Multiphase carbon and its properties in complex mixtures Page: 3 of 19
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van Thiel, paper No. 6.30
Multiphase carbon and its properties in complex mixtures.
M. van Thiel and F.H. Ree
Lawrence Livermore National Laboratory, P. 0. Box 808, Livermore,
California 94550, USA.
Abstract. We describe some key features of a carbon three-phase equation
of state and a high-pressure high temperature mixture model in which it is
used. Electronic terms in the carbon model have been investigated with
INFERNO (atom in a cell model). The Lindeman criterion for melting is
rederived for the anisotropic structure of the graphite lattice. The
curvature of the graphite melting lina is constrained by the evidence for
the positive slope of the diamond melting line. The importance of carbon
is apparent from various experiments on shock generated mixtures. The
model allows us to estimate the energy of carbon clusters produced in a
detonating mixture. A cluster model with specific surface structure is
used to predict this energy.
At temperatures of 2000 K and above, the rates of most decomposition
reactions are sufficiently fast that they go to completion in less than
.01 microseconds. Such temperatures occur behind shock and detonation
waves, in laser ablation processes, and in the high pressure atmospheres
of the Jovian planets. Computer simulation of such hydrodynamic systems is
also common practice in research and development programs. The ability
to compute the equation of state of high.-temperature and high-pressure
mixtures is therefore important for practical problems as well as for
planetary and condensed matter physics.
The multiphase chemical equilibrium theory, CHEQ, was developed to
compute the equation of state of such high-pressure and high-temperature
mixtures [Ree 1984]. In this theory gaseous products, interacting via
dispersion forces or rapidly rotating dipoles and multipoles, are
described by a first principles statistical mechanics approach. -Condensed
(covalent or ionic) systems are formulated with Grkneisen-like forms. The
description of carbon in its liquid-, graphite-, and diamond phases [van
Thiel and Ree 1989) is such an approach, within the framework of the Gibbs
free energy minimization method of the chemical equilibrium code (CHEQ).
Table I underscores the importance of graphite in such hot high pressure
mixtures by the percentage of carbon (in atoms/total number of molecules)
in the equilibrium mixtures of a number of well known systems. At low
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van Thiel, M. & Ree, F.H. Multiphase carbon and its properties in complex mixtures, article, September 1, 1990; California. (https://digital.library.unt.edu/ark:/67531/metadc1212167/m1/3/: accessed April 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.