Multiwfn forum

ethan

Member

Registered: 2020-02-28

Posts: 1

triplet state wfn obtained from Molcas through Molden2aim

I am wondering if there is a way to combine alpha and beta occupations and exponents using Multiwfn from a triplet state wfn file generated by Molden2aim. The molden orbitals are obtained from a CASSCF calculation in the triplet state.

When you generate the triplet wfn from a CASSCF calculation using Gaussian, the alpha and beta occupations are combined. So the problem might be Molcas because the output orbitals are always split into alpha and beta.

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 2,030

Website

Re: triplet state wfn obtained from Molcas through Molden2aim

I am not quite familiar with CASSCF calculation of Molcas, I suggest you ask developer of Molden2aim code about this question, his E-mail: zouwl[at]nwu.edu.cn

jxzou

Member

Registered: 2023-09-11

Posts: 8

Re: triplet state wfn obtained from Molcas through Molden2aim

The thing you are talking about is not "to combine alpha and beta occupations and exponents". It is probably related to two different kinds of natural orbitals: 1) spatial natural orbitals; 2) natural spin orbitals.

If you perform a ground state triplet CASSCF calculation, OpenMolcas will generate two .molden files, one is xxx.rasscf.molden and the other one is xxx.rasscf.molden.1. The spatial natural orbitals are stored in the former file, and the natural spin orbitals are stored in the latter file (which corresponds to what you called "always split into alpha and beta"). So, what you need is in xxx.rasscf.molden, and you can run

molden2fch xxx.rasscf.molden -molcas

to generate file the xxx.rasscf.fch, which can be opened and visualized by GaussView/Multiwfn. Here `molden2fch` is a utility in the open source package MOKIT.

But if you perform a triplet CASSCF calculation with multiple triple states, xxx.rasscf.molden contains the CASSCF average pseudo-natural orbitals which are often useless since they are not NOs of any electronic state. In this case, one needs to add densities in xxx.rasscf.molden.N to obtain the total density for state N, then generate NOs for this state.

Last edited by jxzou (2025-07-17 11:42:16)