International
Tables for
Crystallography
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 6.2, pp. 597-598

## Table 6.2.1.1

H. Lipson,a J. I. Langforda and H.-C. Hub

aSchool of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT, England, and bChina Institute of Atomic Energy, PO Box 275 (18), Beijing 102413, People's Republic of China

 Table 6.2.1.1| top | pdf | Summary of formulae for integrated powers of reflection
 Absorption is neglected in both (g) and (h).
 (a) Crystal element (b) Reflection from a crystal slab of thickness t 1. Symmetrical Bragg geometry 2. Asymmetrical Bragg geometry, when the reflecting planes are inclined at an angle to the crystal surface, and the surface normal is in the plane of the incident and reflected beams.angle of incidence and angle of emergence to the crystal surfaceDefine and : (c) Transmission from a crystal slab of thickness t 1. Symmetrical Laue geometry 2. Asymmetrical Laue geometry, when the reflecting planes are at to the crystal surface, with the normal in the plane of the incident and reflected beams.angle of incidence and angle of emergence to the normal to the crystal surfaceDefine and (d) Powder halo: no absorption correction includedwhere P is the diffracted power. (e) Debye–Scherrer lines on cylindrical film: no absorption correction includedwhere l is the length of line measured and r is the radius of the camera. Pl is the power reflected into length l. (f) Reflection from a thick block of powdered crystal of negligible transmission (g) Transmission through block of powdered crystal of thickness twhere δ′, δ are the densities of the block of powder and of the crystal in bulk, respectively. (h) Rotation photograph of small crystal, volume V 1. Beam normal to axis 2. Equi-inclination Weissenberg photograph
Symbols
Q Integrated reflection from a crystal of unit volume
Volume of crystal element
e, m Electronic charge and mass
c Speed of light
λ Wavelength of radiation
μ Linear absorption coefficient for X-rays or total attenuation coefficient for neutrons
Angle between incident and diffracted beams
In (b) and (c), as defined; in (h), latitude of reciprocal-lattice point relative to axis of rotation
V Volume of crystal, or of irradiated part of powder sample
N Number of unit cells per unit volume
ξ In (b) and (c), as defined; in (h), radial coordinate xi used in interpreting Weissenberg photographs
I0 Energy of radiation falling normally on unit area per second
hkl Indices of reflection
F Structure factor of hkl reflection
Distribution function of the mosaic blocks at angular deviation from the average reflecting plane
σ Diffraction cross section per unit volume
σ0 Diffraction cross section per unit volume at
b Asymmetry parameter
τ Reduced thickness of the crystal slab
PH/P0 Reflection power ratio, i.e. the ratio of the diffracted power to the incident power
ρ Integrated reflection power ratio from a crystal element
ρ′ Integrated reflection power ratio, angular integration of reflection power ratio
p Multiplicity factor for single-crystal methods
p′′ Multiplicity factor for powder methods