Abstract

Anomalous thermal expansion is treated through an analytical approach, based on the anharmonic behavior of lattice vibrations of the solids CuCl and CuBr of which complete ir spectroscopic data were available for the low temperature region. In the two cases examined here, anomalous thermal expansion as well as change of anharmonic factor, as a function of temperature, show a mirrorlike proportionality. In addition, drastic changes of ir energy absorption take place within the temperature region of re-expansion, suggesting a substantial increase of the ionic fraction of binding, coupled with a corresponding decrease of the covalent fraction, within the re-expansion period. These striking events appear to be the basic reason for the re-expansion phenomenon, since the sum value of the ionic radii of the compounds in question is greater than the sum value of the covalent radii, thus enlarging the interatomic distance, instead of contracting it.

© 1972 Optical Society of America

Thermal Expansion Measurements on Four Optical Materials from Room Temperature to 10 K

James Steve Browder and Stanley S. Ballard
Appl. Opt. 11(4) 841-843 (1972)

Damping of Lattice Vibrations in Solids

J. N. Plendl
Appl. Opt. 10(1) 87-97 (1971)

Apparatus for Measuring the Thermal Expansion of Optical Materials from 30°C to 250°C

John F. Ebersole, Stanley S. Ballard, and James Steve Browder
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Theory of Thermal Imaging Using Infrared to Visible Image Up-Conversion

K. F. Hulme and J. Warner
Appl. Opt. 11(12) 2956-2964 (1972)

Far Infrared Study of the Copper Halides at Low Temperatures

J. N. Plendl, A. Hadni, J. Claudel, Y. Henninger, G. Morlot, P. Strimer, and L. C. Mansur
Appl. Opt. 5(3) 397-401 (1966)