Hexagonal unit-cell volume
= Hexagonal unit-cell volume
{title2=$V_{\rm cell}=\sqrt3a^2c/2$}
For basal vectors of equal length $a$ separated by120degrees and perpendicular height $c$, cell volume is $a^2c\sin120^\circ=\sqrt3a^2c/2$. A full hexagonal prism drawn around it has three times this volume and must contain three times as many atoms if used for density calculations.