Re: [ESPResSo] magnetic dipolar binary mixtures

[Valera, Manuel]

Dear Juan,
Thanks for the reply.

So instead of 

part $p0 pos $x $y $z dip 0 0 1 dipm $factor type $type mass 1.0

I should set

part $p0 pos $x $y $z dip 0 0 $factor dipm 1.0 type $type mass 1.0

So I need to set dip and not dipm.

Thanks again

Manuel


________________________________________
From: Juan Jose Cerdà address@hidden
Sent: Monday, October 04, 2010 5:15 AM
To: Valera, Manuel
Cc: address@hidden
Subject: Re: [ESPResSo] magnetic dipolar binary mixtures

Dear Manuel,

             You must set the components of the dipolar particle, not
the modulus directly ...

              Best,
                   JJ


On 10/02/2010 06:01 AM, Valera, Manuel wrote:
> Dear users,
>
> Hello to all,
>
> I am trying to simulate a system with binary mixtures of magnetic dipolar 
> particles having dopoles mu1 and mu2
> However, setting the field dipm for the particle does not seem to have any 
> effect.
> I have attached the function add_p3m_dipolar_pair_force, the values dipm are 
> only used if NPT is enable, lines 349-354 below.
> Is this a feature? Is there a way to simulate binary dipolar systems?
> Thanks in advanced.
>
> Manuel
>
>
> 00286 MDINLINE double add_p3m_dipolar_pair_force(Particle *p1, Particle *p2,
> 00287                                            double *d,double 
> dist2,double dist,double force[3])
> 00288 {
> 00289   int j;
> 00290 #ifdef NPT
> 00291   double fac1;
> 00292 #endif
> 00293   double adist, erfc_part_ri, coeff, exp_adist2, dist2i;
> 00294   double mimj, mir, mjr;
> 00295   double B_r, C_r, D_r;
> 00296   double alpsq = p3m.Dalpha * p3m.Dalpha;
> 00297   double mixmj[3], mixr[3], mjxr[3];
> 00298
> 00299   if(dist<  p3m.Dr_cut&&  dist>  0) {
> 00300     adist = p3m.Dalpha * dist;
> 00301     #if USE_ERFC_APPROXIMATION
> 00302        erfc_part_ri = AS_erfc_part(adist) / dist;
> 00303     #else
> 00304        erfc_part_ri = erfc(adist) / dist;
> 00305     #endif
> 00306
> 00307   //Calculate scalar multiplications for vectors mi, mj, rij
> 00308   mimj = p1->r.dip[0]*p2->r.dip[0] + p1->r.dip[1]*p2->r.dip[1] + 
> p1->r.dip[2]*p2->r.dip[2];
> 00309   mir = p1->r.dip[0]*d[0] + p1->r.dip[1]*d[1] + p1->r.dip[2]*d[2];
> 00310   mjr = p2->r.dip[0]*d[0] + p2->r.dip[1]*d[1] + p2->r.dip[2]*d[2];
> 00311
> 00312   coeff = 2.0*p3m.Dalpha*wupii;
> 00313   dist2i = 1 / dist2;
> 00314   exp_adist2 = exp(-adist*adist);
> 00315
> 00316   if(p3m.Daccuracy>  5e-06)
> 00317     B_r = (erfc_part_ri + coeff) * exp_adist2 * dist2i;
> 00318   else
> 00319     B_r = (erfc(adist)/dist + coeff * exp_adist2) * dist2i;
> 00320
> 00321   C_r = (3*B_r + 2*alpsq*coeff*exp_adist2) * dist2i;
> 00322   D_r = (5*C_r + 4*coeff*alpsq*alpsq*exp_adist2) * dist2i;
> 00323
> 00324   // Calculate real-space forces
> 00325   for(j=0;j<3;j++)
> 00326     force[j] += coulomb.Dprefactor *((mimj*d[j] + p1->r.dip[j]*mjr + 
> p2->r.dip[j]*mir) * C_r - mir*mjr*D_r*d[j]) ;
> 00327
> 00328   //Calculate vector multiplications for vectors mi, mj, rij
> 00329
> 00330   mixmj[0] = p1->r.dip[1]*p2->r.dip[2] - p1->r.dip[2]*p2->r.dip[1];
> 00331   mixmj[1] = p1->r.dip[2]*p2->r.dip[0] - p1->r.dip[0]*p2->r.dip[2];
