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42 #include "gromacs/legacyheaders/coulomb.h"
43 #include "gromacs/legacyheaders/macros.h"
44 #include "gromacs/legacyheaders/names.h"
45 #include "gromacs/legacyheaders/txtdump.h"
46 #include "gromacs/legacyheaders/typedefs.h"
47 #include "gromacs/legacyheaders/types/commrec.h"
48 #include "gromacs/math/units.h"
49 #include "gromacs/math/utilities.h"
50 #include "gromacs/math/vec.h"
51 #include "gromacs/utility/futil.h"
52 #include "gromacs/utility/smalloc.h"
54 real calc_ewaldcoeff_q(real rc, real dtol)
56 real x = 5, low, high;
65 while (gmx_erfc(x*rc) > dtol);
67 n = i+60; /* search tolerance is 2^-60 */
70 for (i = 0; i < n; i++)
73 if (gmx_erfc(x*rc) > dtol)
85 static real ewald_function_lj(real x, real rc)
87 real xrc, xrc2, xrc4, factor;
92 factor = exp(-xrc2)*(1 + xrc2 + xrc4/2.0);
94 factor = expf(-xrc2)*(1 + xrc2 + xrc4/2.0);
100 real calc_ewaldcoeff_lj(real rc, real dtol)
102 real x = 5, low, high;
110 while (ewald_function_lj(x, rc) > dtol);
112 n = i + 60; /* search tolerance is 2^-60 */
115 for (i = 0; i < n; ++i)
117 x = (low + high) / 2.0;
118 if (ewald_function_lj(x, rc) > dtol)
130 void ewald_LRcorrection(int start, int end,
131 t_commrec *cr, int thread, t_forcerec *fr,
132 real *chargeA, real *chargeB,
133 real *C6A, real *C6B,
134 real *sigmaA, real *sigmaB,
135 real *sigma3A, real *sigma3B,
136 gmx_bool calc_excl_corr,
137 t_blocka *excl, rvec x[],
138 matrix box, rvec mu_tot[],
139 int ewald_geometry, real epsilon_surface,
140 rvec *f, tensor vir_q, tensor vir_lj,
141 real *Vcorr_q, real *Vcorr_lj,
142 real lambda_q, real lambda_lj,
143 real *dvdlambda_q, real *dvdlambda_lj)
145 int i, i1, i2, j, k, m, iv, jv, q;
147 double Vexcl_q, dvdl_excl_q, dvdl_excl_lj; /* Necessary for precision */
150 real v, vc, qiA, qiB, dr2, rinv, enercorr;
151 real Vself_q[2], Vself_lj[2], Vdipole[2], rinv2, ewc_q = fr->ewaldcoeff_q, ewcdr;
152 real ewc_lj = fr->ewaldcoeff_lj, ewc_lj2 = ewc_lj * ewc_lj;
153 real c6Ai = 0, c6Bi = 0, c6A = 0, c6B = 0, ewcdr2, ewcdr4, c6L = 0, rinv6;
154 rvec df, dx, mutot[2], dipcorrA, dipcorrB;
155 tensor dxdf_q, dxdf_lj;
156 real vol = box[XX][XX]*box[YY][YY]*box[ZZ][ZZ];
157 real L1_q, L1_lj, dipole_coeff, qqA, qqB, qqL, vr0_q, vr0_lj = 0;
158 gmx_bool bFreeEnergy = (chargeB != NULL);
159 gmx_bool bMolPBC = fr->bMolPBC;
160 gmx_bool bDoingLBRule = (fr->ljpme_combination_rule == eljpmeLB);
162 /* This routine can be made faster by using tables instead of analytical interactions
163 * However, that requires a thorough verification that they are correct in all cases.
166 one_4pi_eps = ONE_4PI_EPS0/fr->epsilon_r;
167 vr0_q = ewc_q*M_2_SQRTPI;
168 if (EVDW_PME(fr->vdwtype))
170 vr0_lj = -pow(ewc_lj, 6)/6.0;
181 L1_lj = 1.0-lambda_lj;
182 /* Note that we have to transform back to gromacs units, since
183 * mu_tot contains the dipole in debye units (for output).
