Site position Wyckoff letter

Multiplicity, Wyckoff letter, site symmetry, and coordinates given for each set of equivalent positions. 

Using the International Tables for Crystallography describe every atom in terms of the multiplicities and Wyckoff letters of their site positions and establish the content of the unit cell, the simplest chemical formula and the number of formula units (Z) per unit cell. 

Multiplicity Wyckoff letter Site symmetry Coordinates of equivalent positions... 

Wyckoff letters, as described in Chapter 3 for the plane groups, label the different site symmetries that can be occupied by an atom in a unit cell. When the position chosen for the atom,... 

If an atom is placed in the unit cell of a crystal at a position, or site, (jc, y, z), identical copies of the atom must, by operation of the symmetry elements present, lie at other sites, (jq, yu zi), (x2, y2, z2) and so on. A Wyckoff letter is a site label, and each different type of site in the unit cell is given a different Wyckoff letter. 

The Wyckoff symbol is a short designation it consists of a numeral followed by a letter, for example 8/. The cipher 8 states the multiplicity, that is, the number of symmetry-equivalent points in the unit cell. The / is an alphabetical label (a, b,c,...) according to the sequence of the listing of the positions a is always the position with the highest site symmetry. 

For this group there are 11 different Wyckoff positions denoted by letters from a to k. The number of crystallographic orbit points in the primitive unit cell (multiplicity) equals np/Uq where np = 16 is the order of the point group and Uq is the order of the site symmetry group Gg. The number of points in a Wyckoff position and their coordinates are given in the International Tables with respect to the conventional unit cell of the lattice (for the space group D j with a simple Bravais lattice, the... 

The first two columns of the table contain the labels of the induced reps in the q-basis (these labels number the rows of the table) the international symbols (Roman letters a, b, c and so on) of the Wyckoff positions (sites in direct space) and the Mulliken symbols of the irrep>s of the site-symmetry groups for these Wyckoff positions. For example, d a2u) and d(e ) are the labels of induced reps in q-basis for space... 

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