src/gromacs/mdlib/rf_util.cpp

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  38 #include "gmxpre.h"
  39
  40 #include "rf_util.h"
  41
  42 #include <cmath>
  43
  44 #include "gromacs/math/functions.h"
  45 #include "gromacs/math/units.h"
  46 #include "gromacs/math/vec.h"
  47 #include "gromacs/mdtypes/forcerec.h"
  48 #include "gromacs/mdtypes/inputrec.h"
  49 #include "gromacs/mdtypes/md_enums.h"
  50 #include "gromacs/topology/topology.h"
  51 #include "gromacs/utility/fatalerror.h"
  52 #include "gromacs/utility/pleasecite.h"
  53
  54 void calc_rffac(FILE* fplog, real eps_r, real eps_rf, real Rc, real* krf, real* crf)
  55 {
  56     /* eps == 0 signals infinite dielectric */
  57     if (eps_rf == 0)
  58     {
  59         *krf = 1 / (2 * Rc * Rc * Rc);
  60     }
  61     else
  62     {
  63         *krf = (eps_rf - eps_r) / (2 * eps_rf + eps_r) / (Rc * Rc * Rc);
  64     }
  65     *crf = 1 / Rc + *krf * Rc * Rc;
  66
  67     if (fplog)
  68     {
  69         fprintf(fplog,
  70                 "%s:\n"
  71                 "epsRF = %g, rc = %g, krf = %g, crf = %g, epsfac = %g\n",
  72                 eel_names[eelRF], eps_rf, Rc, *krf, *crf, ONE_4PI_EPS0 / eps_r);
  73         // Make sure we don't lose resolution in pow() by casting real arg to double
  74         real rmin = gmx::invcbrt(static_cast<double>(*krf * 2.0));
  75         fprintf(fplog, "The electrostatics potential has its minimum at r = %g\n", rmin);
  76     }
  77 }