Issues while dealing with higher active space in CASSCF calculation

[Komal Yadav]

Dear All,

I am working on a project in which I have to carry out a (16,16) CASSCF single point calculation on an optimized geometry of a molecule. Since the molecule has C1 symmetry so we get a huge number of variables during CASSCF calculation. The normal 'determinant' driven method shows an error :

SINGULARITY IN SCHMIDT ORTHOGONALISER

However when we move to 'CSF (Configuration State Function)' method, it takes a lot of time.

Is there any way to sort out this issue in comparitively less amount of time? 

Thanking You

[Tibor Győri]

If I recall correctly, a (16,16) CASSCF is quite big, possibly pushing the limits of what is reasonably possible with any traditional algorithm. Maybe looking into the direction of DMRG and similar advanced algorithms would be a good idea.