Page 27 - Microsoft PowerPoint - lecture1.ppt

2.1 Basics of Structures

Wyckoff-notation - example

Crystal data

Formula sum Mg SiO (Olivine)
4
2
Crystal system orthorhombic

Space group P b n m (no. 62)
Unit cell dimensions a = 4.75(2) Å, b = 10.25(4) Å, c = 6.00(2) Å

Z 4

Atomic coordinates

Atom Ox. Wyck. x y z
Mg1 +2 4a 0.00000 0.00000 0.00000

Mg2 +2 4c 0.00995(600) 0.27734(600) 0.75000

Si1 +4 4c 0.07373(500) 0.4043(50) 0.25000
O1 -2 4c 0.23242(1000) 0.0918(100) 0.75000

O2 -2 4c 0.2793(100) 0.05078(1000) 0.25000

O3 -2 8d 0.22266(1000) 0.33594(1000) 0.46289(1000)