G4CMP is a framework designed to add to the Geant4 toolkit for use in condensed matter and low-energy physics. Developed for the low-temperature community, G4CMP is capable of modeling several physics processes relevant to phonon and charge collection at cryogenic temperatures. These include anisotropic phonon transport and focusing, phonon isotope scattering, anharmonic downconversion, oblique charge carrier propagation with inter-valley scattering, and emission of Neganov-Trofimov-Luke phonons by accelerated carriers. 

The package provides a collection of particle types, physics processes, and supporting utilities for this purpose. It has been used by collaborators at the SuperCDMS project to successfully reproduce theoretical predictions and experimental observations such as phonon caustics, heat pulse propagation times, and mean carrier drift velocities; the G4CMP package, however, is sufficiently general that it is useful for other experiments employing cryogenic phonon and/or ionization detectors.