I get that a harmonic picture of the potential in a material isn't enough to study lattice dynamics thoroughly. The quasi-harmonic approximation is a good workaround and helps incorporate thermal expansion effects in the lattice. I've read and heard at times that a so-and-so material is anharmoni...

Recently, I learnt that basis sets can be contracted as segmented (like def2 or 6-31G) or general (like cc-PVTZ, or ANO). The general contraction allows all the primitives to appear in all shells, whereas segmented does not do that. Most books on quantum chemistry also mention that QM programs us...