Hello,

I am mainly doing CASSCF calculations with MOLPRO, but I want to do the equivalent with GAUSSIAN. I think that in MOLPRO, both the ci and orbital coefficients are optimized together to minimise the ensemble energy of all the states computed.

By default, without putting the 'weight' keyword, the orbitals are optimized in a state-average scheme, meaning the energy of each state matter equally in the optimization.

In GAUSSIAN, to do state-averaged calculations, I guess I need to put the 'stateaverage' keyword, and manually set all the coefficients. But my question is what GAUSSIAN does if I don't put the keyword and the coefficients? What are their value by default?

Because if the coefficient is just 1 for a precise excited state (the nstate), and 0 for the others, how can the nstate be orthogonal to the previous one, since the orbitals will not be optimized to describe it, and its ci coefficient either, since they wouldn't matter for the optimization procedure?

I may have miss, or misunderstood something.. Anyone to highlight me on this question?