The Particle Tracking feature introduces two new concepts to Ansys Chemkin’s Surface Kinetics options: particle surface site density and initial surface coverage. Surface site density is the number of active chemical sites per surface area where adsorption, desorption, and chemical reaction can take place. The value of surface site density is specified in the site data section of the surface mechanism. Besides the site density, surface species that can exist on the particle surface site must be declared in the site data section. These surface species are defined as either elements or fractions of molecular structure, from the precursors, that are neither made into the particle core nor released into the gas phase. More information about syntax and rules regarding site data is provided in Site Data of the Chemkin Input Manual .

The following example declares a surface site named "EDGE " on the dispersed (or particle) material "SOOT ". The site density of "EDGE " is given as 3.341 x 10^-9 [mole/cm² ]. Two surface species H(SE) and OPEN(SE) are declared on site "EDGE ". According to the thermodynamic data, H(SE) represents a surface-bonded hydrogen atom and OPEN(SE) is an open (or empty) surface site.

Declaration of surface site on dispersed material

MATERIAL SOOT
! declare dispersed material 
DISPERSED
END
! declare name, site density, and surface species 
SITE/EDGE/    SDEN/3.341E-9/   
   H(SE) 
   OPEN(SE) /NATIVE/  
END
! declare bulk species that makes up the particle core
BULK/GRAPHITE/ C(B) /1.8/
END
! thermodynamic data for surface and bulk species
THERMO
OPEN(SE)          102903C   0               I  0300.00   5000.00  1000.00      1
 0.14901664E+01 0.16621256E-02-0.06687204E-05 0.12908796E-09-0.09205334E-13    2
-0.07074018E+04-0.08717785E+02-0.06705661E+01 0.07181499E-01-0.05632921E-04    3
 0.02142298E-07-0.04168562E-11-0.07339498E+03 0.02601595E+02                   4
H(SE)             121286C   0H   1          I  0300.00   5000.00  1000.00      1
 0.14901664E+01 0.16621256E-02-0.06687204E-05 0.12908796E-09-0.09205334E-13    2
-0.07074018E+04-0.08717785E+02-0.06705661E+01 0.07181499E-01-0.05632921E-04    3
 0.02142298E-07-0.04168562E-11-0.07339498E+03 0.02601595E+02                   4
C(B)              121286C   1               S  0300.00   5000.00  1000.00      1
 0.14901664E+01 0.16621256E-02-0.06687204E-05 0.12908796E-09-0.09205334E-13    2
-0.07074018E+04-0.08717785E+02-0.06705661E+01 0.07181499E-01-0.05632921E-04    3
 0.02142298E-07-0.04168562E-11-0.07339498E+03 0.02601595E+02                   4
!
END
REACTIONS
!
!   nucleation
!
2A4 => 32C(B) + 20 H(SE) + 28.72 OPEN(SE)        9.0E+09   0.5     0.0
    NUCL
!
END