3.2.1. Element Data

All chemical species in the reaction mechanism must be composed of chemical elements or isotopes of chemical elements. Each element and isotope must be declared as a one- or two-character symbol. The purpose of the element data is to associate atomic weights of the elements with their character symbol representations. For the elements appearing on the periodic chart, the atomic weight (in grams per mole) stored internally in the KINetics module. For isotopes, a one- or two-character symbol must be input to identify each isotope, and a symbol and an atomic weight (in grams per mole) for each must be defined. The same symbol must be used in the thermodynamic data to identify the elemental composition of species involving the isotope. Once an isotope has been so defined, it is treated exactly as a new element. If an ionic species is used in the reaction mechanism (that is, OH+), an electron must be declared as the element E.

Element data must start with the word ELEMENTS (or ELEM), followed by any number of element symbols on any number of lines. Element symbols may appear anywhere on a line, but those on the same line must be separated by blanks. Any line or portion of a line starting with an exclamation mark (!) is considered a comment and will be ignored. Blank lines are ignored.

If an element is on the periodic chart, then only the symbol identifying the element need appear in the element data.

Note:  The elements that KINetics and Chemkin recognize are as follows: H, HE, LI, BE, B, C, N, O, F, NE, NA, MG, AL, SI, P, S, CL, AR, K, CA, SC, TI, V, CR, MN, FE, CO, NI, CU, ZN, GA, GE, AS, SE, BR, KR, RB, SR, Y, ZR, NB, MO, TC, RU, RH, PD, AG, CD, IN, SN, SB, TE, I, XE, CS, BA, LA, CE, PR, ND, PM, SM, EU, GD, TB, DY, HO, ER, TM, YB, LU, HF, TA, W, RE, OS, IR, PT, AU, HG, TL, PB, BI, PO, AT, RN, FR, RA, AC, TH, PA, U, NP, PU, AM, CM, BK, CF, ES, FM, D, E

For an isotope, the atomic weight must follow the identifying symbol and be delimited by slashes (/). The atomic weight may be in integer, floating-point, or “E” format, but internally it will be converted to a floating-point number. For example, the isotope deuterium may be defined as D/2.014/. If desired, the atomic weight of an element in the periodic chart may be altered by including the atomic weight as input just as though the element were an isotope.

Example 3.2: Equivalent ways to describe element information shows several equivalent ways to describe element information. In this example the elements are hydrogen, oxygen, nitrogen, and the isotope deuterium.

Example 3.2: Equivalent ways to describe element information

ELEMENTS  H D /2.014/ O N END

ELEM         ! ELEM is equivalent to ELEMENTS
 H
 D / 2.014 /
 O
 N
END          ! an END line is optional

ELEM H
ELEM D/2.014/
ELEM O
ELEM

Table 3.2: Summary of the rules for element data summarizes the rules for element data.

Table 3.2: Summary of the rules for element data

RuleDescription
1The first element line must start with the word ELEMENTS (or ELEM).
2

Element or isotope names are either one-or two-character symbols.

3

An isotope name (that is, a name not on the periodic chart) must be followed by its atomic weight (in grams per mole) delimited by slashes.

4

Each element or isotope should be declared only once; however, duplicated element symbols will be ignored.

5

An element or isotope name may appear anywhere on the line.

6

Any number of element or isotope names may appear on a line, and more than one line may be used.

7

Element or isotope names that appear on the same line must be separated by at least one blank space.

8

An element or isotope name that begins on one line may not continue to the next line.

9

Any blank spaces between an element or isotope name and the first slash are ignored and any blank spaces between slashes and an atomic weight are also ignored. However, no blank spaces are allowed within an element name or an atomic weight.

10

There may be more than one ELEMENT statement.

11

All characters following an exclamation mark are comments.