[oksanah]

The two polymorphs of Titanium, α-polymorph (hcp) and the β-polymorph (bcc). Which one has a greater density?

I was thinking that it is the β-polymorph (bcc), because bcc has a lower coordination number? Is this right?

[renge ishyo]

I think the higher the coordination number the higher the packing density within a given volume. Since each titanium "sphere" weighs the same, this would mean that the one with the higher coordination number would be more dense (did a quick check and found this table which would tend to back this up: http://books.google.com/books?id=68mQLz7yJ8UC&pg=PA5&lpg=PA5&dq=density+titanium+hcp+bcc&source=bl&ots=lerKelcTiT&sig=yvFM6iKFbHLH3z3f-geIeIJO5l0&hl=en&ei=3bWFS6mVMpi6tgP82eiYCQ&sa=X&oi=book_result&ct=result&resnum=2&ved=0CAgQ6AEwATgK#v=onepage&q=density%20titanium%20hcp%20bcc&f=false).