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root/OpenMD/trunk/src/nonbonded/GB.cpp
Revision: 1895
Committed: Mon Jul 1 21:09:37 2013 UTC (12 years, 1 month ago) by gezelter
File size: 15715 byte(s)
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1 /*
2 * Copyright (c) 2005 The University of Notre Dame. All Rights Reserved.
3 *
4 * The University of Notre Dame grants you ("Licensee") a
5 * non-exclusive, royalty free, license to use, modify and
6 * redistribute this software in source and binary code form, provided
7 * that the following conditions are met:
8 *
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the
15 * distribution.
16 *
17 * This software is provided "AS IS," without a warranty of any
18 * kind. All express or implied conditions, representations and
19 * warranties, including any implied warranty of merchantability,
20 * fitness for a particular purpose or non-infringement, are hereby
21 * excluded. The University of Notre Dame and its licensors shall not
22 * be liable for any damages suffered by licensee as a result of
23 * using, modifying or distributing the software or its
24 * derivatives. In no event will the University of Notre Dame or its
25 * licensors be liable for any lost revenue, profit or data, or for
26 * direct, indirect, special, consequential, incidental or punitive
27 * damages, however caused and regardless of the theory of liability,
28 * arising out of the use of or inability to use software, even if the
29 * University of Notre Dame has been advised of the possibility of
30 * such damages.
31 *
32 * SUPPORT OPEN SCIENCE! If you use OpenMD or its source code in your
33 * research, please cite the appropriate papers when you publish your
34 * work. Good starting points are:
35 *
36 * [1] Meineke, et al., J. Comp. Chem. 26, 252-271 (2005).
37 * [2] Fennell & Gezelter, J. Chem. Phys. 124, 234104 (2006).
38 * [3] Sun, Lin & Gezelter, J. Chem. Phys. 128, 234107 (2008).
39 * [4] Kuang & Gezelter, J. Chem. Phys. 133, 164101 (2010).
40 * [5] Vardeman, Stocker & Gezelter, J. Chem. Theory Comput. 7, 834 (2011).
41 */
42
43 #include <stdio.h>
44 #include <string.h>
45
46 #include <cmath>
47 #include "nonbonded/GB.hpp"
48 #include "utils/simError.h"
49 #include "types/LennardJonesAdapter.hpp"
50 #include "types/GayBerneAdapter.hpp"
51
52 using namespace std;
53 namespace OpenMD {
54
55 /* GB is the Gay-Berne interaction for ellipsoidal particles. The original
56 * paper (for identical uniaxial particles) is:
57 * J. G. Gay and B. J. Berne, J. Chem. Phys., 74, 3316-3319 (1981).
58 * A more-general GB potential for dissimilar uniaxial particles:
59 * D. J. Cleaver, C. M. Care, M. P. Allen and M. P. Neal, Phys. Rev. E,
60 * 54, 559-567 (1996).
61 * Further parameterizations can be found in:
62 * A. P. J. Emerson, G. R. Luckhurst and S. G. Whatling, Mol. Phys.,
63 * 82, 113-124 (1994).
64 * And a nice force expression:
65 * G. R. Luckhurst and R. A. Stephens, Liq. Cryst. 8, 451-464 (1990).
66 * Even clearer force and torque expressions:
67 * P. A. Golubkov and P. Y. Ren, J. Chem. Phys., 125, 64103 (2006).
68 * New expressions for cross interactions of strength parameters:
69 * J. Wu, X. Zhen, H. Shen, G. Li, and P. Ren, J. Chem. Phys.,
70 * 135, 155104 (2011).
71 *
72 * In this version of the GB interaction, each uniaxial ellipsoidal type
73 * is described using a set of 6 parameters:
74 * d: range parameter for side-by-side (S) and cross (X) configurations
75 * l: range parameter for end-to-end (E) configuration
76 * epsilon_X: well-depth parameter for cross (X) configuration
77 * epsilon_S: well-depth parameter for side-by-side (S) configuration
78 * epsilon_E: well depth parameter for end-to-end (E) configuration
79 * dw: "softness" of the potential
80 *
81 * Additionally, there are two "universal" paramters to govern the overall
82 * importance of the purely orientational (nu) and the mixed
83 * orientational / translational (mu) parts of strength of the interactions.
