Atomic packing factor

This document discusses different crystal structures and their properties. It describes the body centered cubic (BCC) structure, including that there is one atom at the center of the unit cube and atoms at the corners which are shared between units. It also describes the hexagonal close-packed (HCP) structure and the arrangement of atoms. Finally, it defines and calculates the atomic packing factor for simple cubic, face centered cubic, BCC and HCP unit cells, showing HCP has the highest packing efficiency.