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38.6 Relativistic corrections

Relativistic corrections may be calculated within the Cowan-Griffin approach
by computing expectation values of the mass-velocity and 1-electron Darwin
integrals; these should be generated using the property integral program with
keyword `REL`
The expectation values can be computed within the SCF, MCSCF and CI programs
in the usual way using the `EXPECT` command,
again with the keyword `REL`. The mass-velocity and Darwin terms, and
their sum are subsequently available through the MOLPRO variables
`MASSV`, `DARW` and `EREL` respectively.

**Subsections**

molpro@molpro.net 2019-01-19