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Quantum chemistry computer programs are used in computational chemistry to implement the methods of quantum chemistry. Most include the Hartree–Fock (HF) and some post-Hartree–Fock methods. They may also include density functional theory (DFT), molecular mechanics or semi-empirical quantum chemistry methods.
Distortion free energy density. The distortion free energy density is a quantity that describes the increase in the free energy density of a liquid crystal caused by distortions from its uniformly aligned configuration. It also commonly goes by the name Frank free energy density named after Frederick Charles Frank .
The Crystallography Open Database ( COD) is a database of crystal structures. [1] Unlike similar crystallography databases, the database is entirely open-access, with registered users able to contribute published and unpublished structures of small molecules and small to medium-sized unit cell crystals to the database.
Potassium chromium sulfate. Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Chrome alum or Chromium (III) potassium sulfate is the potassium double sulfate of chromium. Its chemical formula is KCr (SO 4) 2 and it is commonly found in its dodecahydrate form as KCr (SO 4) 2 ·12 (H ...
Small molecules (up to ca. 1000 atoms) usually form better-ordered crystals than large molecules, and thus it is possible to attain lower R-factors. In the Cambridge Structural Database of small-molecule structures, more than 95% of the 500,000+ crystals have an R-factor lower than 0.15, and 9.5% have an R-factor lower than 0.03.
Inorganic Crystal Structure Database ( ICSD) is a chemical database founded in 1978 by Günter Bergerhoff at the University of Bonn in Germany and I. D. Brown at McMaster University in Canada. [1] [2] It is now produced by FIZ Karlsruhe in Europe and the U.S. National Institute of Standards and Technology. It seeks to contain information on all ...
A Wigner crystal is the solid (crystalline) phase of electrons first predicted by Eugene Wigner in 1934. [1] [2] A gas of electrons moving in a uniform, inert, neutralizing background (i.e. Jellium Model) will crystallize and form a lattice if the electron density is less than a critical value. This is because the potential energy dominates the ...
It is formed by precipitation from hydrothermal fluids, and contains by mass: 16.3% Tl, 47.3% Cu, 2.9% Ag, and 33.6% Se. [2] Crookesite is an opaque, bluish grey to pink toned brown metallic mineral crystallizing in the tetragonal system. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 6.9.