Properties of Elements in TDE

The calculation of formation properties for any compound requires thermodynamic properties for the constituent elements. Property values for these elements are not evaluated dynamically by TDE, but are fixed within the program.

Standard States

The standard state for the gaseous elements is the ideal-gas state for all temperatures with pressure p = 101.325 kPa.

The standard state for carbon is graphite. Graphite exists as a single phase to, at least, near T = 4000 K, as noted in the 4th Edition of the NIST JANAF-Thermochemical Tables.

The phase for the standard state of sulfur, bromine, and iodine is defined as the condensed phase at saturation pressure for pressures < 101.325 kPa. For pressures > 101.325 kPa, the standard state is the ideal gas. Consequently, the phase of the standard state is a function of temperature, and the enthalpy and entropy for these elements exhibit discontinuities associated with various phase changes.

Iodine, I2
386.75 K: Crystal-to-Liquid
457.666 K: Liquid-to-Ideal Gas

Bromine, Br2
265.90 K: Crystal-to-Liquid
332.503 K: Liquid-to-Ideal Gas

368.30 K: Crystal(II)-to-Crystal(I)
388.36 K: Crystal(I)-to-Liquid
432.02 K: Liquid-Liquid lambda transition
882.117 K: Liquid-to-Ideal Gas (diatomic sulfur)

Properties of C(graphite), Br2(all phases), I2(all phases), and S(all phases) are taken from:

NIST-JANAF Thermochemical Tables, Malcolm W. Chase, Jr. (editor); Washington, DC ; New York : American Chemical Society: American Institute of Physics for the National Institute of Standards and Technology, 1998.

Properties of H2, N2, O2, F2, Cl2 in the ideal gas state were derived statistically as listed in:
Thermodynamics of Organic Compounds in the Gas State. M. Frenkel, G. J. Kabo, K. N. Marsh, G. N. Roganov, R. C. Wilhoit. Thermodynamics Research Center, 1994.