84 * These parameters have default or "canonical" values, but may be changed
85 * as a force field option:
86 * nu_: purely orientational part : defaults to 1
87 * mu_: mixed orientational / translational part : defaults to 2
88 */
89
90
91 GB::GB() : name_("GB"), initialized_(false), mu_(2.0), nu_(1.0), forceField_(NULL) {}
92
93 void GB::initialize() {
94
95 GBtypes.clear();
96 GBtids.clear();
97 MixingMap.clear();
98 nGB_ = 0;
99
100 GBtids.resize( forceField_->getNAtomType(), -1);
101
102 ForceFieldOptions& fopts = forceField_->getForceFieldOptions();
103 mu_ = fopts.getGayBerneMu();
104 nu_ = fopts.getGayBerneNu();
105
106 // GB handles all of the GB-GB interactions as well as GB-LJ cross
107 // interactions:
108 set<AtomType*>::iterator at;
109 for (at = simTypes_.begin(); at != simTypes_.end(); ++at) {
110 if ((*at)->isGayBerne()) nGB_++;
111 if ((*at)->isLennardJones()) nGB_++;
112 }
113
114 MixingMap.resize(nGB_);
115 for (at = simTypes_.begin(); at != simTypes_.end(); ++at) {
116 if ((*at)->isGayBerne() || (*at)->isLennardJones()) addType( *at );
117 }
118
119 initialized_ = true;
120 }
121
122 void GB::addType(AtomType* atomType){
123
124 // add it to the map:
125 int atid = atomType->getIdent();
126 int gbtid = GBtypes.size();
127
128 pair<set<int>::iterator,bool> ret;
129 ret = GBtypes.insert( atid );
130 if (ret.second == false) {
131 sprintf( painCave.errMsg,
132 "GB already had a previous entry with ident %d\n",
133 atid) ;
134 painCave.severity = OPENMD_INFO;
135 painCave.isFatal = 0;
136 simError();
137 }
138
139 GBtids[atid] = gbtid;
140 MixingMap[gbtid].resize( nGB_ );
141
142 RealType d1, l1, eX1, eS1, eE1, dw1;
143
144 LennardJonesAdapter lja1 = LennardJonesAdapter(atomType);
145 GayBerneAdapter gba1 = GayBerneAdapter(atomType);
146 if (gba1.isGayBerne()) {
147 d1 = gba1.getD();
148 l1 = gba1.getL();
149 eX1 = gba1.getEpsX();
150 eS1 = gba1.getEpsS();
151 eE1 = gba1.getEpsE();
152 dw1 = gba1.getDw();
153 } else if (lja1.isLennardJones()) {
154 d1 = lja1.getSigma() / sqrt(2.0);
155 l1 = d1;
156 eX1 = lja1.getEpsilon();
157 eS1 = eX1;
158 eE1 = eX1;
159 dw1 = 1.0;
160 } else {
161 sprintf( painCave.errMsg,
162 "GB::addType was passed an atomType (%s) that does not\n"
163 "\tappear to be a Gay-Berne or Lennard-Jones atom.\n",
164 atomType->getName().c_str());
165 painCave.severity = OPENMD_ERROR;
166 painCave.isFatal = 1;
167 simError();
168 }
169
170
171 // Now, iterate over all known types and add to the mixing map:
172
173 std::set<int>::iterator it;
174 for( it = GBtypes.begin(); it != GBtypes.end(); ++it) {
175
176 int gbtid2 = GBtids[ (*it) ];
177 AtomType* atype2 = forceField_->getAtomType( (*it) );
178
179 LennardJonesAdapter lja2 = LennardJonesAdapter(atype2);
180 GayBerneAdapter gba2 = GayBerneAdapter(atype2);
181 RealType d2, l2, eX2, eS2, eE2, dw2;
182
183 if (gba2.isGayBerne()) {
184 d2 = gba2.getD();
185 l2 = gba2.getL();
186 eX2 = gba2.getEpsX();
187 eS2 = gba2.getEpsS();
188 eE2 = gba2.getEpsE();
189 dw2 = gba2.getDw();
190 } else if (lja2.isLennardJones()) {
191 d2 = lja2.getSigma() / sqrt(2.0);
192 l2 = d2;
193 eX2 = lja2.getEpsilon();
194 eS2 = eX2;
195 eE2 = eX2;
196 dw2 = 1.0;
197 } else {
198 sprintf( painCave.errMsg,
199 "GB::addType found an atomType (%s) that does not\n"
200 "\tappear to be a Gay-Berne or Lennard-Jones atom.\n",
201 atype2->getName().c_str());
202 painCave.severity = OPENMD_ERROR;
203 painCave.isFatal = 1;
204 simError();
205 }
206
207
208 GBInteractionData mixer1, mixer2;
209
210 // Cleaver paper uses sqrt of squares to get sigma0 for
211 // mixed interactions.
