# Interface to DKH by A. Wolf, M. Reiher, and B. A. Hess

Code author: Justin M. Turney

Section author: Justin M. Turney

Module: Keywords, DKH

## Input

For all electron calculations one can use the Douglas-Kroll-Hess (DKH) Hamiltonian to take into account scalar relativistic effects.

Minimal input for DKH single-point computation looks like this:

    molecule {
    Mg
    }

    set basis aug-cc-pvdz-dk
    set relativistic dkh

    energy('scf')

By default a 2nd-order DKH calculation is performed. To change the default order use the DKH_ORDER option. The version of the code found in Psi4 is capable of up to 4th-order DKH calculations.

## Reference

When using this code please make reference to the appropriate following paper:

- “The Generalized Douglas-Kroll Transformation,” A. Wolf, M. Reiher, and B. A. Hess, J. Chem. Phys. 117, 9215 (2002). (doi: 10.1063/1.1515314)