Finite Temperature DFT

Dear Psi4 Developers,

Could you add an option for doing finite temperature DFT?

I find that there already exists an option for allowing fractional occupation number (FON) to accelerate SCF, so it should be handy to extend it to finite temperature DFT by allowing FON for the converged wavefunction.

Specifically, the FONs with Fermi-Dirac distribution smearing Gaussian smearing are most commonly used.

Reference: Springborg, Michael, R. C. Albers, and Karla Schmidt. “Fractional occupancies and temperature in electronic-structure calculations.” Physical Review B 57, no. 3 (1998): 1427.

Could you move this exact text to the Psi4 GitHub repo ( Other developers can take a peak at this there.

Moved to gibhub repo issues.