ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
An expression that approximates Debye–Waller B values by a sum of three terms is derived from the theory of lattice dynamics in the harmonic approximation. For cubic crystals (Mκ is the mass of the κth atom in the unit cell): Bκ = ακ T + 2π2h2/3k TMκ + γκ/M2T3, where T ≲ ΘD/2 and ακ and γκ are constants, depending on interatomic forces only. It is shown that for temperatures above the Debye temperature ΘD of the lattice, the second and third terms in the above expression can be neglected. From this, it follows that above the Debye temperature Debye–Waller B values become independent of the atomic masses. Consequently, the heavier atoms in a lattice do not necessarily have the smaller B values.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739472000361
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