212
213 mixer1.sigma0 = sqrt(d1*d1 + d2*d2);
214 mixer1.xa2 = (l1*l1 - d1*d1)/(l1*l1 + d2*d2);
215 mixer1.xai2 = (l2*l2 - d2*d2)/(l2*l2 + d1*d1);
216 mixer1.x2 = (l1*l1 - d1*d1) * (l2*l2 - d2*d2) /
217 ((l2*l2 + d1*d1) * (l1*l1 + d2*d2));
218
219 mixer2.sigma0 = mixer1.sigma0;
220 // xa2 and xai2 for j-i pairs are reversed from the same i-j pairing.
221 // Swapping the particles reverses the anisotropy parameters:
222 mixer2.xa2 = mixer1.xai2;
223 mixer2.xai2 = mixer1.xa2;
224 mixer2.x2 = mixer1.x2;
225
226 // assumed LB mixing rules for now:
227
228 mixer1.dw = 0.5 * (dw1 + dw2);
229 mixer1.eps0 = sqrt(eX1 * eX2);
230
231 mixer2.dw = mixer1.dw;
232 mixer2.eps0 = mixer1.eps0;
233
234 RealType mi = RealType(1.0)/mu_;
235
236 mixer1.xpap2 = (pow(eS1, mi) - pow(eE1, mi)) / (pow(eS1, mi) + pow(eE2, mi));
237 mixer1.xpapi2 = (pow(eS2, mi) - pow(eE2, mi)) / (pow(eS2, mi) + pow(eE1, mi));
238 mixer1.xp2 = (pow(eS1, mi) - pow(eE1, mi)) * (pow(eS2, mi) - pow(eE2, mi)) /
239 (pow(eS2, mi) + pow(eE1, mi)) / (pow(eS1, mi) + pow(eE2, mi)) ;
240
241 // xpap2 and xpapi2 for j-i pairs are reversed from the same i-j pairing.
242 // Swapping the particles reverses the anisotropy parameters:
243 mixer2.xpap2 = mixer1.xpapi2;
244 mixer2.xpapi2 = mixer1.xpap2;
245 mixer2.xp2 = mixer1.xp2;
246
247 // only add this pairing if at least one of the atoms is a Gay-Berne atom
248
249 if (gba1.isGayBerne() || gba2.isGayBerne()) {
250 MixingMap[gbtid2].resize( nGB_ );
251 MixingMap[gbtid][gbtid2] = mixer1;
252 if (gbtid2 != gbtid)
253 MixingMap[gbtid2][gbtid] = mixer2;
254 }
255 }
256 }
257
258 void GB::calcForce(InteractionData &idat) {
259
260 if (!initialized_) initialize();
261
262 GBInteractionData &mixer = MixingMap[GBtids[idat.atid1]][GBtids[idat.atid2]];
263
264 RealType sigma0 = mixer.sigma0;
265 RealType dw = mixer.dw;
266 RealType eps0 = mixer.eps0;
267 RealType x2 = mixer.x2;
268 RealType xa2 = mixer.xa2;
269 RealType xai2 = mixer.xai2;
270 RealType xp2 = mixer.xp2;
271 RealType xpap2 = mixer.xpap2;
272 RealType xpapi2 = mixer.xpapi2;
273
274 // cerr << "atypes = " << idat.atypes.first->getName() << " " << idat.atypes.second->getName() << "\n";
275 // cerr << "sigma0 = " <<mixer.sigma0 <<"\n";
276 // cerr << "dw = " <<mixer.dw <<"\n";
277 // cerr << "eps0 = " <<mixer.eps0 <<"\n";
278 // cerr << "x2 = " <<mixer.x2 <<"\n";
279 // cerr << "xa2 = " <<mixer.xa2 <<"\n";
280 // cerr << "xai2 = " <<mixer.xai2 <<"\n";
281 // cerr << "xp2 = " <<mixer.xp2 <<"\n";
282 // cerr << "xpap2 = " <<mixer.xpap2 <<"\n";
283 // cerr << "xpapi2 = " <<mixer.xpapi2 <<"\n";
284
285 Vector3d ul1 = idat.A1->getRow(2);
286 Vector3d ul2 = idat.A2->getRow(2);
287
288 // cerr << "ul1 = " <<ul1<<"\n";
289 // cerr << "ul2 = " <<ul2<<"\n";
290
291 RealType a, b, g;
292
293 // This is not good. We should store this in the mixing map, and not
294 // query atom types in calc force.
