Site Links:

HiTempThermo Home

Gas-Phase Data

Condensed-Phase Data

Equilibrium Calculation

Industry Pages
 
Join Mailing List

Molekel Install

Basis Sets

Databases

Software Apps

Administrative Links 		News Notes       Privacy & Security   

Description of Gas-Phase Data (CHEMKIN) Format

The input format for the CHEMKIN application consists of four 80-character text records, numbered 1 thru 4 in column 80.

In addition to the fourteen (14) fit coefficients, the input also contains the species' name, its elemental composition, computational temperature limits, and an indication of its phase (gas, liquid, or solid).

Note: Spaces have been added to the example below for readability.  
Select (click) Radio Button to highlight item in example data box below.
       Name of Species
       Date (not used by CHEMKIN)
       First Element Descriptor (Element, Number of occurrences)
       Second Element Descriptor (Element, Number of occurrences)
       Third Element Descriptor (Element, Number of occurrences)
       Fourth Element Descriptor (Element is Blank and Number = 0 if none)
       Phase (State)
       Low-Temperature
       High-Temperature
       Transition (Break) Temperature
       Fifth Element Descriptor (if needed) (Element is Blank and Number = 0 if none)
       7 Upper Temperature Range Coefficients ( fitting parameters a1 - a7 )
       7 Lower Temperature Range Coefficients ( fitting parameters a1 - a7 )
    Note: Example has three (3) elements out of a possible five (5).
[DESCRIPTION]     CAUTION: Data presented here is for illustration purposes only; DO NOT USE.
These fits can be used with the CHEMKIN software package and are defined by:

Cp(T) / R   =   a1  +  a2T  +  a3T 2  +  a4T 3  +  a5T 4

[DELTA]H°(T)   =   a1   +   a2 T   +   a3 T 2   +   a4 T 3   +   a5 T 4   +   a6
  RT  2  3  4  5 T

S°(T)   =   a1 ln(T )   +   a2T   +   a3 T 2   +   a4 T 3   +   a5 T 4   +   a7
R  2  3  4

where
     T is temperature (K), 
     Cp(T) is heat capacity (kcal/mol-K) at temperature T,
     H°(T) is enthalpy (kcal/mol) at temperature T, 
     S°(T) is entropy (kcal/mol-K) at temperature T, and  
     R = 0.001987 kcal/mol-K

Note that [DELTA]H°(T) = H°(T) - H°(298) + [DELTA]Hf°(298), where [DELTA]Hf°(298) is the species heat of formation at 298K, H°(T) is the standard enthalpy at temperature T, and H°(298) is the standard enthalpy at 298K.

Fits were carried out over two separate temperature ranges. The low, high, and break temperatures for these two fits are given at the end of the first line of the thermo data. For example, for the species BCl, the data were fit over the ranges 300 - 1000K and 1000 - 3000K. (Also see example above.)

The subsequent three lines of numbers in the data record are the fitting parameters a1 - a7 for each fit. The parameters for the high-temperature range are given first, followed by those for the low-temperature range. More information concerning this format can be found in the Chemkin III manual.
Content Comments to Mark Allendorf
Site Comments to Michelle Medlin
Last Modified on Oct 9, 2009
[ORNL]
Site Maintained at
Sandia National Laboratories for the
US Department of Energy (DOE)