def _set_thermal_expansion(self):
        beta = [0.0]
        for i in range(1, self._num_elems - 1):
            dt = self._temperatures[i + 1] - self._temperatures[i - 1]
            dv = self._equiv_volumes[i + 1] - self._equiv_volumes[i - 1]
            beta.append(dv / dt / self._equiv_volumes[i])

        self._thermal_expansions = beta