forked from lijiext/lammps
git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@1189 f3b2605a-c512-4ea7-a41b-209d697bcdaa
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sjplimp
parent
bf7903653b
commit
5d0e722080
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@ -795,7 +795,7 @@ void PPPM::deallocate()
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void PPPM::set_grid()
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{
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// see JCP 109, pg. 7698 for derivation of coefficients
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// see JCP 109, pg 7698 for derivation of coefficients
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// higher order coefficients may be computed if needed
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double **acons = memory->create_2d_double_array(8,7,"pppm:acons");
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@ -846,119 +846,91 @@ void PPPM::set_grid()
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// fluid-occupied volume used to estimate real-space error
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// zprd used rather than zprd_slab
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double hx,hy,hz;
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if (!gewaldflag)
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g_ewald = sqrt(-log(precision*sqrt(natoms*cutoff*xprd*yprd*zprd) /
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(2.0*q2))) / cutoff;
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// set optimal nx_pppm,ny_pppm,nz_pppm based on order and precision
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// nz_pppm uses extended zprd_slab instead of zprd
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double h,h1,h2,err,er1,er2,lpr;
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int ncount;
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// h = 1/g_ewald is upper bound on h such that h*g_ewald <= 1
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// reduce it until precision target is met
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if (!gridflag) {
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h = 1.0;
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h1 = 2.0;
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double err;
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hx = hy = hz = 1/g_ewald;
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ncount = 0;
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err = LARGE;
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er1 = 0.0;
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while (fabs(err) > SMALL) {
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lpr = rms(h,xprd,natoms,q2,acons);
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err = log(lpr) - log(precision);
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er2 = er1;
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er1 = err;
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h2 = h1;
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h1 = h;
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if ((er1 - er2) == 0.0) h = h1 + er1;
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else h = h1 + er1*(h2 - h1)/(er1 - er2);
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ncount++;
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if (ncount > LARGE) error->all("Cannot compute PPPM X grid spacing");
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nx_pppm = static_cast<int> (xprd/hx + 1);
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ny_pppm = static_cast<int> (yprd/hy + 1);
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nz_pppm = static_cast<int> (zprd_slab/hz + 1);
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err = rms(hx,xprd,natoms,q2,acons);
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while (err > precision) {
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err = rms(hx,xprd,natoms,q2,acons);
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nx_pppm++;
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hx = xprd/nx_pppm;
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}
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nx_pppm = static_cast<int> (xprd/h + 1);
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ncount = 0;
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err = LARGE;
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er1 = 0.0;
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while (fabs(err) > SMALL) {
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lpr = rms(h,yprd,natoms,q2,acons);
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err = log(lpr) - log(precision);
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er2 = er1;
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er1 = err;
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h2 = h1;
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h1 = h;
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if ((er1 - er2) == 0.0) h = h1 + er1;
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else h = h1 + er1*(h2 - h1)/(er1 - er2);
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ncount++;
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if (ncount > LARGE) error->all("Cannot compute PPPM Y grid spacing");
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err = rms(hy,yprd,natoms,q2,acons);
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while (err > precision) {
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err = rms(hy,yprd,natoms,q2,acons);
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ny_pppm++;
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hy = yprd/ny_pppm;
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}
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ny_pppm = static_cast<int> (yprd/h + 1);
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ncount = 0;
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err = LARGE;
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er1 = 0.0;
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while (fabs(err) > SMALL) {
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lpr = rms(h,zprd_slab,natoms,q2,acons);
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err = log(lpr) - log(precision);
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er2 = er1;
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er1 = err;
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h2 = h1;
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h1 = h;
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if ((er1 - er2) == 0.0) h = h1 + er1;
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else h = h1 + er1*(h2 - h1)/(er1 - er2);
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ncount++;
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if (ncount > LARGE) error->all("Cannot compute PPPM Z grid spacing");
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err = rms(hz,zprd_slab,natoms,q2,acons);
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while (err > precision) {
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err = rms(hz,zprd_slab,natoms,q2,acons);
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nz_pppm++;
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hz = zprd_slab/nz_pppm;
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}
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nz_pppm = static_cast<int> (zprd_slab/h + 1);
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}
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// convert grid into sizes that are factorable
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// boost grid size until it is factorable
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while (!factorable(nx_pppm)) nx_pppm++;
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while (!factorable(ny_pppm)) ny_pppm++;
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while (!factorable(nz_pppm)) nz_pppm++;
