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zulqarnain

Member

Registered: 2017-11-27

Posts: 6

Basis set and functional

Hi professor
I do computational calculations, that require obviously Method and Basis set. But i wonder, what is going behind the scene during calculation.if we solve time independent Schrodinger equation, we require wave function and Hamiltonian operator to get energy (for many electron system). Basis set, by defination is used to approximate wave function. Its ok, but what's about method, does it approximate Hamiltonian operator?

Best Regards
Zulqarnain Chaughtai

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,830

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Re: Basis set and functional

For practical chemical systems, because the Hamiltonian opterator is too complicated, the Schrodinger equation can only be solved numercially and approximately, and there is no unique way to do this. Various theoretical methods such as KS-DFT, HF, CI, CC, MPn use different ideas to get approximate solution of Schrodinger equation of chemical systems. More information can be found in quantum chemistry text books, such as "Quantum Chemistry" written by Levine.