  The Wu-Wentzcovitch semi-analytical method (SAM) is a concise and predictive
formalism to calculate the high-pressure and high-temperature (high-PT)
thermoelastic tensor (Cij) of crystalline materials. This method has been
successfully applied to materials across different crystal systems in
conjunction with ab initio calculations of static elastic coefficients and
phonon frequencies. Such results have offered first-hand insights into the
composition and structure of the Earth's mantle.
  Here we introduce the cij package, a Python implementation of the SAM-Cij
formalism. It enables a thermoelasticity calculation to be initiated from a
single command and fully configurable from a calculation settings file to work
with solids within any crystalline system. These features allow SAM-Cij
calculations to work on a personal computer and to be easily integrated as a
part of high-throughput workflows. Here we show the performance of this code
for three minerals from different crystal systems at their relevant PTs:
diopside (monoclinic), akimotoite (trigonal), and bridgmanite (orthorhombic).
