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(Maybe) fixing Vdw-d3(bj) Date: 2019/09/22 01:24 Name: Jhon W. Gonzalez Dear colleagues, Even using patch 3.8.5 the vdw-d3(bj) correction results in an indefinite vdW term (Uvdw=NaN). Doing some reverse engineering, it seems that the problem is that the variable W is always less than 1.0e-12, which causes that C6 and C8 are always 0.0 and finally fdamp that is proportional to sqrt(C8/C6) becomes indeterminate, causing NaN. By modifying the following lines in Total_energy.c //if (W>1.0e-12){ C6 = Z/W; C8 = 3.0*C6*r2r4ab_dftD[wanA][wanB]; dC6ij[Gc_AN][Gc_BN]=((dZi*W)-(dWi*Z))/(W*W); /*} else{ C6 = 0.0; C8 = 0.0; dC6ij[Gc_AN][Gc_BN]=0.0; } */ For the vdw-d3(bj) correction UvdW I get values that seem to be correct, being slightly lower than with the vdw-d2 correction. The layer-layer distances for the vdw-d3(bj) correction in a bilayer system are slightly higher, with differences of less than 10% compared to the vdw-d2 case. Being aware that the error could be elsewhere. I hope that this post help to identify the problem. Best, Jhon W.

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Re: (Maybe) fixing Vdw-d3(bj) ( No.1 ) Date: 2019/10/06 09:43 Name: Kylin  <kylincaster@foxmail.com> Dear Gonzalez, I think I ever meet the similar problem for the simulation of UiO-66 crystal. The evoking of DFT-D3 gives the Nan forces for all the atoms for both "bj" and "zero" damping functions as follows. While, if I turn off the periodic (DFTD.IntDirection as 0 0 0), the simulation run smoothly. ******************************************************* MD or geometry opt. at MD = 1 ******************************************************* <Steepest_Descent> SD_scaling= 0.150011287118 <Steepest_Descent> |Maximum force| (Hartree/Bohr) = 0.000000000000 <Steepest_Descent> Criterion (Hartree/Bohr) = 0.000300000000 atom= 1, XYZ(ang) Fxyz(a.u.)= 10.3695 6.0212 7.8627 -nan -nan -nan atom= 2, XYZ(ang) Fxyz(a.u.)= 10.3525 7.7512 6.2011 -nan -nan -nan atom= 3, XYZ(ang) Fxyz(a.u.)= 10.3833 2.9109 4.6566 -nan -nan -nan atom= 4, XYZ(ang) Fxyz(a.u.)= 10.3656 4.7021 2.9325 -nan -nan -nan atom= 5, XYZ(ang) Fxyz(a.u.)= 12.4845 1.9944 8.5528 -nan -nan -nan atom= 6, XYZ(ang) Fxyz(a.u.)= 8.5531 2.0201 12.4885 -nan -nan -nan atom= 7, XYZ(ang) Fxyz(a.u.)= 7.7172 10.5339 6.2719 -nan -nan -nan atom= 8, XYZ(ang) Fxyz(a.u.)= 5.8448 10.5304 7.8186 -nan -nan -nan Thus, I has to adopt DFT-D2 in my current crystal simulation. The following is my script. Can anyone provide any suggestions about it. here is my script: https://drive.google.com/open?id=1Hi2UrL6ZcTcewlPmpSWloVRaaZg8aYKL Cheers, Kylin Re: (Maybe) fixing Vdw-d3(bj) ( No.2 ) Date: 2019/10/07 02:13 Name: Jhon W. Gonzalez Hey Kylin, Although I'm not an OpenMx developer, I think the safest option is to select the D2 approach. You can try the modification I propose (under your own risk) and compare the results. Best, Jhon Re: (Maybe) fixing Vdw-d3(bj) ( No.3 ) Date: 2019/10/16 13:41 Name: T. Ozaki Hi Jhon, Thank you for your valuable post. In fact, that part is a program bug. I will fix it in the next release of OpenMX. Best regards, TO

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