vflag,
   else
     fix->stop_watch(TIME_HOST_PAIR);
 
+  if (EFLAG && (exceeded_rhomax >= 0)) {
+    MPI_Allreduce(&beyond_rhomax, &exceeded_rhomax, 1, MPI_INT, MPI_MAX, world);
+    if (exceeded_rhomax > 0) {
+      if (comm->me == 0)
+        error->warning(FLERR, "Local rho[i] exceeded rhomax of EAM potential table. "
+                       "Computed embedding term is unreliable.");
+      exceeded_rhomax = -1;
+    }
+  }
+
   if (EFLAG || vflag)
     fix->add_result_array(f_start, ev_global, offload, eatom, 0, vflag);
   else
@@ -849,4 +862,3 @@ void PairEAMIntel::unpack_forward_comm(int n, int first, double *buf,
   last = first + n;
   for (i = first; i < last; i++) fp_f[i] = buf[m++];
 }
-

src/MANYBODY/pair_eam.cpp

@@ -43,6 +43,7 @@ PairEAM::PairEAM(LAMMPS *lmp) : Pair(lmp)
   unit_convert_flag = utils::get_supported_conversions(utils::ENERGY);
 
   nmax = 0;
+  exceeded_rhomax = 0;
   rho = nullptr;
   fp = nullptr;
   numforce = nullptr;
@@ -145,6 +146,7 @@ void PairEAM::compute(int eflag, int vflag)
   double *coeff;
   int *ilist,*jlist,*numneigh,**firstneigh;
 
+  int beyond_rhomax = 0;
   evdwl = 0.0;
   ev_init(eflag,vflag);
 
@@ -237,7 +239,9 @@ void PairEAM::compute(int eflag, int vflag)
     fp[i] = (coeff[0]*p + coeff[1])*p + coeff[2];
     if (eflag) {
       phi = ((coeff[3]*p + coeff[4])*p + coeff[5])*p + coeff[6];
-      if (rho[i] > rhomax) phi += fp[i] * (rho[i]-rhomax);
+      if (rho[i] > rhomax) {
+        phi += fp[i] * (rho[i]-rhomax);
+      }
       phi *= scale[type[i]][type[i]];
       if (eflag_global) eng_vdwl += phi;
       if (eflag_atom) eatom[i] += phi;
@@ -322,6 +326,16 @@ void PairEAM::compute(int eflag, int vflag)
     }
   }
 
+  if (eflag && (exceeded_rhomax >= 0)) {
+    MPI_Allreduce(&beyond_rhomax, &exceeded_rhomax, 1, MPI_INT, MPI_MAX, world);
+    if (exceeded_rhomax > 0) {
+      if (comm->me == 0)
+        error->warning(FLERR, "Local rho[i] exceeded rhomax of EAM potential table. "
+                       "Computed embedding term is unreliable.");
+      exceeded_rhomax = -1;
+    }
+  }
+
   if (vflag_fdotr) virial_fdotr_compute();
 }
 
@@ -424,6 +438,8 @@ void PairEAM::init_style()
 
   neighbor->add_request(this);
   embedstep = -1;
+
+  exceeded_rhomax = 0;
 }
 
 /* ----------------------------------------------------------------------

src/MANYBODY/pair_eam.h

@@ -63,7 +63,8 @@ class PairEAM : public Pair {
   void swap_eam(double *, double **) override;
 
  protected:
-  int nmax;    // allocated size of per-atom arrays
+  int nmax;               // allocated size of per-atom arrays
+  int exceeded_rhomax;    // 0 or 1 when rho[i] exceeded rhomax, -1 when not to check
   double cutforcesq;
   double **scale;
   bigint embedstep;    // timestep, the embedding term was computed

src/OPENMP/pair_eam_omp.cpp

@@ -17,6 +17,7 @@
 
 #include "atom.h"
 #include "comm.h"
+#include "error.h"
 #include "force.h"
 #include "memory.h"
 #include "neigh_list.h"
@@ -102,6 +103,7 @@ void PairEAMOMP::eval(int iifrom, int iito, ThrData * const thr)
   double *coeff;
   int *ilist,*jlist,*numneigh,**firstneigh;
 
