# Shared Flashcard Set

## Details

Crystaline Structures
Crystaline Structures
12
Mechanical Engineering
05/07/2014

Term
 Cubic Axial lengths and angles
Definition
 a=b=c, alpha=beta=gamma=90 degrees
Term
 Tetragonal Axial lengths and angles
Definition
 a=b not=c, alpha=beta=gamma=90 degrees
Term
 Orthorhombic Axial lengths and angles
Definition
 a NE b NE c, alpha=beta=gamma=90 degrees
Term
 Rhombohedral Axial lengths and angles
Definition
 a=b=c, alpha=beta=gamma NE 90 degrees
Term
 Hexagonal Axial lengths and angles
Definition
 a=b NE c, alpha=beta=90 degrees, gamma=120 degrees
Term
 Monoclinic Axial lengths and angles
Definition
 a NE b NE c, alpha=gamma=90 degrees NE beta
Term
 Triclinic Axial lengths and angles
Definition
 a NE b NE c, alpha NE beta NE gamma NE 90 degrees
Term
 Three crystal structures of most elemental metals at room temperature
Definition
 Body-centered cubic (bcc)Face-centered cubic (fcc)Hexagonal close packed (hcp)
Term
 Atomic packing factor (APF)equation
Definition
 Fraction of the unit cell volume occupied by the atomsAPF=N(atoms)V(atoms)/V(crystal)
Term
 Body-centered cubic (bcc)
Definition
 One atom at the center of the unit cellOne-eighth atom at each cornerTwo atoms in each bcc unit cellBcc metals: -Fe, V, Cr, Mo, WUnit cell face lenght a=4r/sqrt(3)
Term
 Face-centered cubic (fcc)
Definition
 One-half atom in the center of each faceOne-eight atom at each cornerFour atoms in each fcc unit cellFcc metals: -Fe, Al, Ni, Cu, Ag, Pt, Aua=4r/sqrt(2)
Term
 Hexagonal close packed (hcp)
Definition
 Based on hexagonal Bavais latticeTwo atoms associated with Bravais lattice pointOne atom centered within the unit cell, various fraction atoms at corners (four 1/6, four 1/12 atoms)Total of 2 atoms in unit cellAPF=0.74Hcp material: Be, Mg, -Ti, Zn, Zr
Supporting users have an ad free experience!