Quantum Self-Consistent Ab-Initio Lattice Dynamics

The Quantum Self-Consistent Ab-Initio Lattice Dynamics package (QSCAILD) is a python library that computes temperature-dependent effective 2nd and 3rd order interatomic force constants in crystals, including anharmonic effects. QSCAILD’s approach is based on the quantum statistics of a harmonic model. The program requires the forces acting on displaced atoms of a solid as an input, which can be obtained from an external code based on density functional theory, or any other calculator. This article describes QSCAILD’s implementation, clarifies its connections to other methods, and illustrates its use in the case of the SrTiO_3 cubic perovskite structure.