Table 2. Summary of the technical parameters used for the geometry optimizations and phonon calculations on the studied ice polymorphs.

	k-point sampling
Phase	Optimization	Phonon	Supercell expansion	No. of supercell molecules
Ih	3 × 3 × 2	2 × 2 × 1	2 × 2 × 2	96
II	2 × 2 × 2	1 × 1 × 1	2 × 2 × 2	96
XV	2 × 2 × 3	1 × 1 × 2	2 × 2 × 2	80