Convergence and rotational steps after CENTCAR is written
Posted: Mon Aug 09, 2021 10:33 pm
Dear all,
I am having some problems understanding the structure of a dimer calculation, in particular about the convergence criteria, when the CENTCAR is written and specially why there seem to be rotational steps after the last CENTCAR (point 4 below). In the attached example the last step only says " Dimer: Projection", previous X rotational steps appear as " Dimer: Itr 13 Rot X \n Dimer: Rotation", before that the central step is "Dimer: Itr 13 Rot 0 \n Dimer: Central Point" and before that there is another " Dimer: Projection", so my questions are:
1) When is the CENTCAR file written? in "Projection" or "Central Point"? Is there some indication in the OUTCAR of when the CENTCAR file is written?
The entries in DIMCAR correspond to "Projection steps"? Does the atomic forces ("TOTAL-FORCE (eV/Angst)" block) directly above a "Dimer: Projection" file correspond to the coordinates written in the converged CENTCAR file?
2) Other of my calculations that end up without rotations in the last steps only say "Dimer: Central Point", does it indicates the positions and atomic forces in the last "TOTAL-FORCE (eV/Angst)" block directly correspond to the CENTCAR file? CONTCAR and CENTCAR files are the same in those cases.
3) According to the webpage, the dimer converges when the FORCE in DIMCAR is below the selected EDIFFG. This is not the case in the attached example but it ended saying it reached convergence. All atomic forces in the last "TOTAL-FORCE (eV/Angst)" are below EDIFFG as if that was the criteria used to claim convergence. What is used as criteria at the end?
4) I know from this forum to always use the CENTCAR file to continue dimers or for frequencies of a converged dimmer and it worked fine for the attached transition state but something I don't understand is that the CENTCAR file was written minutes before the CONTCAR, they have different geometries. According to XDATCAR the CENTCAR was the 68th geometry and CONTCAR is the last one(74th). It seems like the last geometry written was the CONTCAR file and if this correspond to the last "Dimmer: Projection" after Iteration 13, the CONTCAR geometry and not the CENTCAR geometry would have the lower atomic (and tangential) forces. Why is that?
5) are WAVECAR and CHGCAR along with every step (with the default flags in the INCAR)? in my example where it seems there are steps after the CENTCAR file is written, the WAVECAR would not correspond to the CENTCAR. In this case the CENTCAR should not be used with the WAVECAR for a frequency calculation.
Thanks and best regards,
Sebastian.
I am having some problems understanding the structure of a dimer calculation, in particular about the convergence criteria, when the CENTCAR is written and specially why there seem to be rotational steps after the last CENTCAR (point 4 below). In the attached example the last step only says " Dimer: Projection", previous X rotational steps appear as " Dimer: Itr 13 Rot X \n Dimer: Rotation", before that the central step is "Dimer: Itr 13 Rot 0 \n Dimer: Central Point" and before that there is another " Dimer: Projection", so my questions are:
1) When is the CENTCAR file written? in "Projection" or "Central Point"? Is there some indication in the OUTCAR of when the CENTCAR file is written?
The entries in DIMCAR correspond to "Projection steps"? Does the atomic forces ("TOTAL-FORCE (eV/Angst)" block) directly above a "Dimer: Projection" file correspond to the coordinates written in the converged CENTCAR file?
2) Other of my calculations that end up without rotations in the last steps only say "Dimer: Central Point", does it indicates the positions and atomic forces in the last "TOTAL-FORCE (eV/Angst)" block directly correspond to the CENTCAR file? CONTCAR and CENTCAR files are the same in those cases.
3) According to the webpage, the dimer converges when the FORCE in DIMCAR is below the selected EDIFFG. This is not the case in the attached example but it ended saying it reached convergence. All atomic forces in the last "TOTAL-FORCE (eV/Angst)" are below EDIFFG as if that was the criteria used to claim convergence. What is used as criteria at the end?
4) I know from this forum to always use the CENTCAR file to continue dimers or for frequencies of a converged dimmer and it worked fine for the attached transition state but something I don't understand is that the CENTCAR file was written minutes before the CONTCAR, they have different geometries. According to XDATCAR the CENTCAR was the 68th geometry and CONTCAR is the last one(74th). It seems like the last geometry written was the CONTCAR file and if this correspond to the last "Dimmer: Projection" after Iteration 13, the CONTCAR geometry and not the CENTCAR geometry would have the lower atomic (and tangential) forces. Why is that?
5) are WAVECAR and CHGCAR along with every step (with the default flags in the INCAR)? in my example where it seems there are steps after the CENTCAR file is written, the WAVECAR would not correspond to the CENTCAR. In this case the CENTCAR should not be used with the WAVECAR for a frequency calculation.
Thanks and best regards,
Sebastian.