Introduction to Density Functional Theory (90' lecture)

Ronald Cohen, Carnegie Institution of Washington

Link to Presentation slides (in PPT or PDF) format:

Topics

• What is Density Functional Theory?
  • DFT is a formally exact theory that connects ground state properties to the charge density.
  • The exact functional is unknown, but good approximations exist.
• What is DFT used for in QMC?
  • DFT is used to relax ground state structures, since QMC relaxation is not yet tractable for crystals.
  • DFT is used to compute phonons to obtain quasiharmonic estimates of zero point and thermal contributions to the free energy.
  • DFT is used to generate trial wavefunctions for QMC.
  • Sometimes DFT is used to estimate finite size corrections to QMC.
• Functionals and Functional Derivatives
• Hohenberg-Kohn Theorem
• Kohn-Sham method
• Density Functionals
  • Local Density Approximation
  • Generalized Gradient Approximation
• Basis Sets
  • Plane Waves
  • Gaussians
• Pseudopotentials

Prerequisite reading

• Ashcroft and Mermin, Solid State Physics, Chapters 1-11

Recommended reading

• Martin, Electronic Structure, Chapters 1-15
• Thijssen, Computational Physics, Second Edition, Chapters 3, 5 and 6