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Journal Article

The Crvstallographic Society of America

William Parrish1
01 Dec 1948-American Mineralogist (GeoScienceWorld)-Vol. 33, pp 749-784
About: This article is published in American Mineralogist.The article was published on 1948-12-01 and is currently open access. It has received 7 citations till now.
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Journal ArticleDOI
TL;DR: In this article, an independent measurement of the heat capacity of copper potassium sulfate has been made, and the relation $C=\frac{A}{{T}^{2}}$ appears to be obeyed, the value of the specific heat constant $A$ being $5.5.
Abstract: The heat capacities of a number of metals have been measured in the region below 1\ifmmode^\circ\else\textdegree\fi{}K, using the technique of adiabatic demagnetization. Copper, silver, platinum, palladium, tungsten, molybdenum, and sodium have been investigated. Apart from sodium, all exhibit a linear dependence of electronic specific heat on temperature. The values of $\ensuremath{\gamma}$ are in agreement with those obtained in the liquid helium region, except in the case of tungsten, which gives $\ensuremath{\gamma}=3.5\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ cal/mole ${\mathrm{deg}}^{2}$ in contrast to the previous value $\ensuremath{\gamma}=1.8\ifmmode\pm\else\textpm\fi{}0.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ cal/mole ${\mathrm{deg}}^{2}$ reported in the literature. Sodium exhibits an anomalous peak in its specific heat curve. A low-temperature, martensitic-type transformation is advanced as a likely cause of this behavior.In the course of the experiments, an independent measurement of the heat capacity of copper potassium sulfate has been made. The relation $C=\frac{A}{{T}^{2}}$ appears to be obeyed, the value of the specific heat constant $A$ being $5.8\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}R$ ${\mathrm{deg}}^{2}$/mole.

57 citations

Journal ArticleDOI
TL;DR: In this paper, a technique for carrying out ab initio Hartree-Fock calculations on systems of infinite three-dimensional periodicity was presented, which represents an adaptation of standard molecular basis set expansion techniques and fully utilizes translational and point-group symmetry to simplify the calculations.
Abstract: A technique is presented for carrying out ab initio Hartree-Fock calculations on systems of infinite three-dimensional periodicity. The method represents an adaptation of standard molecular basis-set expansion techniques and fully utilizes translational and point-group symmetry to simplify the calculations. It is shown that the expression for total energy may be written as a sum of pairwise interactions between neutral charge units consisting of a nucleus and a localized compensating electronic charge. The resulting sums are rapidly convergent. The technique is illustrated with sample calculations on face-centered-cubic lattices of hydrogen, lithium, and sodium. Generalization to systems of lower symmetry is discussed.

9 citations

Journal ArticleDOI
TL;DR: The first identification of the use of veszelyite, a rare hydrated copper-zinc phosphate, as green pigment was made in the ancient Maya Classic period (AD 250-800) as discussed by the authors.
Abstract: Blue-green mosaic and polychrome masks and funerary offerings from the royal tombs of Calakmul, Mexico, were analysed by scanning electron microscope equipped with energy dispersive X-ray spectroscopy, (SEM-EDS), X-ray diffraction (XRD), and particle induced X-ray emission (PIXE). This led to the first identification of the use of veszelyite, a rare hydrated copper-zinc phosphate, as green pigment. Analyses of a geological sample of this mineral have been done to confirm the characterization of this Mayan pigment, which might help determine pre-Columbian trade routes of precious and luxury objects in the ancient Maya Classic period (AD 250-800).

4 citations