- #1

- 8

- 0

(unfilled states) in the basis set improve accuracy? What is missing in the model which is accounted for by inclusion of suc h virtual states. My guess is the the born-oppenheimer approximation but not sure??

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- Thread starter raman
- Start date

- #1

- 8

- 0

(unfilled states) in the basis set improve accuracy? What is missing in the model which is accounted for by inclusion of suc h virtual states. My guess is the the born-oppenheimer approximation but not sure??

- #2

- 41

- 0

The Born-Oppenheimer approximation has nothing to do with CI. It allows one to decouple nuclear motion from that of the electrons. This leads to a simple 1/r description of nuclear-electron attractions.

Since you've asked several questions on this topic, I suggest you have a look at: "Modern Quantum Chemistry" by A. Szabo and N.S. Ostlund.

-Jim

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