Density Functional Theory
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چکیده
Density functional theory in Firefly is implemented for restricted, unrestricted, and restricted-open wavefunctions. For each wavefunction, energies and analytical gradients are available. Analytical Hessians are currently not available. Instead, Hessians can be calculated in a semi-numerical fashion. Double hybrid functionals are an exception – for these functionals, only energies are currently available. Various functionals can be used, a list of these is provided in the next section. It should be noted that the DFT code in Firefly is completely different from that of GAMESS (US) with respect to both implementation and input specification.
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