Chemistry - How does molecular structure affect physical properties?

Predicting (approximate) physical properties starting with molecules is complicated, below. Nobody has ever produced a way to accurately predict how molecules will pack in a crystal structure. Big Pharma is desperate to predict crystal polymorphs and their properties. Slightly vast amounts of grant funding pursued predicted super-explosive octanitrocubane. When it was finally synthesized it crystallized in a less dense crystal structure than expected, deeply disappointing the DoD.

If you have a way to predict crystal structures given complex formula units, you're a big winner.