QMCPACK is an open-source, high-performance electronic structure code that
implements numerous Quantum Monte Carlo algorithms. Its main applications are
electronic structure calculations of molecular, periodic 2D and periodic 3D
solid-state systems. Variational Monte Carlo (VMC), diffusion Monte Carlo (DMC)
and a number of other advanced QMC algorithms are implemented.

By directly solving the Schrodinger equation, QMC methods offer greater accuracy
than methods such as density functional theory, but at a trade-off of much
greater computational expense. Distinct from many other correlated many-body
methods, QMC methods are readily applicable to both bulk (periodic) and isolated
molecular systems.

WWW: https://www.qmcpack.org/