ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Absolute values of the squares of the structure amplitudes of AlN were measured with monochromatic Cu Kα radiation in the temperature interval 85–670 °K in order to determine the mean square vibration displacements and atomic scattering factors of Al and N ions. From the F2 data, the parameter Uo/c controlling the separation of Al and N ions along the c axis was determined as 0.386 ± 0.001 compared with 0.375 for the case of the ideal structure (c/a = 1.633) and 0.380 for the case of equality of all the nearest interatomic distances (at c/a = 1.600). Temperature studies have shown that in AlN anisotropy of mean square vibration displacements (U2) occurs. Thus, U2xy = (0.30 ± 0.02) 10−2Å2, U2z = (0.65 ± 0.03)10−2Å2 for Al ion and U2xy = (0.52 ± 0.02)10−2Å2, U2z = (1.00 ± 0.03)10−2Å2 for N ion at room temperature. The coefficient of linear expansion (α) is also anisotropic. In the temperature range 298–670°K αz = (3.0 ± 0.2)10−6 deg−1 and αxy = (3.8 ± 0.2)10−6 deg−1. The values of F2exp at absolute zero are given and compared with F2theor.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739468001385
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