> 00332   mixmj[2] = p1->r.dip[0]*p2->r.dip[1] - p1->r.dip[1]*p2->r.dip[0];
> 00333
> 00334   mixr[0] = p1->r.dip[1]*d[2] - p1->r.dip[2]*d[1];
> 00335   mixr[1] = p1->r.dip[2]*d[0] - p1->r.dip[0]*d[2];
> 00336   mixr[2] = p1->r.dip[0]*d[1] - p1->r.dip[1]*d[0];
> 00337
> 00338   mjxr[0] = p2->r.dip[1]*d[2] - p2->r.dip[2]*d[1];
> 00339   mjxr[1] = p2->r.dip[2]*d[0] - p2->r.dip[0]*d[2];
> 00340   mjxr[2] = p2->r.dip[0]*d[1] - p2->r.dip[1]*d[0];
> 00341
> 00342   // Calculate real-space torques
> 00343 #ifdef ROTATION
> 00344   for(j=0;j<3;j++){
> 00345     p1->f.torque[j] += coulomb.Dprefactor *(-mixmj[j]*B_r + 
> mixr[j]*mjr*C_r);
> 00346     p2->f.torque[j] += coulomb.Dprefactor *( mixmj[j]*B_r + 
> mjxr[j]*mir*C_r);
> 00347   }
> 00348 #endif
> 00349 #ifdef NPT
> 00350 #if USE_ERFC_APPROXIMATION
> 00351   fac1 = coulomb.Dprefactor * p1->p.dipm*p2->p.dipm * exp(-adist*adist);
> 00352 #else
> 00353   fac1 = coulomb.Dprefactor * p1->p.dipm*p2->p.dipm;
> 00354 #endif
> 00355   return fac1 * ( mimj*B_r - mir*mjr * C_r );
> 00356 #endif
> 00357   }
> 00358   return 0.0;
> 00359 }
> 00360
> 00362 MDINLINE double p3m_dipolar_pair_energy(Particle *p1, Particle *p2,
> 00363                                       double *d,double dist2,double 
> dist)
> 00364 {
> 00365   double /* fac1,*/ adist, erfc_part_ri, coeff, exp_adist2, dist2i;
> 00366   double mimj, mir, mjr;
> 00367   double B_r, C_r;
> 00368   double alpsq = p3m.Dalpha * p3m.Dalpha;
> 00369
> 00370   if(dist<  p3m.Dr_cut&&  dist>  0) {
> 00371     adist = p3m.Dalpha * dist;
> 00372     /*fac1 = coulomb.Dprefactor;*/
> 00373
> 00374 #if USE_ERFC_APPROXIMATION
> 00375     erfc_part_ri = AS_erfc_part(adist) / dist;
> 00376     /*  fac1 = coulomb.Dprefactor * p1->p.dipm*p2->p.dipm; IT WAS WRONG 
> */ /* *exp(-adist*adist); */
> 00377 #else
> 00378     erfc_part_ri = erfc(adist) / dist;
> 00379     /* fac1 = coulomb.Dprefactor * p1->p.dipm*p2->p.dipm;  IT WAS 
> WRONG*/
> 00380 #endif
> 00381
> 00382     //Calculate scalar multiplications for vectors mi, mj, rij
> 00383     mimj = p1->r.dip[0]*p2->r.dip[0] + p1->r.dip[1]*p2->r.dip[1] + 
> p1->r.dip[2]*p2->r.dip[2];
> 00384     mir = p1->r.dip[0]*d[0] + p1->r.dip[1]*d[1] + p1->r.dip[2]*d[2];
> 00385     mjr = p2->r.dip[0]*d[0] + p2->r.dip[1]*d[1] + p2->r.dip[2]*d[2];
> 00386
> 00387     coeff = 2.0*p3m.Dalpha*wupii;
> 00388     dist2i = 1 / dist2;
> 00389     exp_adist2 = exp(-adist*adist);
> 00390
> 00391     if(p3m.Daccuracy>  5e-06)
> 00392       B_r = (erfc_part_ri + coeff) * exp_adist2 * dist2i;
> 00393     else
> 00394       B_r = (erfc(adist)/dist + coeff * exp_adist2) * dist2i;
> 00395
> 00396     C_r = (3*B_r + 2*alpsq*coeff*exp_adist2) * dist2i;
> 00397
> 00398     /*
> 00399       printf("(%4i %4i) pair energy = %f (B_r=%15.12f 
> C_r=%15.12f)\n",p1->p.identity,p2->p.identity,fac1*(mimj*B_r-mir*mjr*C_r),B_r,C_r);
> 00400     */
> 00401
> 00402     /* old line return fac1 * ( mimj*B_r - mir*mjr * C_r );*/
> 00403     return coulomb.Dprefactor * ( mimj*B_r - mir*mjr * C_r );
> 00404   }
> 00405   return 0.0;
> 00406 }
> 00407
> 00409 #endif /* of defined(MAGNETOSTATICS) */
>
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>
>


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