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**Gemma G****Member**- Registered: 2016-12-01
- Posts: 1

Hi all,

I want to do a caspt2 and then rassi calculation combining two sets of roots optimised in different casscf runs, these correspond to the 4^T_1 and 4^T_2 states of a Co(II) ion. Currently I am doing caspt2 calculations on each set of roots individually and then a rassi calculation from the two resulting .JobMix files with the following input file:

```
&RASSI
EJOB
NROF jobiphs
2 3 3
1 2 3
4 5 6
SpinOrbit
EPRG
1.0
MEES
```

The .JobMix files are read in correctly, and the energies from the caspt2 calculations are seen on the diagonals of the Hamiltonian for the original states. I am then running into a problem because the roots are being assumed to be orthogonal despite having a non-zero overlap. This leads to drastically changed Spin-Free energies and nonsensical states (see below). Are there any keywords or ways to get around this?

Thank you,

Gemma

```
HAMILTONIAN MATRIX FOR THE ORIGINAL STATES:
(Assumed diagonal using JOBIPH energies)
-2837.86704527
0.00000000 -2837.86481020
0.00000000 0.00000000 -2837.86139599
0.00000000 0.00000000 0.00000000 -2837.83575186
0.00000000 0.00000000 0.00000000 0.00000000 -2837.82957255
0.00000000 0.00000000 0.00000000 0.00000000 0.00000000
-2837.82546832
OVERLAP MATRIX FOR THE ORIGINAL STATES:
1.00000000
0.00000000 1.00000000
0.00000000 0.00000000 1.00000000
-0.00060728 -0.00305127 0.00095613 1.00000000
0.00625043 0.00013073 -0.00035782 0.00000000 1.00000000
0.00287249 0.00242324 0.00410730 0.00000000 -0.00000000
1.00000000
Total energies (spin-free):
:: RASSI State 1 Total energy: -2858.75240105
:: RASSI State 2 Total energy: -2849.93624070
:: RASSI State 3 Total energy: -2846.54204049
:: RASSI State 4 Total energy: -2829.20980661
:: RASSI State 5 Total energy: -2825.85646599
:: RASSI State 6 Total energy: -2817.24570093
```

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**Ignacio****Administrator**- From: Uppsala
- Registered: 2015-11-03
- Posts: 506

Maybe you want to use the HEff keyword instead?

HEFF

A spin-free effective Hamiltonian is read from JOBIPH instead of being computed. It must have been computed by an earlier program. Presently, this is done by a multi-state calculation using CASPT2. In the future, other programs may add dynamic correlation estimates in a similar way.

In contrast, EJob says explicitly that the Hamiltonian "is assumed to be diagonal".

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**daishudaishu****Member**- Registered: 2019-02-24
- Posts: 16

Is this problem fixed? I met the same problem with my calculation.

https://cobalt.itc.univie.ac.at/molcasf … php?id=451

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