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40 #include "long_range_correction.h"
44 #include "gromacs/ewald/ewald_utils.h"
45 #include "gromacs/math/functions.h"
46 #include "gromacs/math/units.h"
47 #include "gromacs/math/utilities.h"
48 #include "gromacs/math/vec.h"
49 #include "gromacs/mdtypes/commrec.h"
50 #include "gromacs/mdtypes/forcerec.h"
51 #include "gromacs/mdtypes/inputrec.h"
52 #include "gromacs/mdtypes/md_enums.h"
53 #include "gromacs/utility/fatalerror.h"
54 #include "gromacs/utility/gmxassert.h"
56 /* There's nothing special to do here if just masses are perturbed,
57 * but if either charge or type is perturbed then the implementation
58 * requires that B states are defined for both charge and type, and
59 * does not optimize for the cases where only one changes.
61 * The parameter vectors for B states are left undefined in atoms2md()
62 * when either FEP is inactive, or when there are no mass/charge/type
63 * perturbations. The parameter vectors for LJ-PME are likewise
64 * undefined when LJ-PME is not active. This works because
65 * bHaveChargeOrTypePerturbed handles the control flow. */
66 void ewald_LRcorrection(const int numAtomsLocal,
74 gmx_bool bHaveChargePerturbed,
83 /* We need to correct only self interactions */
84 const int start = (numAtomsLocal * thread) / numThreads;
85 const int end = (numAtomsLocal * (thread + 1)) / numThreads;
88 double Vexcl_q, dvdl_excl_q; /* Necessary for precision */
90 real Vself_q[2], Vdipole[2];
91 rvec mutot[2], dipcorrA, dipcorrB;
92 real L1_q, dipole_coeff;
93 real chargecorr[2] = { 0, 0 };
95 /* Scale the Ewald unit cell when dimension z is not periodic */
97 EwaldBoxZScaler boxScaler(ir);
98 boxScaler.scaleBox(box, scaledBox);
100 one_4pi_eps = ONE_4PI_EPS0 / fr.ic->epsilon_r;
105 L1_q = 1.0 - lambda_q;
106 /* Note that we have to transform back to gromacs units, since
107 * mu_tot contains the dipole in debye units (for output).
109 for (i = 0; (i < DIM); i++)
111 mutot[0][i] = mu_tot[0][i] * DEBYE2ENM;
112 mutot[1][i] = mu_tot[1][i] * DEBYE2ENM;
118 real boxVolume = scaledBox[XX][XX] * scaledBox[YY][YY] * scaledBox[ZZ][ZZ];
119 switch (ir.ewald_geometry)
122 if (ir.epsilon_surface != 0)
124 dipole_coeff = 2 * M_PI * ONE_4PI_EPS0
125 / ((2 * ir.epsilon_surface + fr.ic->epsilon_r) * boxVolume);
126 for (i = 0; (i < DIM); i++)
128 dipcorrA[i] = 2 * dipole_coeff * mutot[0][i];
129 dipcorrB[i] = 2 * dipole_coeff * mutot[1][i];
134 dipole_coeff = 2 * M_PI * one_4pi_eps / boxVolume;
135 dipcorrA[ZZ] = 2 * dipole_coeff * mutot[0][ZZ];
136 dipcorrB[ZZ] = 2 * dipole_coeff * mutot[1][ZZ];
137 for (int q = 0; q < (bHaveChargePerturbed ? 2 : 1); q++)
139 /* Avoid charge corrections with near-zero net charge */
140 if (fabs(fr.qsum[q]) > 1e-4)
142 chargecorr[q] = 2 * dipole_coeff * fr.qsum[q];
146 default: gmx_incons("Unsupported Ewald geometry");
150 fprintf(debug, "dipcorr = %8.3f %8.3f %8.3f\n", dipcorrA[XX], dipcorrA[YY], dipcorrA[ZZ]);
151 fprintf(debug, "mutot = %8.3f %8.3f %8.3f\n", mutot[0][XX], mutot[0][YY], mutot[0][ZZ]);
153 const bool bNeedLongRangeCorrection = (dipole_coeff != 0);
154 if (bNeedLongRangeCorrection && !bHaveChargePerturbed)
156 for (i = start; (i < end); i++)
158 for (j = 0; (j < DIM); j++)
160 f[i][j] -= dipcorrA[j] * chargeA[i];
162 if (chargecorr[0] != 0)
164 f[i][ZZ] += chargecorr[0] * chargeA[i] * x[i][ZZ];
168 else if (bNeedLongRangeCorrection)
170 for (i = start; (i < end); i++)
172 for (j = 0; (j < DIM); j++)
174 f[i][j] -= L1_q * dipcorrA[j] * chargeA[i] + lambda_q * dipcorrB[j] * chargeB[i];
176 if (chargecorr[0] != 0 || chargecorr[1] != 0)
178 f[i][ZZ] += (L1_q * chargecorr[0] * chargeA[i] + lambda_q * chargecorr[1]) * x[i][ZZ];
186 /* Global corrections only on master process */
187 if (MASTER(cr) && thread == 0)
189 for (q = 0; q < (bHaveChargePerturbed ? 2 : 1); q++)
191 /* Apply surface and charged surface dipole correction:
192 * correction = dipole_coeff * ( (dipole)^2
193 * - qsum*sum_i q_i z_i^2 - qsum^2 * box_z^2 / 12 )
195 if (dipole_coeff != 0)
197 if (ir.ewald_geometry == eewg3D)
199 Vdipole[q] = dipole_coeff * iprod(mutot[q], mutot[q]);
201 else if (ir.ewald_geometry == eewg3DC)
203 Vdipole[q] = dipole_coeff * mutot[q][ZZ] * mutot[q][ZZ];
205 if (chargecorr[q] != 0)
207 /* Here we use a non thread-parallelized loop,
208 * because this is the only loop over atoms for
209 * energies and they need reduction (unlike forces).
210 * We could implement a reduction over threads,
211 * but this case is rarely used.
213 const real* qPtr = (q == 0 ? chargeA : chargeB);
215 for (int i = 0; i < numAtomsLocal; i++)
217 sumQZ2 += qPtr[i] * x[i][ZZ] * x[i][ZZ];
219 Vdipole[q] -= dipole_coeff * fr.qsum[q]
220 * (sumQZ2 + fr.qsum[q] * box[ZZ][ZZ] * box[ZZ][ZZ] / 12);
226 if (!bHaveChargePerturbed)
228 *Vcorr_q = Vdipole[0] - Vself_q[0] - Vexcl_q;
232 *Vcorr_q = L1_q * (Vdipole[0] - Vself_q[0]) + lambda_q * (Vdipole[1] - Vself_q[1]) - Vexcl_q;
233 *dvdlambda_q += Vdipole[1] - Vself_q[1] - (Vdipole[0] - Vself_q[0]) - dvdl_excl_q;
238 fprintf(debug, "Long Range corrections for Ewald interactions:\n");
239 fprintf(debug, "q2sum = %g, Vself_q=%g\n", L1_q * fr.q2sum[0] + lambda_q * fr.q2sum[1],
240 L1_q * Vself_q[0] + lambda_q * Vself_q[1]);
241 fprintf(debug, "Electrostatic Long Range correction: Vexcl=%g\n", Vexcl_q);
242 if (MASTER(cr) && thread == 0)
244 if (ir.epsilon_surface > 0 || ir.ewald_geometry == eewg3DC)
246 fprintf(debug, "Total dipole correction: Vdipole=%g\n",
247 L1_q * Vdipole[0] + lambda_q * Vdipole[1]);