Calculating TS on psi4

Hello all. I’ve been having trouble converging my transition state structures on psi4 using mp2 level of theory.

My input code looks like this:

memory 3 gb

molecule TS {
0 2

geometry input here


set {
reference uhf
guess sad
opt_type ts
g_convergence gau_tight
scf_type df
basis cc-pvtz
df_basis_scf cc-pvtz-jkfit
df_basis_mp2 cc-pvtz-ri
freeze_core true
dynamic_level 3


I’m dealing with a radical transition state structure that has been optimised using gaussian at ub3lyp/6-31g* level previously so I’m pretty sure it should not be a bad starting geometry.

Is there any way you guys can help me with this?

Thanks so much!

TS optimizations are notoriously tricky, without more detail of the system I’m not quite sure we can help. Perhaps @Rollin_King can say more.

Without more information (e.g., is a single-reference wavefunction reasonable here? are the forces small? have you tried computing the force constants prior to the optimization?) I can’t help.

The TS optimization code in Psi4 is not very sophisticated (PRFO steps) so you will need to begin the calculation in a region with the correct (or nearly correct) topology. Some amount of trial and error is likely.