From owner-chemistry@ccl.net Fri Jun 23 09:42:00 2023 From: "Nikunj Kumar nkk749_-_gmail.com" To: CCL Subject: CCL: How to define "nroots" for CASPT2 calculations in ORCA Message-Id: <-54944-230623093848-4883-DxA/p5lukx07pOYQ8b+09A:+:server.ccl.net> X-Original-From: "Nikunj Kumar" Date: Fri, 23 Jun 2023 09:38:47 -0400 Sent to CCL by: "Nikunj Kumar" [nkk749]*[gmail.com] Dear all, I am currently engaged in a project involving an Iron system. Utilizing ORCA 5.0.3, I have conducted CASSCF calculations on a (10,10) active space, focusing on the singlet state, which have successfully attained full convergence. Now, I intend to proceed with CASPT2 calculations based on the converged wavefunction. However, I find myself uncertain about the appropriate number of "Nroots" to specify for the subsequent CASPT2 calculations. Below, I present the CAS_SCF states obtained from the preceding CASSCF calculations ROOT 0: E= -1925.4533522256 Eh 0.71174 [ 0]: 2222200000 0.15834 [ 6]: 2222020000 0.03216 [ 76]: 2220202000 0.00892 [ 116]: 2220022000 0.00886 [ 27]: 2221111000 0.00543 [ 840]: 2121201100 0.00523 [ 218]: 2211201010 0.00510 [ 791]: 2122110100 0.00447 [ 3174]: 1212211000 0.00342 [ 3186]: 1212200011 0.00329 [ 169]: 2212110010 0.00311 [ 1060]: 2112200110 0.00292 [ 3934]: 1122200101 0.00289 [ 1809]: 2022200200