I can look into why you’re getting a “crash” with no further information, but two things I can say now:
- I don’t know what “interaction matrices” are. Do you mean Hamiltonian matrix elements/integrals?
- You can’t automatically determine the natural orbitals from setting up a molecular geometry and a basis set. You need to do some computation to determine the one-electron reduced density matrix and determine your natural orbitals from that. Different computations have different ways to get the density matrix back out. What method did you have in mind? (This is probably related to the crash - you haven’t computed NO occupations to return.)