295 bool i_is_LJ = idat.atypes.first->isLennardJones();
296 bool j_is_LJ = idat.atypes.second->isLennardJones();
297
298 if (i_is_LJ) {
299 a = 0.0;
300 ul1 = V3Zero;
301 } else {
302 a = dot(*(idat.d), ul1);
303 }
304
305 if (j_is_LJ) {
306 b = 0.0;
307 ul2 = V3Zero;
308 } else {
309 b = dot(*(idat.d), ul2);
310 }
311
312 if (i_is_LJ || j_is_LJ)
313 g = 0.0;
314 else
315 g = dot(ul1, ul2);
316
317 RealType au = a / *(idat.rij);
318 RealType bu = b / *(idat.rij);
319
320 RealType au2 = au * au;
321 RealType bu2 = bu * bu;
322 RealType g2 = g * g;
323
324 RealType H = (xa2 * au2 + xai2 * bu2 - 2.0*x2*au*bu*g) / (1.0 - x2*g2);
325 RealType Hp = (xpap2*au2 + xpapi2*bu2 - 2.0*xp2*au*bu*g) / (1.0 - xp2*g2);
326
327 // cerr << "au2 = " << au2 << "\n";
328 // cerr << "bu2 = " << bu2 << "\n";
329 // cerr << "g2 = " << g2 << "\n";
330 // cerr << "H = " << H << "\n";
331 // cerr << "Hp = " << Hp << "\n";
332
333 RealType sigma = sigma0 / sqrt(1.0 - H);
334 RealType e1 = 1.0 / sqrt(1.0 - x2*g2);
335 RealType e2 = 1.0 - Hp;
336 RealType eps = eps0 * pow(e1,nu_) * pow(e2,mu_);
337 RealType BigR = dw*sigma0 / (*(idat.rij) - sigma + dw*sigma0);
338
339 RealType R3 = BigR*BigR*BigR;
340 RealType R6 = R3*R3;
341 RealType R7 = R6 * BigR;
342 RealType R12 = R6*R6;
343 RealType R13 = R6*R7;
344
345 RealType U = *(idat.vdwMult) * 4.0 * eps * (R12 - R6);
346
347 RealType s3 = sigma*sigma*sigma;
348 RealType s03 = sigma0*sigma0*sigma0;
349
350 // cerr << "vdwMult = " << *(idat.vdwMult) << "\n";
351 // cerr << "eps = " << eps <<"\n";
352 // cerr << "mu = " << mu_ << "\n";
353 // cerr << "R12 = " << R12 << "\n";
354 // cerr << "R6 = " << R6 << "\n";
355 // cerr << "R13 = " << R13 << "\n";
356 // cerr << "R7 = " << R7 << "\n";
357 // cerr << "e2 = " << e2 << "\n";
358 // cerr << "rij = " << *(idat.rij) << "\n";
359 // cerr << "s3 = " << s3 << "\n";
360 // cerr << "s03 = " << s03 << "\n";
361 // cerr << "dw = " << dw << "\n";
362
363 RealType pref1 = - *(idat.vdwMult) * 8.0 * eps * mu_ * (R12 - R6) /
364 (e2 * *(idat.rij));
365
366 RealType pref2 = *(idat.vdwMult) * 8.0 * eps * s3 * (6.0*R13 - 3.0*R7) /
367 (dw* *(idat.rij) * s03);
368
369 RealType dUdr = - (pref1 * Hp + pref2 * (sigma0 * sigma0 *
370 *(idat.rij) / s3 + H));
371
372 RealType dUda = pref1 * (xpap2*au - xp2*bu*g) / (1.0 - xp2 * g2)
373 + pref2 * (xa2 * au - x2 *bu*g) / (1.0 - x2 * g2);
374
