Questions tagged [multi-reference]

For questions about electronic structures methods that use excitations from multiple references to model correlation. These are often prefixed with MR (e.g. MR-CC, MR-CI, MR-PT)

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4
votes
2answers
70 views

CASSCF and thermochemistry—effect of excited determinants on rotational and vibrational modes

So this question is linked to the other question I asked about the electronic patition function and CASSCF. When calculating thermochemical data (e.g. Gibbs Free energy) the partition functions are ...
4
votes
1answer
72 views

Excited determinants, electronic partition function and thermochemistry calculation

While studying statistical thermodynamics I came across the partition functions, which connect the quantum world to the macroscopic world. I understand that partition functions are used to calculate ...
10
votes
1answer
85 views

How to determine occupied and closed orbitals for a Molpro CASSCF calculation?

I am currently working with Molpro, to which I am completely new, trying to run some calculations on $\ce{PdO}$. From literature I have gathered that the ground state is given by $^3\Sigma^-$ state, ...
13
votes
1answer
91 views

What is a good practical way to determine whether or not I need to use a multiconfigurational method?

I’m planning to run a calculation of single electron transfer where my system goes from singlet to triplet biradical (presumably). So I’m wondering how to decide if I need to use milticonfigurational ...
11
votes
1answer
92 views

Is there any relation between static correlation and finite-temperature smearing?

I am new to this field, so there is a chance that I am mixing two entirely different concepts together, but it seems to be that static correlation and finite-temperature smearing in DFT are somehow ...
8
votes
0answers
57 views

What are the ways to add dynamic correlation to an MCSCF wavefunction?

We recently learned about the many types of MCSCF, which treat "static" electron correlation. There are then many ways to treat further "dynamic" electron correlation to try and ...
16
votes
3answers
185 views

What are the types of MCSCF?

Similar to: What are the types of SCF? What are the types of Quantum Monte Carlo? What are the types of ab initio Molecular Dynamics? What are the types of pseudopotentials? What are the types of DFT?...
9
votes
1answer
119 views

Can MOLPRO (2012) calculate SA-CASSCF gradients with cc-pVDZ?

I have tried to calculate state-averaged gradients with MOLPRO using the default basis set cc-pvdz. However, I was met with the error message: ...