LayeraLayerbNextLayerclayeraTo cubicTohexagockingCloestpalstpackingciosClosest packing of firstand second layersTilted side viewCutaway side viewof unit cellCutawaysideviewshowing face-centeredExpandedsideviewExpanded side viewshowing hexagonal unit cellcubic unit cellCubic closest packing (abcabc..) (74%)Hexagonal closest packing (abab..) (74%)配位数都是12，堆积密度都为74%
The unit cell of fcc structureThe cubic unit cell contains more than one atom.Rmi1/8atomIntheface-centredcubic(fcc)1/2atomstructure74%ofthetotalvolumeisoccupied(slightlybetterthanbccwith68%)
The unit cell of fcc structure In the face‐centred cubic (fcc) structure 74% of the total volume is occupied (slightly better than bcc with 68%)
TheunitcellofhcpstructureThehcp lattice is NOTa Bravais lattice.It can be constructedfrom a Bravais lattice with abasis containing two atoms.thepackingefficiencyisof courseexactlythesame asforthefcc structure (74 %of space occupied)
The unit cell of hcp structure
hcp不是布拉维格子！六角宝排fcc是布拉维格子！立方密排结构单元
Hexagonal Close-Packed latticea.|-a2|, with an included angle 120°[= 1.633|a [a | =|a2| =|a;|12nearestneighborsTransitionmetals :Sc.Y.Ti.Zr.Co.IA metals:Be, MgBasalPlaneHexgonal lattice + basis of 2 atoms at (0,0,0) and (2/3,1/3,1/2)