Lattice Constants and Thermal Expansivities of Silicon and of Calcium Fluoride between 6° and 322°K

Abstract

An x-ray back-reflection, rotating-camera technique has been used to obtain lattice constants and thermal expansivities of single-crystal silicon and calcium fluoride. Absolute expansivity was obtained over a broad range with an error less than 3 ppm. For silicon, this absolute method discriminates between earlier experiments showing some disagreement, and establishes with improved precision the temperature variation of the Grüneisen parameter γ in the region of particular interest (γ<0). For calcium fluoride the present x-ray measurements test a prediction of Ganesan and Srinivasan that γ should rise sharply below about 80°K. The prediction is not confirmed.

Determinação de fase vítrea em bauxitas refratárias

“…Os modelos de estrutura cristalina utilizados no refinamento para cada fase encontram-se nas referências [12][13][14][15][16][17]. Os dados para modelamento da estrutura cristalina das fases (parâmetros de rede, posições atômicas e fatores de ocupação) foram obtidos a partir de um CD-ROM específico para este fim: ICSD -Inorganic Crystal Structure Database.…”

Structural and spectroscopic studies on the alkali borohydrides MBH4 (M = Na, K, Rb, Cs)

“…The system was equipped with a closed-cycle helium Helix Model 22 Refrigerator [19]. The finely grinded powders were mixed with an internal silicon standard [20] and placed between two polyethylene terephtalate foils (Goodfellow) of 0.013 mm thickness. Measurements were performed during cooling from 300 to 10 K in the diffraction interval 10 • < 2θ < 100 • , with a step size of 2θ = 0.02 • , and a counting time of 2 s per step.…”

Some diffractometer test crystals: a summary

“…14-801. (s) Webster (1995b), (t) Webster (1992) Gabe (1981), (ac) Dam et al (1983), (ad) Wang et al (1985), ( Stadnicka et al (1992), (aj) Deshpande & Khan (1963), (ak) Webster (1995a), (al) Webster (1991b), (am) Lewis et al (1982), (an) Webster (1994), (ao) Barrett & Wallace (1954), (ap) Short & Roy (1963), (aq) Batchelder & Simmons (1964), (ar) Maslen et al (1993), ( …”

“…~:~t Referred to hexagonal axes. § § Converted from kxu units by multiplying by 1.00202 (see Batchelder & Simmons, 1964). References: (a) Marsh (1958), (b) J6nsson & Kvick (1972), (c) Legros & Kvick (1980), (d) Webster (1991a), (e) Carroll (1995), (f) Carroll (1997), (g) Spek (1987), (h) van Bommel & Bijvoet 11958), (i) Le Page et al, (1990), (j) Webster (1990), (k) Abrahams etal.…”