Author Topic: Definitions of split valence orbitals  (Read 4699 times)

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Offline Quantamania

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Definitions of split valence orbitals
« on: August 25, 2009, 19:33 »
Fellows,
      I am continuing to work on my dissertation draft, which features a lot of calculations using this program.  Right now I am encountering some challenges from my mentor.  One of these is the definition of split valence orbitals in my theoretical calculation section of the draft. So I would like to see good illustrations of split valence orbitals.  Split valence orbitals are the basis sets we use in the program, and the type of orbital I routinely use is the double zeta double polarized basis set.  What I am looking for is a clear and concise description of split valence orbitals and how they contribute to an approximation of the Schrodinger equation solutions.  This will help me explain the basis sets I used in my calculations better, and as I am a visual learner, pictures or illustrations help me a lot.

Some questions to consider:

What is the general definition of a split valence orbital?  Why were they originally developed as an approximation to the Schrodinger equation? Based on literature I have found, it is a composite of two wavefunctions represented by their own basis sets.

What advantages do split valence orbitals offer to theoretical calculations?  Compared to Hartree-Fock orbitals, Slater basis sets (STO-3G), and popularly used Gaussian basis sets (like 6-31G, a basis set that uses six primitive orbitals plus a few Gaussian wavefunctions for each atomic orbital)?

Are there good literature sources that I can use to help with definitions of split valence orbitals?

I appreciate your help with this and hope others can learn from these questions.

Offline Anders Blom

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Re: Definitions of split valence orbitals
« Reply #1 on: August 25, 2009, 21:02 »
There are a lot of basic SIESTA references that would be relevant:

  • Phys Rev B 66, 205101 (2002)
  • physica status solidi b 215, 809 (1999)
  • J. Phys C 14, 2745 (2002)

I also found this useful, albeit as all lecture notes a bit brief: http://www.chem.wayne.edu/~hbs/chm6440/Chem6440%20basis.ppt. Actually, have a look at the other presentations too at http://www.chem.wayne.edu/~hbs/chm6440/.

I also suggest googling for some lecture notes from SIESTA summer schools, on "Introduction to the SIESTA method" and "Pseudopotential and basis generation" in particular.

Good luck writing up your thesis, it will be interesting to read it!