Skip to main content
40 votes

Is there a free package with robust CASSCF functionality?

OpenMOLCAS I'm surprised that the other two answers were given without yet any mention of OpenMOLCAS yet! There is a recent paper[1] about it for which I happen to be one of the many co-authors. ...
Nike Dattani - No Free Time's user avatar
29 votes

Is there a free package with robust CASSCF functionality?

ORCA ORCA (forum). It is fully featured, efficient, and free for academics. The input is straightforward: ...
schneiderfelipe's user avatar
18 votes

Is there a free package with robust CASSCF functionality?

PySCF Personally I would use pyscf, its not the most efficient or user friendly but it's free.
Raz Jugovic's user avatar
16 votes

Is there a free package with robust CASSCF functionality?

NWChem NWChem is a commonly use quantum chemistry software package with CASSCF included. NWChem is free, as in both free coffee and free speech. It is under ECL-2.0. It is written in FORTRAN (in case ...
Y. Zhai's user avatar
  • 1,124
14 votes

Is there a free package with robust CASSCF functionality?

BAGEL The code is available through GitHub[1] and has been described in WIRES.[2] The main advantages of BAGEL is that it has better memory and parallelization than MOLPRO. For example, MOLPRO (not ...
Cody Aldaz's user avatar
  • 8,017
11 votes
Accepted

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

The MOLPRO 2012.1 manual is no longer online, although there is an archive of at least some of the pages and you can try your luck for finding the pages you want on the archive, but it might not be ...
Nike Dattani - No Free Time's user avatar
10 votes
Accepted

Molecular orbitals and active space

As you said above, nitrogen has 2 s orbitals and one p orbital. However, one would typically freeze the chemically inactive 1s orbital, leaving you 5 electrons in 4 orbitals per atom, or 10 electrons ...
Susi Lehtola's user avatar
  • 19.8k
10 votes
Accepted

What are the types of MCSCF?

LASSCF: Localized Active Space SCF An approximation to or generalization of (depending on how you look at it) CASSCF. In CASSCF, the wave function consists of an antisymmetrized product of two factors ...
Matthew R Hermes's user avatar
8 votes

Is there a free package with robust CASSCF functionality?

Columbus Columbus is an alternative package for CASSCF and other multireference methods. There is a free and open-source distribution. It is a bit old fashioned but still widely used. Newest Reference ...
Felix's user avatar
  • 1,431
7 votes
Accepted

Modify ORCA orbitals for CASSCF

You can use the "rotate" keyword in the SCF block, like %scf rotate {30,27,90} (38,41,90} {39,48,90} end end The "90"s mean "90 degrees&...
wzkchem5's user avatar
  • 9,710
7 votes

What are the types of MCSCF?

RASSCF: Restricted Active Space SCF In a Complete Active Space (CAS) calculation, one chooses a set of occupied/virtual orbitals (the active space) from an initial Slater determinant and forms ...
Tyberius's user avatar
  • 15.6k
7 votes

Choosing an active space for CASSCF using Molpro

As a developer of MOKIT, I would like to recommend the automatic CASSCF computation using the automr utility in MOKIT. We do not need to manually choose/permute ...
jxzou's user avatar
  • 806
6 votes

Choosing an active space for CASSCF using Molpro

First of all, your syntax isn't exactly the way the MOLPRO manual for the CASSCF program (called "Multi") instructs: OCC,n1,n2,…,n8; CLOSED,n1,n2,…,n8 ...
Nike Dattani - No Free Time's user avatar
6 votes

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

MRCC One of my favorite FCI programs is the one in MRCC, because it has a few advantages over the MOLPRO FCI program (which uses the program you described in your answer). When the entire calculation ...
Nike Dattani - No Free Time's user avatar
6 votes

Is there a free package with robust CASSCF functionality?

Psi4 Psi4 (https://psicode.org/) is another open-source alternative (LGPL). I haven't used it myself but it supports CASSCF.
leopold.talirz's user avatar
6 votes

Is there a free package with robust CASSCF functionality?

