  Building on the success of Quantum Monte Carlo techniques such as diffusion
Monte Carlo, alternative stochastic approaches to solve electronic structure
problems have emerged over the last decade. The full configuration interaction
quantum Monte Carlo (FCIQMC) method allows one to systematically approach the
exact solution of such problems, for cases where very high accuracy is desired.
The introduction of FCIQMC has subsequently led to the development of coupled
cluster Monte Carlo (CCMC) and density matrix quantum Monte Carlo (DMQMC),
allowing stochastic sampling of the coupled cluster wave function and the exact
thermal density matrix, respectively. In this article we describe the HANDE-QMC
code, an open-source implementation of FCIQMC, CCMC and DMQMC, including
initiator and semi-stochastic adaptations. We describe our code and demonstrate
its use on three example systems; a molecule (nitric oxide), a model solid (the
uniform electron gas), and a real solid (diamond). An illustrative tutorial is
also included.
