QWalk documentation

The main components of a QMC (or just quantum!) calculation are:

  1. The Hamiltonian. This is the contents of the SYSTEM section.
  2. The Trial Wavefunction. This is the contents of the TRIALFUNC section.
  3. The Method used to evaluate properties. This is the contents of the METHOD section
  4. The Observables calculated. These are generally inserted in the METHOD section with the keyword AVERAGE.

The input of QWalk is set up to provide those four components of a calculation in a modular way. To assist with this, there are several important helper components:

  1. Simple Basis functions to represent 3-dimensional functions in real space.
  2. One-particle orbitals made up of linear combinations of basis functions.
  3. Converter programs to translate wave functions from DFT and quantum chemistry codes to QWalk format.

Input rules

  • Whitespace is not important
  • You can comment a line with '#'
  • Keywords are case-insensitive, but string arguments are case-sensitive
  • There are three types of keywords
    • flags: no argument. For example, 'TMOVES'.
    • floats, integers and strings: a single argument. For example, 'VMC_NCONFIG 20000'
    • sections: a collection of keywords denoted by curly braces { }. For example, 'METHOD { VMC NBLOCK 50 NDECORR 3 AVERAGE { SK } }'
  • The order of keywords is not important unless a keyword is repeated. For example, multiple METHOD sections in an input file will execute them in order.