Note that anisotropy in thermal expansion is accounted for through the anisotropy of CTE denoted as α. Because we do not perform renormalization at sparse temperature points, and noting that CTE is generally not very sensitive to temperature (in other words, close to being constant), we expand the lattice by ∆L ≈ α(T )T at each temperature, and redo renormalization from the solution obtained at V = V 0 . This second renormalization process tends to converge after much fewer iterations since the initial solution would already be quite close to the true solution, except that V ̸ = V 0 by only a small difference.