Cc4s - a high-performance coupled-cluster simulation code for solids and surfaces

We present the open-source ab initio simulation software Cc4s. The target applications of Cc4s are highly accurate electronic structure theory calculations of solids and surfaces using the quantum chemical coupled-cluster ansatz. The high computational cost of the CCSD(T) calculations can be overcome using the state-of-the-art high-performance tensor library CTF, allowing for efficient calculations on tens to hundreds of compute nodes. Our code interfaces with the VASP package for the calculations of the Hartree-Fock reference and related quantities.

Cc4s can perform canonical CCSD(T) calculations with more than 200 electrons. This allows for the calculation of, for example, adsorption energies of molecules on surfaces or defect properties. We will present a range of applications and discuss techniques to correct for finite size and basis set incompleteness errors.