185 for (i = 0; (i < DIM); i++)
187 mutot[0][i] = mu_tot[0][i]*DEBYE2ENM;
188 mutot[1][i] = mu_tot[1][i]*DEBYE2ENM;
193 switch (ewald_geometry)
196 if (epsilon_surface != 0)
199 2*M_PI*ONE_4PI_EPS0/((2*epsilon_surface + fr->epsilon_r)*vol);
200 for (i = 0; (i < DIM); i++)
202 dipcorrA[i] = 2*dipole_coeff*mutot[0][i];
203 dipcorrB[i] = 2*dipole_coeff*mutot[1][i];
208 dipole_coeff = 2*M_PI*one_4pi_eps/vol;
209 dipcorrA[ZZ] = 2*dipole_coeff*mutot[0][ZZ];
210 dipcorrB[ZZ] = 2*dipole_coeff*mutot[1][ZZ];
213 gmx_incons("Unsupported Ewald geometry");
218 fprintf(debug, "dipcorr = %8.3f %8.3f %8.3f\n",
219 dipcorrA[XX], dipcorrA[YY], dipcorrA[ZZ]);
220 fprintf(debug, "mutot = %8.3f %8.3f %8.3f\n",
221 mutot[0][XX], mutot[0][YY], mutot[0][ZZ]);
224 if (EVDW_PME(fr->vdwtype))
228 if ((calc_excl_corr || dipole_coeff != 0) && !bFreeEnergy)
230 for (i = start; (i < end); i++)
232 /* Initiate local variables (for this i-particle) to 0 */
233 qiA = chargeA[i]*one_4pi_eps;
234 if (EVDW_PME(fr->vdwtype))
245 i2 = excl->index[i+1];
247 /* Loop over excluded neighbours */
248 for (j = i1; (j < i2); j++)
252 * First we must test whether k <> i, and then,
253 * because the exclusions are all listed twice i->k
254 * and k->i we must select just one of the two. As
255 * a minor optimization we only compute forces when
256 * the charges are non-zero.
260 qqA = qiA*chargeA[k];
261 if (EVDW_PME(fr->vdwtype))
266 c6A *= pow(0.5*(sigmaA[i]+sigmaA[k]), 6)*sigma3A[k];
269 if (qqA != 0.0 || c6A != 0.0)
274 rvec_sub(x[i], x[k], dx);
277 /* Cheap pbc_dx, assume excluded pairs are at short distance. */
278 for (m = DIM-1; (m >= 0); m--)
280 if (dx[m] > 0.5*box[m][m])
282 rvec_dec(dx, box[m]);
284 else if (dx[m] < -0.5*box[m][m])
286 rvec_inc(dx, box[m]);
291 /* Distance between two excluded particles
292 * may be zero in the case of shells
296 rinv = gmx_invsqrt(dr2);
304 vc = qqA*gmx_erf(ewcdr)*rinv;
307 /* Relative accuracy at R_ERF_R_INACC of 3e-10 */
308 #define R_ERF_R_INACC 0.006
310 /* Relative accuracy at R_ERF_R_INACC of 2e-5 */
311 #define R_ERF_R_INACC 0.1
313 /* fscal is the scalar force pre-multiplied by rinv,
314 * to normalise the relative position vector dx */
315 if (ewcdr > R_ERF_R_INACC)
317 fscal = rinv2*(vc - qqA*ewc_q*M_2_SQRTPI*exp(-ewcdr*ewcdr));
321 /* Use a fourth order series expansion for small ewcdr */
322 fscal = ewc_q*ewc_q*qqA*vr0_q*(2.0/3.0 - 0.4*ewcdr*ewcdr);
325 /* The force vector is obtained by multiplication with
326 * the relative position vector
328 svmul(fscal, dx, df);
331 for (iv = 0; (iv < DIM); iv++)
333 for (jv = 0; (jv < DIM); jv++)
335 dxdf_q[iv][jv] += dx[iv]*df[jv];
342 rinv6 = rinv2*rinv2*rinv2;
343 ewcdr2 = ewc_lj2*dr2;
344 ewcdr4 = ewcdr2*ewcdr2;
345 /* We get the excluded long-range contribution from -C6*(1-g(r))
346 * g(r) is also defined in the manual under LJ-PME
348 vc = -c6A*rinv6*(1.0 - exp(-ewcdr2)*(1 + ewcdr2 + 0.5*ewcdr4));
350 /* The force is the derivative of the potential vc.
