Added a Morse potential option to 'fix wall/region' (101948ce) · Commits · 郑智淋 / lammps

src/fix_wall_region.cpp

+30 −4

Original line number	Diff line number	Diff line
		@@ -31,7 +31,7 @@ using namespace LAMMPS_NS;
		using namespace FixConst;
		using namespace MathConst;

		enum{LJ93,LJ126,LJ1043,COLLOID,HARMONIC};
		enum{LJ93,LJ126,LJ1043,MORSE,COLLOID,HARMONIC};

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

		@@ -39,7 +39,7 @@ FixWallRegion::FixWallRegion(LAMMPS lmp, int narg, char *arg) :
		Fix(lmp, narg, arg),
		idregion(NULL)
		{
		if (narg != 8) error->all(FLERR,"Illegal fix wall/region command");
		if (narg < 8) error->all(FLERR,"Illegal fix wall/region command");

		scalar_flag = 1;
		vector_flag = 1;
		@@ -63,6 +63,7 @@ FixWallRegion::FixWallRegion(LAMMPS lmp, int narg, char *arg) :
		if (strcmp(arg[4],"lj93") == 0) style = LJ93;
		else if (strcmp(arg[4],"lj126") == 0) style = LJ126;
		else if (strcmp(arg[4],"lj1043") == 0) style = LJ1043;
		else if (strcmp(arg[4],"morse") == 0) style = MORSE;
		else if (strcmp(arg[4],"colloid") == 0) style = COLLOID;
		else if (strcmp(arg[4],"harmonic") == 0) style = HARMONIC;
		else error->all(FLERR,"Illegal fix wall/region command");
		@@ -73,6 +74,14 @@ FixWallRegion::FixWallRegion(LAMMPS lmp, int narg, char *arg) :
		sigma = force->numeric(FLERR,arg[6]);
		cutoff = force->numeric(FLERR,arg[7]);

		if (style == MORSE) {
		if (narg != 9)
		error->all(FLERR,"Illegal fix wall/region command");
		else
		alpha = force->numeric(FLERR,arg[8]);
		} else if (narg != 8)
		error->all(FLERR,"Illegal fix wall/region command");

		if (cutoff <= 0.0) error->all(FLERR,"Fix wall/region cutoff <= 0.0");

		eflag = 0;
		@@ -157,12 +166,15 @@ void FixWallRegion::init()
		coeff5 = coeff1 * 10.0;
		coeff6 = coeff2 * 4.0;
		coeff7 = coeff3 * 3.0;

		double rinv = 1.0/cutoff;
		double r2inv = rinv*rinv;
		double r4inv = r2inv*r2inv;
		offset = coeff1r4invr4invr2inv - coeff2r4inv -
		coeff3*pow(cutoff+coeff4,-3.0);
		} else if (style == MORSE) {
		coeff1 = 2 * epsilon * alpha;
		double alpha_dr = -alpha * (cutoff - sigma);
		offset = epsilon * (exp(2.0alpha_dr) - 2.0exp(alpha_dr));
		} else if (style == COLLOID) {
		coeff1 = -4.0/315.0 * epsilon * pow(sigma,6.0);
		coeff2 = -2.0/3.0 * epsilon;
		@@ -253,6 +265,7 @@ void FixWallRegion::post_force(int vflag)
		if (style == LJ93) lj93(region->contact[m].r);
		else if (style == LJ126) lj126(region->contact[m].r);
		else if (style == LJ1043) lj1043(region->contact[m].r);
		else if (style == MORSE) morse(region->contact[m].r);
		else if (style == COLLOID) colloid(region->contact[m].r,radius[i]);
		else harmonic(region->contact[m].r);

		@@ -287,7 +300,7 @@ void FixWallRegion::post_force(int vflag)

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

		void FixWallRegion::post_force_respa(int vflag, int ilevel, int /iloop/)
		void FixWallRegion::post_force_respa(int vflag, int ilevel, int iloop)
		{
		if (ilevel == ilevel_respa) post_force(vflag);
		}
		@@ -375,6 +388,19 @@ void FixWallRegion::lj1043(double r)
		coeff3*pow(r+coeff4,-3.0) - offset;
		}

		/* ----------------------------------------------------------------------
		Morse interaction for particle with wall
		compute eng and fwall = magnitude of wall force
		------------------------------------------------------------------------- */

		void FixWallRegion::morse(double r)
		{
		double dr = r - sigma;
		double dexp = exp(-alpha * dr);
		fwall = coeff1 * (dexp*dexp - dexp) / r;
		eng = epsilon * (dexpdexp - 2.0dexp) - offset;
		}

		/* ----------------------------------------------------------------------
		colloid interaction for finite-size particle of rad with wall
		compute eng and fwall = magnitude of wall force

src/fix_wall_region.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -41,6 +41,7 @@ class FixWallRegion : public Fix {
		private:
		int style,iregion;
		double epsilon,sigma,cutoff;
		double alpha;
		int eflag;
		double ewall[4],ewall_all[4];
		int ilevel_respa;
		@@ -53,6 +54,7 @@ class FixWallRegion : public Fix {
		void lj93(double);
		void lj126(double);
		void lj1043(double);
		void morse(double);
		void colloid(double, double);
		void harmonic(double);
		};

Admin message