Software Available

Iterated Stockholder Atoms

Iterated stockholder atoms have recently been designed in our group and shown to compare favourably with the best alternative methods for dividing molecular charge densities into atomic pieces.

We have in-house code for producing and analysing ISAs. Please contact me for more information.


SIMPER, the Systematic Intermolecular Potential Extrapolation Routine, is a suite of programs written with EPSRC funding to calculate intermolecular potential energy surfaces for small molecules (<=2 non-H atoms each).

The strategy used is to perform an MP2 supermolecule calculation, divide it into different components using perturbation theory, and attempt to improve the electrostatic, dispersion and exchange-repulsion components by improving the treatment of intramolecular correlation to about CCSD level. This has proven to give intermolecular potentials reliably to the CCSD(T) supermolecule level of theory, at a small fraction of the cost.

The program currently has the following capabilities:

July 2009: In addition to the calculations below, density functional theory energies and properties are now available with a large number of different functionals.

Supermolecule calculations at SCF, MP2, CCSD and CCSD(T) level.

Components of the SCF and MP2 supermolecule energies.

Charge densities at SCF, MP2 and CCSD level.

Polarizabilities at UHF, CHF, MP2 and CCSD level.

Dispersion energy coefficients (time-dependent polarizabilities at imaginary frequency) at UHF, CHF, MP2 and CCSD level.

All the above can be done for restricted closed-shell or fully spin-unrestricted open-shell systems (apart from open-shell CCSD(T)).

The program is under development and, although it works, some parts are not very efficient!

In the fairly near future I hope to introduce higher-level properties and energy components.

Contact me for more details.