+  int beyond_rhomax = 0;
   evdwl = 0.0;
 
   const auto * _noalias const x = (dbl3_t *) atom->x[0];
@@ -203,7 +205,10 @@ void PairEAMOMP::eval(int iifrom, int iito, ThrData * const thr)
     fp[i] = (coeff[0]*p + coeff[1])*p + coeff[2];
     if (EFLAG) {
       phi = ((coeff[3]*p + coeff[4])*p + coeff[5])*p + coeff[6];
-      if (rho[i] > rhomax) phi += fp[i] * (rho[i]-rhomax);
+      if (rho[i] > rhomax) {
+        phi += fp[i] * (rho[i]-rhomax);
+        beyond_rhomax = 1;
+      }
       e_tally_thr(this, i, i, nlocal, NEWTON_PAIR, scale[type[i]][type[i]]*phi, 0.0, thr);
     }
   }
@@ -298,6 +303,16 @@ void PairEAMOMP::eval(int iifrom, int iito, ThrData * const thr)
     f[i].y += fytmp;
     f[i].z += fztmp;
   }
+
+  if (EFLAG && (exceeded_rhomax >= 0)) {
+    MPI_Allreduce(&beyond_rhomax, &exceeded_rhomax, 1, MPI_INT, MPI_MAX, world);
+    if (exceeded_rhomax > 0) {
+      if (comm->me == 0)
+        error->warning(FLERR, "Local rho[i] exceeded rhomax of EAM potential table. "
+                       "Computed embedding term is unreliable.");
+      exceeded_rhomax = -1;
+    }
+  }
 }
 
 /* ---------------------------------------------------------------------- */

src/OPT/pair_eam_opt.cpp

@@ -23,6 +23,7 @@
 
 #include "atom.h"
 #include "comm.h"
+#include "error.h"
 #include "force.h"
 #include "memory.h"
 #include "neigh_list.h"
@@ -118,6 +119,7 @@ template <int EVFLAG, int EFLAG, int NEWTON_PAIR> void PairEAMOpt::eval()
 
   int ntypes = atom->ntypes;
   int ntypes2 = ntypes * ntypes;
+  int beyond_rhomax = 0;
 
   auto *_noalias fast_alpha =
       (fast_alpha_t *) malloc((size_t) ntypes2 * (nr + 1) * sizeof(fast_alpha_t));
@@ -251,7 +253,10 @@ template <int EVFLAG, int EFLAG, int NEWTON_PAIR> void PairEAMOpt::eval()
     fp[i] = (coeff[0] * p + coeff[1]) * p + coeff[2];
     if (EFLAG) {
       double phi = ((coeff[3] * p + coeff[4]) * p + coeff[5]) * p + coeff[6];
-      if (rho[i] > rhomax) phi += fp[i] * (rho[i] - rhomax);
+      if (rho[i] > rhomax) {
+        phi += fp[i] * (rho[i] - rhomax);
+        beyond_rhomax = 1;
+      }
       phi *= scale[type[i]][type[i]];
       if (eflag_global) eng_vdwl += phi;
       if (eflag_atom) eatom[i] += phi;
@@ -361,5 +366,15 @@ template <int EVFLAG, int EFLAG, int NEWTON_PAIR> void PairEAMOpt::eval()
   free(fast_gamma);
   fast_gamma = nullptr;
 
+  if (EFLAG && (exceeded_rhomax >= 0)) {
+    MPI_Allreduce(&beyond_rhomax, &exceeded_rhomax, 1, MPI_INT, MPI_MAX, world);
+    if (exceeded_rhomax > 0) {
+      if (comm->me == 0)
+        error->warning(FLERR, "Local rho[i] exceeded rhomax of EAM potential table. "
+                       "Computed embedding term is unreliable.");
+      exceeded_rhomax = -1;
+    }
+  }
+
   if (vflag_fdotr) virial_fdotr_compute();
 }