375 RealType dUdb = pref1 * (xpapi2*bu - xp2*au*g) / (1.0 - xp2 * g2)
376 + pref2 * (xai2 * bu - x2 *au*g) / (1.0 - x2 * g2);
377
378 RealType dUdg = 4.0 * eps * nu_ * (R12 - R6) * x2 * g / (1.0 - x2*g2)
379 + 8.0 * eps * mu_ * (R12 - R6) * (xp2*au*bu - Hp*xp2*g) /
380 (1.0 - xp2 * g2) / e2 + 8.0 * eps * s3 * (3.0 * R7 - 6.0 * R13) *
381 (x2 * au * bu - H * x2 * g) / (1.0 - x2 * g2) / (dw * s03);
382
383 // cerr << "pref = " << pref1 << " " << pref2 << "\n";
384 // cerr << "dU = " << dUdr << " " << dUda <<" " << dUdb << " " << dUdg << "\n";
385
386 Vector3d rhat = *(idat.d) / *(idat.rij);
387 Vector3d rxu1 = cross(*(idat.d), ul1);
388 Vector3d rxu2 = cross(*(idat.d), ul2);
389 Vector3d uxu = cross(ul1, ul2);
390
391 (*(idat.pot))[VANDERWAALS_FAMILY] += U * *(idat.sw);
392 *(idat.f1) += (dUdr * rhat + dUda * ul1 + dUdb * ul2) * *(idat.sw);
393 *(idat.t1) += (dUda * rxu1 - dUdg * uxu) * *(idat.sw);
394 *(idat.t2) += (dUdb * rxu2 + dUdg * uxu) * *(idat.sw);
395 *(idat.vpair) += U;
396
397 // cerr << "f1 term = " << (dUdr * rhat + dUda * ul1 + dUdb * ul2) * *(idat.sw) << "\n";
398 // cerr << "t1 term = " << (dUda * rxu1 - dUdg * uxu) * *(idat.sw) << "\n";
399 // cerr << "t2 term = " << (dUdb * rxu2 + dUdg * uxu) * *(idat.sw) << "\n";
400 // cerr << "vp term = " << U << "\n";
401
402 return;
403
404 }
405
406 RealType GB::getSuggestedCutoffRadius(pair<AtomType*, AtomType*> atypes) {
407 if (!initialized_) initialize();
408
409 RealType cut = 0.0;
410
411 LennardJonesAdapter lja1 = LennardJonesAdapter(atypes.first);
412 GayBerneAdapter gba1 = GayBerneAdapter(atypes.first);
413 LennardJonesAdapter lja2 = LennardJonesAdapter(atypes.second);
414 GayBerneAdapter gba2 = GayBerneAdapter(atypes.second);
415
416 if (gba1.isGayBerne()) {
417 RealType d1 = gba1.getD();
418 RealType l1 = gba1.getL();
419 // sigma is actually sqrt(2)*l for prolate ellipsoids
420 cut = max(cut, RealType(2.5) * sqrt(RealType(2.0)) * max(d1, l1));
421 } else if (lja1.isLennardJones()) {
422 cut = max(cut, RealType(2.5) * lja1.getSigma());
423 }
424
425 if (gba2.isGayBerne()) {
426 RealType d2 = gba2.getD();
427 RealType l2 = gba2.getL();
428 cut = max(cut, RealType(2.5) * sqrt(RealType(2.0)) * max(d2, l2));
429 } else if (lja2.isLennardJones()) {
430 cut = max(cut, RealType(2.5) * lja2.getSigma());
431 }
432
433 return cut;
434 }
435 }
436

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