International Tables

The electron distribution, p(r), has been computed by quantum mechanics for all neutral atoms and many ions and the values off(Q), as well as coefficients for a useful empirical approximation, are tabulated in the International Tables for Crystallography vol C [2]. In general,is a maximum equal to the nuclear charge, Z, lor Q = 0 and decreases monotonically with increasing Q. 

Because the neutron has a magnetic moment, it has a similar interaction with the clouds of impaired d or f electrons in magnetic ions and this interaction is important in studies of magnetic materials. The magnetic analogue of the atomic scattering factor is also tabulated in the International Tables [3]. Neutrons also have direct interactions with atomic nuclei, whose mass is concentrated in a volume whose radius is of the order of... 

These include rotation axes of orders two, tliree, four and six and mirror planes. They also include screM/ axes, in which a rotation operation is combined witii a translation parallel to the rotation axis in such a way that repeated application becomes a translation of the lattice, and glide planes, where a mirror reflection is combined with a translation parallel to the plane of half of a lattice translation. Each space group has a general position in which the tln-ee position coordinates, x, y and z, are independent, and most also have special positions, in which one or more coordinates are either fixed or constrained to be linear fimctions of other coordinates. The properties of the space groups are tabulated in the International Tables for Crystallography vol A [21]. 

All tenus in the sum vanish if / is odd, so (00/) reflections will be observed only if / is even. Similar restrictions apply to classes of reflections with two indices equal to zero for other types of screw axis and to classes with one index equal to zero for glide planes. These systematic absences, which are tabulated m the International Tables for Crystallography vol A, may be used to identify the space group, or at least limit die... 

Brown P J 1999 Magnetic form factors International Tables for Crystallography 2n6 edn, vol C, ed A J C Wilson and E Prince (Dordrecht Kluwer) section 4.4.5... 

Flahn Th (ed) 1992 International Tables for Crystallography vo A (Dordrecht Kluwer)... 

Wiison A J C and Prinoe E (eds) 1999 Mathematical, Physical and Chemical Tables (International Tables for Crystallography C) 2nd edn (Dordreoht Kiuwer)... 

E. W. Washburn, ed.. International Tables of theHumencal DataofPhjsics, Chemistj andTechnology (ICT), Vols. 1—7, McGiaw-HIl Book Co., Inc., New York, 1926-1930. 

British thermal unit (Btu, International Table) joule (J) 1.0550559 X 10 ... 

First international table of atomic weights (78 elements listed). 

International Tables for Crystallography, Vol. A, Space-Group Symmetry, edited by Theo Hahn, 2nd ed. (Kluwer Academic, Dordrecht, 1989). 

Mlocalorfe (International Table) kilocalorie (mean) kilocalorie (thermochemicai) kilocaiorie (thermochemicai)/min kiiocaiorie (thermochemical)/s kiiogram-fbrce (kgf) kgf-m... 

The 230 space-group types are listed in full in International Tables for Crystallography, Volume A [48], Whenever crystal symmetry is to be considered, this fundamental tabular work should be consulted. It includes figures that show the relative positions of the symmetry elements as well as details concerning all possible sites in the unit cell (cf. next section). 

The different sets of positions in crystals are called Wyckoff positions. They are listed for every space-group type in International Tables for Crystallography, Volume A, in the following way (example space-group type Nr. 87, 74/m) ... 

A two-dimensional disorder results when rod-like polymeric molecules are mutually shifted with statistical frequency. Translational symmetry then only exists in the direction of the molecules, and not in the transverse directions. The rod is a three-dimensional object with one-dimensional translational symmetry. Its symmetry is that of a rod group. Layer groups and rod groups are subperiodic groups. They are listed in detail in International Tables for Crystallography, Volume E. 

Set up the Barnighausen tree for the relation between disordered and ordered AuCu3, including the relations between the Wyckoff positions (Fig. 15.1, p. 158). You will need International Tables for Crystallography [48], Volume A, and advantageously also Volume A1 [181]. Will ordered AuCu3 form twins ... 

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