351 * fscal is the scalar force pre-multiplied by rinv,
352 * to normalise the relative position vector dx */
353 fscal = 6.0*vc*rinv2 + c6A*rinv6*exp(-ewcdr2)*ewc_lj2*ewcdr4;
355 /* The force vector is obtained by multiplication with
356 * the relative position vector
358 svmul(fscal, dx, df);
361 for (iv = 0; (iv < DIM); iv++)
363 for (jv = 0; (jv < DIM); jv++)
365 dxdf_lj[iv][jv] += dx[iv]*df[jv];
372 Vexcl_q += qqA*vr0_q;
373 Vexcl_lj += c6A*vr0_lj;
379 /* Dipole correction on force */
380 if (dipole_coeff != 0)
382 for (j = 0; (j < DIM); j++)
384 f[i][j] -= dipcorrA[j]*chargeA[i];
389 else if (calc_excl_corr || dipole_coeff != 0)
391 for (i = start; (i < end); i++)
393 /* Initiate local variables (for this i-particle) to 0 */
394 qiA = chargeA[i]*one_4pi_eps;
395 qiB = chargeB[i]*one_4pi_eps;
396 if (EVDW_PME(fr->vdwtype))
409 i2 = excl->index[i+1];
411 /* Loop over excluded neighbours */
412 for (j = i1; (j < i2); j++)
417 qqA = qiA*chargeA[k];
418 qqB = qiB*chargeB[k];
419 if (EVDW_PME(fr->vdwtype))
425 c6A *= pow(0.5*(sigmaA[i]+sigmaA[k]), 6)*sigma3A[k];
426 c6B *= pow(0.5*(sigmaB[i]+sigmaB[k]), 6)*sigma3B[k];
429 if (qqA != 0.0 || qqB != 0.0 || c6A != 0.0 || c6B != 0.0)
434 qqL = L1_q*qqA + lambda_q*qqB;
435 if (EVDW_PME(fr->vdwtype))
437 c6L = L1_lj*c6A + lambda_lj*c6B;
439 rvec_sub(x[i], x[k], dx);
442 /* Cheap pbc_dx, assume excluded pairs are at short distance. */
443 for (m = DIM-1; (m >= 0); m--)
445 if (dx[m] > 0.5*box[m][m])
447 rvec_dec(dx, box[m]);
449 else if (dx[m] < -0.5*box[m][m])
451 rvec_inc(dx, box[m]);
458 rinv = gmx_invsqrt(dr2);
460 if (qqA != 0.0 || qqB != 0.0)
465 v = gmx_erf(ewc_q*dr)*rinv;
468 /* fscal is the scalar force pre-multiplied by rinv,
469 * to normalise the relative position vector dx */
470 fscal = rinv2*(vc-qqL*ewc_q*M_2_SQRTPI*exp(-ewc_q*ewc_q*dr2));
471 dvdl_excl_q += (qqB - qqA)*v;
473 /* The force vector is obtained by multiplication with
474 * the relative position vector
476 svmul(fscal, dx, df);
479 for (iv = 0; (iv < DIM); iv++)
481 for (jv = 0; (jv < DIM); jv++)
483 dxdf_q[iv][jv] += dx[iv]*df[jv];
488 if ((c6A != 0.0 || c6B != 0.0) && EVDW_PME(fr->vdwtype))
490 rinv6 = rinv2*rinv2*rinv2;
491 ewcdr2 = ewc_lj2*dr2;
492 ewcdr4 = ewcdr2*ewcdr2;
493 v = -rinv6*(1.0 - exp(-ewcdr2)*(1 + ewcdr2 + 0.5*ewcdr4));
496 /* fscal is the scalar force pre-multiplied by rinv,
497 * to normalise the relative position vector dx */
498 fscal = 6.0*vc*rinv2 + c6L*rinv6*exp(-ewcdr2)*ewc_lj2*ewcdr4;
499 dvdl_excl_lj += (c6B - c6A)*v;
501 /* The force vector is obtained by multiplication with
502 * the relative position vector
504 svmul(fscal, dx, df);
507 for (iv = 0; (iv < DIM); iv++)
509 for (jv = 0; (jv < DIM); jv++)
511 dxdf_lj[iv][jv] += dx[iv]*df[jv];
518 Vexcl_q += qqL*vr0_q;
519 dvdl_excl_q += (qqB - qqA)*vr0_q;
