UT theoretical chemistry code forum

Hey graeme

Thanks for your comments. The vibrational modes are calculated by freezing the surface atoms to save time and just check if the obtained TA state has a single imaginary frequency. I will rerun the dimer calculation as advised and keep you posted.

I will check with the linear response ...

Hey Dr. Graeme

I have been running dimer method for CO oxidation to CO2 on Pd adatom over ceria 100. However, I am getting significant double negative frequencies on vibration calculation for converged dimer TS structure. Is there anything you would suggest to further refine the dimer run and ...

Hey Graeme

I agree with the NEB/dimer at cheap settings, however sometimes the reconverging the TS state back to the original settings and higher kpoints take time (I generally use POTIM 0.05/0.1 for reconverging).
As for the high torque, I have been getting them on other systems as well. I will ...

Also found out the following warning errors through out the log files and OUTCAR files.

WARNING in EDDRMM: call to ZHEGV failed, returncode = 6 3 4 with different numbers each time during each SCF cycles. The SCF cycles still converge though even after these warnings.

Such errors have been ...

Thanks for taking time to converge the dimer. However, as I see - I need to redo a geometric optimisation with the original kpoints and original slab width to get the correct energy.

I still do not understand the origin of high torque as I described earlier, though lower kpoints and lower ENCUTs ...

Dr. Henkelman

Thanks for your reply. Yes the SCFs are converging well here. Please find attached the current run below with the input parameters. Just to tell you about the system that I am running it on :it is a PdO on ceria100 surface for CO to CO2 conversion where oxygen from one side are taken ...

Hi all

I have been running a dimer caluclation for TS state (CO to CO2 conversion on ceria 100 surface), however I have been getting consistently high torque which does not drop as the dimer rotates, as below for DROTMAX = 5 (I have tried already with DROTMAX = high values like 50):

Step Force ...

Dr. Graeme

I have been running dimer for a transition state with LBFGS optimiser, with default values other than INVCURV = 0.005 (I read in the forum, it makes the optimiser rather conservative in taking steps). However, the adsorbate molecule breaks off and drifts apart in some 200th iteration ...

OK
As then what do you suggest for re-optimisation if lower POTIM values do not work and higher POTIM takes the strucutre away from the obtained TS state ?

thanks

Dr. Graeme

As suggested by you in this forum throughout, during a dimer or NEB run approaching forces lesser than 0.1 ev, I lower the constraints on KPOINTS from original to 1 1 1 which lets the run computationally faster and I get the Transition state with this lowered KPOINTS. However, when I try ...

Hi Dr. Graeme

I have been running dimer calculation from NEB (when the forces dropped to 0.1 ev) with IOPT 3 (deafult values )and 10^-7 EDIFF.
However as found below in the DIMCAR (a part of it), the curvature turns to positive value in the 2nd dimer step and remains positive.

1 3.20328 1.19596 ...

Great Thanks

Dear Dr. Graeme

please let me know if you have any updates on this.

Thanks

[quote=sxd375 post_id=9757 time=1520453277 user_id=8521]
well Thanks

I have another question - can I use IBRION 1 (quasi newton) with low POTIM value and EDIFF 10^-5 in place of IOPT =2 that i am using here( Since IOPT 2 requires curvature calculation and EDIFF 10^-8 requires more running time on ...

Sorry to bother u again.

I continued the dimer run as posted in the beginning of this thread and I got following DIMCAR with IOPT 2 :

Step Force Torque Energy Curvature Angle
1 2.04134 1.05964 -815.09297 -2.71707 1.46944
1 2.04134 0.94002 -815.09297 -2.73440 2.58905
2 2.18434 1.52218 -815.17822 ...