ACESIII is an electronic structure calculation program with a focus on correlated methods. It is the parallel successor to ACESII, employing the Super Instruction Assembly Language (SIAL) as parallelization framework. Features include:

Energies, analytic gradients and analytic hessians for the following methods: * Restricted/unrestricted spin or restricted open-shell Hartree-Fock (HF) * Second-order Moeller-Plesset pertubation theory (MP2)

Energies and analytic gradients for the following methods: * Coupled cluster singles and doubles (CCSD)

Additionally, it can compute energies for the following methods: * Coupled cluster singles and doubles with pertubative triples (CCSD(T)) * Quadratic configuration-interaction singles and doubles (QCISD)

Excited states can be calculated by the following methods: * Qadratic configuration interaction singles and doubles * Coupled cluster equation-of-motion (EOM-CC)

It also includes an internal coordinate geometry optimizer. If analytic gradients are not available, numerical gradients via finite differences are used.