We are modeling the transition state (TS) for CO₂ hydrogenation on a solid-state catalyst using a cluster with explicit solvent including an H₃O⁺ ion, under different applied potentials via VASPsol++. Our workflow was as follows:
1. Optimized initial and final states at −0.5 V vs SHE.
2. Performed a CI-NEB calculation at −0.5 V vs SHE.
3. Carried out a frequency calculation on the highest energy image, which showed an imaginary frequency corresponding to the reaction coordinate.
4. Used the Improved Dimer Method (IDM), which converged to a TS with one imaginary frequency along the reaction path.
Next, we attempted to take this optimized TS to a more negative potential. Frequency calculations still showed an imaginary frequency along the reaction path, but when we used this as a starting point for IDM, the structure “exploded” during the optimization.
Here is the INCAR we used for IDM:
ISTART = 0
ICHARG = 1
ISMEAR = 0
SIGMA = 0.2
EDIFF = 1E-06 # Tried 1E-08, same result
EDIFFG = -0.05
ALGO = Fast
NSW = 1000
IBRION = 44
POTIM = 0.05 # Tried 0.01, still exploded
ISYM = 0
LREAL = Auto # Tried LREAL = FALSE, still exploded
IVDW = 11
LSOL = .TRUE.
ISOL = 2
C_MOLAR = 1.0
R_ION = 4
EFERMI_ref = -3.57
Any advice or insights would be greatly appreciated. Thank you.
