Apart from the elements, do we know of materials that are denser? I.e. can an alloy be denser than the sum of its compounds, for example if the new lattice packs denser than each of the compounds it's made from? My curiosity was spurred from rumors of a material called ultradense deuterium (not confirmed to exist), that apparently packs something like 140kg/cm^3.
closed as too broad by Carl Witthoft, Kyle Kanos, John Rennie, CuriousOne, user36790 Apr 12 '16 at 14:24
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