How do I pick a basis set for an ab-initio Hartree-Fock evaluation ? In other words, what are the important characteristics of a basis set so that a proper choice can be made ?

  • $\begingroup$ I wonder why you are using Hartree-Fock at all. DFT is more accurate at the same computational cost so Hartree-Fock is primarily used only as the starting point for many-body calculations such as coupled-cluster. $\endgroup$ – Jeff Hammond Apr 13 '13 at 20:35

This is a pretty big topic, but the basic important qualities of an atom-centered basis set are:

  • The number of separate, unlinked functions it uses at the valence level (the so-called *zeta* count), which allow the modeling of that many different electronic environments, practically speaking.
  • Additional higher angular momentum so-called *polarisation* functions to allow for more angular complexity.
  • Whether it has diffuse functions to model more spacially extensive orbitals - so called *augmented* functions.

Generally, though, for Hartree-Fock:

  • Double-zeta for very quick, very rough structural parameters.
  • Double-zeta + polarisation for slightly less rough structural information, large systems (100+ atoms), or simple bonding environments like alkanes.
  • Triple-zeta for better accuracy and useful energies.
  • Augmented functions if you're working with anions.

Going to a better basis set than this for Hartree-Fock probably won't gain you much. In any case, unless you're moving on to a more complex method, you should probably be using density-functional theory (DFT) instead.

For more information on basis sets including how different basis sets are labelled, I recommend chapter 5.2 in Jensen's "Introduction to Computational Chemistry".


Here are some references that might be useful:


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.