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// adjust g_ewald for new grid
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// adjust g_ewald for new grid size
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double dx = xprd/nx_pppm;
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double dy = yprd/ny_pppm;
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double dz = zprd_slab/nz_pppm;
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hx = xprd/nx_pppm;
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hy = yprd/ny_pppm;
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hz = zprd_slab/nz_pppm;
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if (!gewaldflag) {
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double gew1,gew2,lprx,lpry,lprz,spr;
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double gew1,gew2,dgew,f,fmid,hmin,rtb;
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int ncount;
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gew1 = g_ewald + 0.01;
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gew1 = 0.0;
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g_ewald = gew1;
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f = diffpr(hx,hy,hz,q2,acons);
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hmin = MIN(hx,MIN(hy,hz));
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gew2 = 10/hmin;
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g_ewald = gew2;
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fmid = diffpr(hx,hy,hz,q2,acons);
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if (f*fmid >= 0.0) error->all("Cannot compute PPPM G");
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rtb = f < 0.0 ? (dgew=gew2-gew1,gew1) : (dgew=gew1-gew2,gew2);
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ncount = 0;
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err = LARGE;
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er1 = 0.0;
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while (fabs(err) > SMALL) {
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lprx = rms(dx,xprd,natoms,q2,acons);
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lpry = rms(dy,yprd,natoms,q2,acons);
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lprz = rms(dz,zprd_slab,natoms,q2,acons);
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lpr = sqrt(lprx*lprx + lpry*lpry + lprz*lprz) / sqrt(3.0);
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spr = 2.0*q2 * exp(-g_ewald*g_ewald*cutoff*cutoff) /
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sqrt(natoms*cutoff*xprd*yprd*zprd_slab);
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err = log(lpr) - log(spr);
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er2 = er1;
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er1 = err;
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gew2 = gew1;
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gew1 = g_ewald;
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if ((er1 - er2) == 0.0) g_ewald = gew1 + er1;
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else g_ewald = gew1 + er1*(gew2 - gew1)/(er1 - er2);
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while (fabs(dgew) > SMALL && fmid != 0.0) {
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dgew *= 0.5;
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g_ewald = rtb + dgew;
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fmid = diffpr(hx,hy,hz,q2,acons);
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if (fmid <= 0.0) rtb = g_ewald;
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ncount++;
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if (ncount > LARGE) error->all("Cannot compute PPPM G");
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}
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}
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// compute final RMS precision
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// final RMS precision
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double lprx = rms(dx,xprd,natoms,q2,acons);
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double lpry = rms(dy,yprd,natoms,q2,acons);
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double lprz = rms(dz,zprd_slab,natoms,q2,acons);
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lpr = sqrt(lprx*lprx + lpry*lpry + lprz*lprz) / sqrt(3.0);
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double lprx = rms(hx,xprd,natoms,q2,acons);
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double lpry = rms(hy,yprd,natoms,q2,acons);
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double lprz = rms(hz,zprd_slab,natoms,q2,acons);
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double lpr = sqrt(lprx*lprx + lpry*lpry + lprz*lprz) / sqrt(3.0);
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double spr = 2.0*q2 * exp(-g_ewald*g_ewald*cutoff*cutoff) /
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sqrt(natoms*cutoff*xprd*yprd*zprd_slab);
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@ -1019,6 +991,28 @@ double PPPM::rms(double h, double prd, double natoms,
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return value;
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}
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/* ----------------------------------------------------------------------
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compute difference in real-space and kspace RMS precision
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------------------------------------------------------------------------- */
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double PPPM::diffpr(double hx, double hy, double hz, double q2, double **acons)
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{
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double lprx,lpry,lprz,kspace_prec,real_prec;
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double xprd = domain->xprd;
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double yprd = domain->yprd;
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double zprd = domain->zprd;
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double natoms = atom->natoms;
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lprx = rms(hx,xprd,natoms,q2,acons);
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lpry = rms(hy,yprd,natoms,q2,acons);
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lprz = rms(hz,zprd*slab_volfactor,natoms,q2,acons);
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kspace_prec = sqrt(lprx*lprx + lpry*lpry + lprz*lprz) / sqrt(3.0);
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real_prec = 2.0*q2 * exp(-g_ewald*g_ewald*cutoff*cutoff) /
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sqrt(natoms*cutoff*xprd*yprd*zprd);
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double value = kspace_prec - real_prec;
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return value;
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}
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/* ----------------------------------------------------------------------
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denominator for Hockney-Eastwood Green's function
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of x,y,z = sin(kx*deltax/2), etc
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@ -78,6 +78,7 @@ class PPPM : public KSpace {
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void deallocate();
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int factorable(int);
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double rms(double, double, double, double, double **);
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double diffpr(double, double, double, double, double **);
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void compute_gf_denom();
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double gf_denom(double, double, double);
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virtual void particle_map();
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