### double negative imaginary frequency after dimer run

Posted:

**Tue Feb 04, 2020 4:24 am**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 remove the second -ve frequency not on rxn coordinate ? Technically, the TS structure from dimer run do look like a reasonable transition state structure for this reaction.I already tried using the max negative frequency as the input MODECAR for the next dimer run but still could not remove the second negative frequency which is not on rxn coordinate. I have used 111 kpoints and smaller ENCUT here since I was so close to convergence.

Attached is the dimer run with VASPVIB.MOLF file containing all the vibration frequencies.

Thanks

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 remove the second -ve frequency not on rxn coordinate ? Technically, the TS structure from dimer run do look like a reasonable transition state structure for this reaction.I already tried using the max negative frequency as the input MODECAR for the next dimer run but still could not remove the second negative frequency which is not on rxn coordinate. I have used 111 kpoints and smaller ENCUT here since I was so close to convergence.

Attached is the dimer run with VASPVIB.MOLF file containing all the vibration frequencies.

Thanks