Visit the http://www.sscha.eu website to download and install the code, as well as to learn how to use it. You find the full theory and examples of applications in this paper: https://arxiv.org/abs/2103.03973 .

The stochastic self-consistent harmonic approximation (SSCHA) is a full computational python package that simulates thermodynamic and phononic properties of materials accounting for anharmonicity beyond perturbation theory, including quantum and thermal fluctuations.

If you are simulating thermal transport, thermal expansion, phase diagrams, or any phonon-related properties (as vibrational spectroscopy), then you need the SSCHA code. The method is based on a full-quantum variational method that optimizes the nuclear wave-functions (or density matrix at finite temperature) to minimize the free energy. In this way it can be used to calculate thermodynamic properties of strongly anharmonic systems and the conditions at which first- and second-order phase transitions occur, estimate the phonon frequencies expected experimentally, obtain spectral functions, phonon lifetimes, determine the structural changes imposed by quantum effects, and so on. The SSCHA software can also optimize the lattice geometry at finite temperature, enabling the calculation of thermal expansion and phase diagrams.

The SSCHA comes both as a python library and as stand-alone software, which is initialized by input files with the same syntax as Quantum ESPRESSO. It can be coupled with any ab initio engine for force and energy calculations, or it can also be used with force fields. It can interact through the Atomic Simulation Environment (ASE) and has an implemented interface for automatic submission of jobs in a remote cluster. Tutorials, FAQs, and documentation are available on the website http://www.sscha.eu, a discussion panel in which to ask questions and interact with the developers and other members of the community on the GitHub page https://github.com/SSCHAcode/python-sscha.