What do 1T and 2H mean in front of compounds? I have seen 1T and 2H used as prefixes for metallic compounds in literature, but I am having trouble finding what they mean. For example, 1T-HfS2 or 2H-HfS2.
These are notations that are used in identifying polytypes in layered compounds.
2H indicates 2 layers per Hexagonal unit cell (H for hexagonal).
1T indicates 1 layer per Trigonal unit cell (T for trigonal).
At least, that's my understanding.