Lattice anharmonicity and thermal properties of strongly correlated Fe$_{1-x}$Co$_x$Si alloys

The temperature dependences of the thermal and elastic properties of strongly correlated metal alloys Fe$_{1-x}$Co$_x$Si ($x$ = 0.1, 0.3, 0.5) with different atomic chiralities have been calculated in the framework of the self-consistent thermodynamic model taking into account the influence of lattice anharmonicity. The lattice contributions to the heat capacity and thermal expansion coefficient of the alloys have been determined using the experimental data. It has been demonstrated that the invar effect in the thermal expansion of the lattice observed in the magnetically ordered region of Fe$_{0.7}$Co$_{0.3}$Si and Fe$_{0.5}$Co$_{0.5}$Si is not related to the lattice anharmonicity, even though its appearance correlates with variations in the atomic chirality.