Questions tagged [casscf]

For questions about performing Complete Active Space Self Consistent Field calculations

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9
votes
1answer
62 views

Which molecules have multi-reference character?

I'm using WebMO to construct molecules that have high multireference character, but I cannot seem to find any, or perhaps I'm not building them correctly on WebMO; I know singlet biradicals generally ...
7
votes
3answers
301 views

Open source FCI solvers for exact diagonalization of the many-electron Hamiltonian

What open source solvers (according to the generally accepted Open Source Definition i.e. licensed under a valid open source license) are available for full configuration interaction calculations? ...
7
votes
1answer
55 views

Frequency error in Gaussian CASSCF(10,10)

I am stuck in calculating the frequencies of one optimised geometry for naphthalene CASSCF(10,10) with Gaussian 16. I have optimised its geometry and checked the active space is the pi system of it, ...
5
votes
1answer
97 views

Modify ORCA orbitals for CASSCF

I have run a HF calculation on naphthalene and I have checked the MOs that have been obtained. Now, I have to select my active and inactive orbitals for CASCF(10,10). As there are 34 occupied orbitals,...
8
votes
1answer
128 views

Molecular orbitals and active space

During the same minute as asking this question, I also asked this at Quantum Computing SE. In Qiskit, each qubit corresponds to one spin orbital. For example, the $\ce{N2}$ molecule would have 10 ...
4
votes
0answers
48 views

Calculating wave-function overlap in MOLPRO

Is it possible to somehow calculate the inner product (or overlap) between the electronic wave-functions of excited states in Molpro? What I want to do is to compare the electronic wave-functions that ...
5
votes
1answer
65 views

In Molpro, how to calculate the orbital angular momentum?

I wish to calculate the values of the orbital angular momentum of excited electronic states, using Molpro. So $\langle L_x \rangle$, $\langle L_y \rangle$, and $\langle L_z \rangle$. (Specifically for ...
9
votes
2answers
162 views

How does MOLPRO choose active orbitals in a CASSCF calculation?

I am trying to calculate electronically excited states for the CO molecule, with the aug-cc-pVTZ basis set, and a CASSCF calculation. The documentation describes ...
4
votes
2answers
85 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
93 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
147 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, ...
8
votes
0answers
97 views

How to classify ionic and covalent excited-states?

In spectroscopy it is common to describe excited-states as ionic or covalent. I understand the concept on a toy model e.g. $\ce{H2}$ with a minimal basis set \begin{align} \Phi_0 &= [\chi_A(1) + \...
14
votes
0answers
122 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 ...
17
votes
3answers
222 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
144 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: ...
30
votes
9answers
807 views

Is there a free package with robust CASSCF functionality?

Among free software packages, which one has robust CASSCF functionality? The FCI solver can be implemented in either way, e.g., direct solver, DMRG, etc.