chemical vapor deposition
 

Hello, I'm working on the simulation of a chemical vapor deposition reactor with trichlorosilane and hydrogen. Fluent comes with a tutorial case for a reactor with silane and hydrogen. In this case the silicon deposited on the surfaces is named "Si(s)" and the parameters for this fluid are in the data-base of fluent. One thing that puzzles me is the value for the standard state enthalpy (heat of formation), which is 381 J/kmol. Shouldn't it be zero? Isn't the heat of formation of pure elements usually zero?? Probably this value won't influence the results, but I'd like to understand it anyway. Thanks, Paul