Material name Opal
Composition SiO2+nH2O (n = 3 - 10%), L-cristobalite
Chemical formula weight 60.08
System Tetragonal
Temperature (ºC) 23
a (Å), b (Å), c (Å) 4.9709(1) 4.9709(1) 6.9278(2) @
α (deg), β (deg), γ (deg) 90 90 90 @
Unit cell volume (Å3) 171.2
Calculated density (g/p3) 2.33
Z 4
Space group P41212 (No.92)
atom site g x/a y/b z/c B2)
Si 4a 1 0.3005(3) 0.3005(3) 0 1.0
O 8b 1 0.2392(3) 0.1037(2) 0.1786(2) 1.9
Comment B values were calculated on the basis of βij values in the reference.

Reference: J.J. Pluth, J.V. Smith, and J. Faber Jr., Journal of Applied Physics, 57, 1045 (1985).