forked from lijiext/lammps
Modifed ZBL to accomodate mixing
git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@14047 f3b2605a-c512-4ea7-a41b-209d697bcdaa
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athomps
parent
ca55525283
commit
fe3c6670f6
138
src/pair_zbl.cpp
138
src/pair_zbl.cpp
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@ -199,11 +199,14 @@ void PairZBL::settings(int narg, char **arg)
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/* ----------------------------------------------------------------------
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set coeffs for one or more type pairs
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------------------------------------------------------------------------- */
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void PairZBL::coeff(int narg, char **arg)
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{
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if (narg != 3)
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double z_one, z_two;
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if (narg != 4)
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error->all(FLERR,"Incorrect args for pair coefficients");
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if (!allocated) allocate();
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@ -213,7 +216,8 @@ void PairZBL::coeff(int narg, char **arg)
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int jlo,jhi;
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force->bounds(arg[1],atom->ntypes,jlo,jhi);
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double z_one = force->numeric(FLERR,arg[2]);
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z_one = force->numeric(FLERR,arg[2]);
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z_two = force->numeric(FLERR,arg[3]);
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// set flag for each i-j pair
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// set z-parameter only for i-i pairs
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@ -221,8 +225,13 @@ void PairZBL::coeff(int narg, char **arg)
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int count = 0;
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for (int i = ilo; i <= ihi; i++) {
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for (int j = MAX(jlo,i); j <= jhi; j++) {
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if (i == j) z[i] = z_one;
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if (i == j) {
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if (z_one != z_two)
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error->all(FLERR,"Incorrect args for pair coefficients");
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z[i] = z_one;
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}
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setflag[i][j] = 1;
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set_coeff(i, j, z_one, z_two);
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count++;
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}
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}
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@ -248,63 +257,8 @@ void PairZBL::init_style()
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double PairZBL::init_one(int i, int j)
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{
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double ainv = (pow(z[i],pzbl) + pow(z[j],pzbl))/(a0*force->angstrom);
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d1a[i][j] = d1*ainv;
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d2a[i][j] = d2*ainv;
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d3a[i][j] = d3*ainv;
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d4a[i][j] = d4*ainv;
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zze[i][j] = z[i]*z[j]*force->qqr2e*force->qelectron*force->qelectron;
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d1a[j][i] = d1a[i][j];
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d2a[j][i] = d2a[i][j];
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d3a[j][i] = d3a[i][j];
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d4a[j][i] = d4a[i][j];
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zze[j][i] = zze[i][j];
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// e = t^3 (sw3 + sw4*t) + sw5
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// = A/3*t^3 + B/4*t^4 + C
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// sw3 = A/3
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// sw4 = B/4
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// sw5 = C
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// dedr = t^2 (sw1 + sw2*t)
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// = A*t^2 + B*t^3
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// sw1 = A
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// sw2 = B
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// de2dr2 = 2*A*t + 3*B*t^2
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// Require that at t = tc:
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// e = -Fc
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// dedr = -Fc'
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// d2edr2 = -Fc''
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// Hence:
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// A = (-3Fc' + tc*Fc'')/tc^2
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// B = ( 2Fc' - tc*Fc'')/tc^3
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// C = -Fc + tc/2*Fc' - tc^2/12*Fc''
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double tc = cut_global - cut_inner;
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double fc = e_zbl(cut_global, i, j);
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double fcp = dzbldr(cut_global, i, j);
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double fcpp = d2zbldr2(cut_global, i, j);
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double swa = (-3.0*fcp + tc*fcpp)/(tc*tc);
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double swb = ( 2.0*fcp - tc*fcpp)/(tc*tc*tc);
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double swc = -fc + (tc/2.0)*fcp - (tc*tc/12.0)*fcpp;
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sw1[i][j] = swa;
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sw2[i][j] = swb;
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sw3[i][j] = swa/3.0;
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sw4[i][j] = swb/4.0;
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sw5[i][j] = swc;
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sw1[j][i] = sw1[i][j];
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sw2[j][i] = sw2[i][j];
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sw3[j][i] = sw3[i][j];
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sw4[j][i] = sw4[i][j];
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sw5[j][i] = sw5[i][j];
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if (setflag[i][j] == 0)
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set_coeff(i, j, z[i], z[j]);
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return cut_global;
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}
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@ -434,3 +388,67 @@ double PairZBL::d2zbldr2(double r, int i, int j) {
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return result;
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}
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/* ----------------------------------------------------------------------
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calculate the i,j entries in the various coeff arrays
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------------------------------------------------------------------------- */
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void PairZBL::set_coeff(int i, int j, double zi, double zj)
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{
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double ainv = (pow(zi,pzbl) + pow(zj,pzbl))/(a0*force->angstrom);
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d1a[i][j] = d1*ainv;
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d2a[i][j] = d2*ainv;
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d3a[i][j] = d3*ainv;
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d4a[i][j] = d4*ainv;
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zze[i][j] = zi*zj*force->qqr2e*force->qelectron*force->qelectron;
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d1a[j][i] = d1a[i][j];
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d2a[j][i] = d2a[i][j];
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d3a[j][i] = d3a[i][j];
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d4a[j][i] = d4a[i][j];
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zze[j][i] = zze[i][j];
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// e = t^3 (sw3 + sw4*t) + sw5
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// = A/3*t^3 + B/4*t^4 + C
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// sw3 = A/3
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// sw4 = B/4
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// sw5 = C
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// dedr = t^2 (sw1 + sw2*t)
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// = A*t^2 + B*t^3
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// sw1 = A
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// sw2 = B
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// de2dr2 = 2*A*t + 3*B*t^2
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// Require that at t = tc:
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// e = -Fc
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// dedr = -Fc'
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// d2edr2 = -Fc''
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// Hence:
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// A = (-3Fc' + tc*Fc'')/tc^2
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// B = ( 2Fc' - tc*Fc'')/tc^3
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// C = -Fc + tc/2*Fc' - tc^2/12*Fc''
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double tc = cut_global - cut_inner;
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double fc = e_zbl(cut_global, i, j);
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double fcp = dzbldr(cut_global, i, j);
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double fcpp = d2zbldr2(cut_global, i, j);
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double swa = (-3.0*fcp + tc*fcpp)/(tc*tc);
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double swb = ( 2.0*fcp - tc*fcpp)/(tc*tc*tc);
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double swc = -fc + (tc/2.0)*fcp - (tc*tc/12.0)*fcpp;
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sw1[i][j] = swa;
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sw2[i][j] = swb;
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sw3[i][j] = swa/3.0;
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sw4[i][j] = swb/4.0;
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sw5[i][j] = swc;
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sw1[j][i] = sw1[i][j];
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sw2[j][i] = sw2[i][j];
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sw3[j][i] = sw3[i][j];
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sw4[j][i] = sw4[i][j];
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sw5[j][i] = sw5[i][j];
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}
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@ -46,6 +46,7 @@ class PairZBL : public Pair {
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double e_zbl(double, int, int);
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double dzbldr(double, int, int);
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double d2zbldr2(double, int, int);
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void set_coeff(int, int, double, double);
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};
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namespace PairZBLConstants {
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