520 Vexcl_lj += c6L*vr0_lj;
521 dvdl_excl_lj += (c6B - c6A)*vr0_lj;
527 /* Dipole correction on force */
528 if (dipole_coeff != 0)
530 for (j = 0; (j < DIM); j++)
532 f[i][j] -= L1_q*dipcorrA[j]*chargeA[i]
533 + lambda_q*dipcorrB[j]*chargeB[i];
538 for (iv = 0; (iv < DIM); iv++)
540 for (jv = 0; (jv < DIM); jv++)
542 vir_q[iv][jv] += 0.5*dxdf_q[iv][jv];
543 vir_lj[iv][jv] += 0.5*dxdf_lj[iv][jv];
552 /* Global corrections only on master process */
553 if (MASTER(cr) && thread == 0)
555 for (q = 0; q < (bFreeEnergy ? 2 : 1); q++)
559 /* Self-energy correction */
560 Vself_q[q] = ewc_q*one_4pi_eps*fr->q2sum[q]*M_1_SQRTPI;
561 if (EVDW_PME(fr->vdwtype))
563 Vself_lj[q] = fr->c6sum[q]*0.5*vr0_lj;
567 /* Apply surface dipole correction:
568 * correction = dipole_coeff * (dipole)^2
570 if (dipole_coeff != 0)
572 if (ewald_geometry == eewg3D)
574 Vdipole[q] = dipole_coeff*iprod(mutot[q], mutot[q]);
576 else if (ewald_geometry == eewg3DC)
578 Vdipole[q] = dipole_coeff*mutot[q][ZZ]*mutot[q][ZZ];
585 *Vcorr_q = Vdipole[0] - Vself_q[0] - Vexcl_q;
586 if (EVDW_PME(fr->vdwtype))
588 *Vcorr_lj = -Vself_lj[0] - Vexcl_lj;
593 *Vcorr_q = L1_q*(Vdipole[0] - Vself_q[0])
594 + lambda_q*(Vdipole[1] - Vself_q[1])
596 *dvdlambda_q += Vdipole[1] - Vself_q[1]
597 - (Vdipole[0] - Vself_q[0]) - dvdl_excl_q;
598 if (EVDW_PME(fr->vdwtype))
600 *Vcorr_lj = -(L1_lj*Vself_lj[0] + lambda_lj*Vself_lj[1]) - Vexcl_lj;
601 *dvdlambda_lj += -Vself_lj[1] + Vself_lj[0] - dvdl_excl_lj;
607 fprintf(debug, "Long Range corrections for Ewald interactions:\n");
608 fprintf(debug, "start=%d,natoms=%d\n", start, end-start);
609 fprintf(debug, "q2sum = %g, Vself_q=%g c6sum = %g, Vself_lj=%g\n",
610 L1_q*fr->q2sum[0]+lambda_q*fr->q2sum[1], L1_q*Vself_q[0]+lambda_q*Vself_q[1], L1_lj*fr->c6sum[0]+lambda_lj*fr->c6sum[1], L1_lj*Vself_lj[0]+lambda_lj*Vself_lj[1]);
611 fprintf(debug, "Electrostatic Long Range correction: Vexcl=%g\n", Vexcl_q);
612 fprintf(debug, "Lennard-Jones Long Range correction: Vexcl=%g\n", Vexcl_lj);
613 if (MASTER(cr) && thread == 0)
615 if (epsilon_surface > 0 || ewald_geometry == eewg3DC)
617 fprintf(debug, "Total dipole correction: Vdipole=%g\n",
618 L1_q*Vdipole[0]+lambda_q*Vdipole[1]);
624 real ewald_charge_correction(t_commrec *cr, t_forcerec *fr, real lambda,
626 real *dvdlambda, tensor vir)
629 real vol, fac, qs2A, qs2B, vc, enercorr;
634 /* Apply charge correction */
635 vol = box[XX][XX]*box[YY][YY]*box[ZZ][ZZ];
637 fac = M_PI*ONE_4PI_EPS0/(fr->epsilon_r*2.0*vol*vol*sqr(fr->ewaldcoeff_q));
639 qs2A = fr->qsum[0]*fr->qsum[0];
640 qs2B = fr->qsum[1]*fr->qsum[1];
642 vc = (qs2A*(1 - lambda) + qs2B*lambda)*fac;
646 *dvdlambda += -vol*(qs2B - qs2A)*fac;
648 for (d = 0; d < DIM; d++)
655 fprintf(debug, "Total charge correction: Vcharge=%g\n", enercorr);