quantum Monte Carlo Calculations

Using the JDFTx to CASINO interface

JDFTx provides an option to output wavefunctions and potentials for use in quantum Monte Carlo calculations in the CASINO code. In addition to vacuum calculations, this interface also enables solvation through the use of external potentials and second order correction energies [27].

To export orbitals, and optionally external potential from any solvation model, include the line

dump End QMC

in the input file. This command will convert the plane-wave wavefunction coefficients (and potential) to Bspline coefficients in the CASINO format. See Ref. [27] for the procedure to extract the solvation energy from the resulting QMC calculation.

Note that such calculations must use pseudopotentials appropriate for QMC (see the CASINO website), which should also be available in (or convertible to) a JDFTx-supported format (see Pseudopotentials).

Tips

• Some solvation models may behave in casino better than others, depending on the features of the potentials used: sharp features in potentials will cause numerical problems in QMC.
• For molecules, use truncated Coulomb potentials to match the behavior in CASINO