[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From: |
Xiao Jia <xiaoj@...1508...> |

Date: |
Tue, 19 Dec 2017 16:36:20 -0500 |

Dear Dr. Kohlmeyer,

Sorry for the missing information.

I am using the latest stable version of lammps, 11Aug2017.

I tried another case with **Morse potential**, which generates consistent potential value to the log file.

While for EAM potential, it does not.

I am not sure how to quickly reproduce the simulation, because I do the modification in the cpp code.

This is how I did in the code.

I put this code segments within the end_of_step part in fix_ttm_mod.cpp and output the summation of all the potential energy as potential_all[0],

which is used for comparison with the log file.

int i, j, ii, jj, inum, jnum, itype, jtype;

double xtmp, ytmp, ztmp, delx, dely, delz, evdwl, fpair;

double rsq, eng, r, dr, dexp, factor_coul, factor_lj;

int *ilist, *jlist, *numneigh, **firstneigh;

double vir[3];

double xtmp, ytmp, ztmp, delx, dely, delz, evdwl, fpair;

double rsq, eng, r, dr, dexp, factor_coul, factor_lj;

int *ilist, *jlist, *numneigh, **firstneigh;

double vir[3];

double *special_coul = force->special_coul;

double *special_lj = force->special_lj;

int newton_pair = force->newton_pair;

inum = force->pair->list->inum;

ilist = force->pair->list->ilist;

numneigh = force->pair->list->numneigh;

firstneigh = force->pair->list->firstneigh;

ilist = force->pair->list->ilist;

numneigh = force->pair->list->numneigh;

firstneigh = force->pair->list->firstneigh;

potential_single[0] = 0.0;

potential_all[0] = 0.0;

potential_all[0] = 0.0;

for (ii = 0; ii < inum; ii++)

{

i = ilist[ii];

xtmp = x[i][0];

ytmp = x[i][1];

ztmp = x[i][2];

itype = type[i];

jlist = firstneigh[i];

jnum = numneigh[i];

{

i = ilist[ii];

xtmp = x[i][0];

ytmp = x[i][1];

ztmp = x[i][2];

itype = type[i];

jlist = firstneigh[i];

jnum = numneigh[i];

for (jj = 0; jj < jnum; jj++)

{

j = jlist[jj];

factor_lj = special_lj[sbmask(j)];

factor_coul = special_coul[sbmask(j)];

j &= NEIGHMASK;

{

j = jlist[jj];

factor_lj = special_lj[sbmask(j)];

factor_coul = special_coul[sbmask(j)];

j &= NEIGHMASK;

delx = xtmp - x[j][0];

dely = ytmp - x[j][1];

delz = ztmp - x[j][2];

rsq = delx*delx + dely*dely + delz*delz;

jtype = type[j];

dely = ytmp - x[j][1];

delz = ztmp - x[j][2];

rsq = delx*delx + dely*dely + delz*delz;

jtype = type[j];

if (rsq < cutsq[itype][jtype])

{

{

eng = pair->single(i, j, itype, jtype, rsq, factor_coul, factor_lj, fpair);

potential_single[0] += eng;

}

}

}

}

}

MPI_Allreduce(&potential_single[0], &potential_all[0], 1, MPI_DOUBLE, MPI_SUM, world);

I am not sure why different results can be generated for different potential, Morse and EAM,

and is there any difference to refer the same function single() by using different potentials.

Thanks!

On Tue, Dec 19, 2017 at 9:45 AM, Axel Kohlmeyer <akohlmey@...24...> wrote:

On Tue, Dec 19, 2017 at 3:33 AM, Xiao Jia <xiaoj@...1508...> wrote:Dear LAMMPS users,I am referring the functionsingle ()defined in pair.cpp to calculate the pairwise force coefficientfpairand thepotential energy.eng=pair->single (i, j, itype, jtype, rsq, factor_coul, factor_lj, fpair);The current potential I am using is EAM potential.The weird observation I have is that my summation of the potential energy (eng value of each pair) from all the pairs does not match with the output from log file. The value I get is -21936114 and the value from log file is -63005273, the difference is close to 3 times.The calculation of pressure based on fpair seems to be consistent with the value from log file, but the difference in potential energy is hard to understand.your e-mail is missing two important pieces of information.1) which LAMMPS version you are using exactly. what you are reporting sounds a lot like a bug that was fixed not so long ago.2) an example input deck that allows to quickly reproduce your issue (in case this is a real bug and still exists with the latest patch release).axel.I will appreciate it so much if anyone can give me any idea about this issue.Thanks!

------------------------------------------------------------ ------------------

Check out the vibrant tech community on one of the world's most

engaging tech sites, Slashdot.org! http://sdm.link/slashdot

_______________________________________________

lammps-users mailing list

lammps-users@...655....net

https://lists.sourceforge.net/lists/listinfo/lammps-users

--Dr. Axel Kohlmeyer akohlmey@...24... http://goo.gl/1wk0

College of Science & Technology, Temple University, Philadelphia PA, USA

International Centre for Theoretical Physics, Trieste. Italy.

**Follow-Ups**:**Re: [lammps-users] Different potential energy calculation results***From:*Axel Kohlmeyer <akohlmey@...24...>

**References**:**[lammps-users] Different potential energy calculation results***From:*Xiao Jia <xiaoj@...1508...>

**Re: [lammps-users] Different potential energy calculation results***From:*Axel Kohlmeyer <akohlmey@...24...>

- Prev by Date:
**Re: [lammps-users] bond swap within a single chain** - Next by Date:
**[lammps-users] relaxation system** - Previous by thread:
**Re: [lammps-users] Different potential energy calculation results** - Next by thread:
**Re: [lammps-users] Different potential energy calculation results** - Index(es):