Materials with solid volume greater than liquid volume Water has a solid volume greater than its liquid volume. 

This question is in two parts.

1) Are there other materials that have solid volumes greater than liquid volumes? 2) What about the structure of a molecule makes its solid volume greater than its liquid volume?
There is a bunch of such materials; among the elemental compounds, they include silicon, gallium, germanium, and bismuth. As for the properties... well, it just so happens that their crystal structure contains a little too much of empty space. Crystal packing is a tricky thing, it can't be predicted with certainty even with the most sophisticated methods.