The latest release of Molpro provides a range of new functionality, including methods developed in the Manby group

## Wavefunction-in-DFT embedding

A key new addition is wavefunction-in-DFT embedding through the projector method with basis-set truncation. This enables straightforward embedding of practically any electronic structure method implemented in Molpro in a chemical environment modelled by DFT. Unlike many embedding methods of this kind

there are no issues with partitioning across covalent bonds.

We have performed many calculations using the combination CCSD(T)-in-DFT, with the expensive coupled-cluster calculation only on a few, chemically active atoms. *The exciting opportunity here is that the method all but eliminates dependence on choice of exchange-correlation functional*.

The research behind this functionality was carried out by Martina Stella, Simon Bennie and Rob Pennifold in the Manby group; and by Jason Goodpaster and Taylor Barnes in Tom Miller’s group at Caltech.

## Distinguishable cluster theory

Distinguishable cluster theory with singles and doubles (DCSD) is a simple modification of CCSD, but with remarkable properties, including the ability to dissociate molecules correctly even with a closed-shell reference state.

The method was developed by Daniel Kats while he was a DFG-funded postdoc in the Manby group. There is much discussion about what exactly this approximation means (but see Daniel’s interesting paper about a screened Coulomb derivation). Whatever it turns out to mean, DCSD is already a useful tool and a powerful addition to the set of available methods. Now in Molpro running it is as simple as replacing `ccsd` with `dcsd` in the input (and the computational cost is the same as CCSD). Gradients as well as F12, orbital-optimized and Brueckner variants are available.