GAMESS GAMESS (https://www.msg.chem.iastate.edu/GAMESS/) has an MCSCF module, which can perform CASSCF. For generating configurations it can use determinants, or configuration state functions (CSFs). ...
S R Maiti's user avatar
  • 7,131
5 votes

Is there a free package with robust CASSCF functionality?

DALTON For what I know also the Dalton suite is able to run CASSCF. It's also an open source software. You can find the tutorial to run CASSCF calculation here.
NickZ's user avatar
  • 1,509
5 votes

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

LUCIA / LUCITA Jeppe Olsen's LUCIA / LUCITA code has been included in e.g. Dalton, which is nowadays open source. The code has been successfully used in calculations including over one billion ...
Susi Lehtola's user avatar
  • 19.8k
5 votes

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

FCI Peter Knowles' FCI program, published in Computer Physics Communications, 54, 75 (1989), is available at https://bitbucket.org/pjknowles/fci/src/master/ The code is Fortran 77 and can handle at ...
Susi Lehtola's user avatar
  • 19.8k
5 votes
Accepted

How many electrons and orbitals should I include in a CASSCF calculation?

"Is there a way to get the right number of electrons and number of orbitals to use in CASSCF from just knowing what atoms or diatomic species are involved?" The "right" number of ...
Nike Dattani - No Free Time's user avatar
4 votes

Which molecules have multi-reference character?

The following small- to medium-sized molecular have multi-reference character, meaning that your CISD calculation will likely show the reference wavefunction to have a weight that is quite a fair bit ...
Nike Dattani - No Free Time's user avatar
4 votes
Accepted

Excited determinants, electronic partition function and thermochemistry calculation

"This works for organic molecules, but what happens when the excited states are closer in energy to the ground state, for example in open-shell molecules or in atoms?" If there's excited ...
Nike Dattani - No Free Time's user avatar
4 votes
Accepted

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

The occupied orbital pattern of 13 7 6 2 that you got from your Hartree-Fock calculation is not unique. For example, I've just run an RHF calculation on PdO with ...
Nike Dattani - No Free Time's user avatar
3 votes
Accepted

In Molpro, how to calculate the orbital angular momentum?

"However they are listed with parity -1, and: "Expectation values are only nonzero for symmetric operators (parity=1)"." This matches the ...
Nike Dattani - No Free Time's user avatar
3 votes

How does MOLPRO choose active orbitals in a CASSCF calculation?

You fixed the occupation within symmetries by the command "occ,6,3,3,2" and asked the program to make CASSCF for the lowest 5 singlet states of symmetry 1 ...
TKorona's user avatar
  • 39
3 votes
Accepted

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

So what happens when the contribution of excited determinants are included in the vibrational and rotational terms? Nothing, except that the Hessian and/or gradient are more difficult to evaluate, ...
Cody Aldaz's user avatar
  • 8,017
3 votes

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

I can comment on externally corrected coupled-cluster (ec-CC) methods, as I have some direct experience in this topic. Externally Corrected CC Externally corrected CC methods seek to improve the ...
Karthik Gururangan's user avatar
3 votes

Frequency error in Gaussian CASSCF(10,10)

This is not quite an answer yet, but I wanted to collect some things I found. Since it looked like this was some kind of overflow error, I tried to see if shrinking the calculation or increasing the ...
Tyberius's user avatar
  • 15.6k
3 votes

How to choose the number of roots in a CASSCF calculation?

The term "roots" refers to the number of "electronic states". If you are only interested in the ground state, then you are seeking 1 root. If you want the ground state and the ...
Nike Dattani - No Free Time's user avatar
2 votes

Table of Largest CI Components in PySCF CASSCF Calculation

You have 4 electrons in 4 spatial orbitals. Number the orbitals 0, 1, 2, and 3. Look at the lowest root. It is an open shell singlet. The spatial orbital 0 is doubly occupied, and then you have (12-21)...
Susi Lehtola's user avatar
  • 19.8k

Only top scored, non community-wiki answers of a minimum length are eligible