https://www.researchgate.net/post/How_to_calculate_lattice_mismatch_in_thin_film[accessed Aug 21, 2016].

Thank you Roman,

I already read that discussion. but I did not not get any information related to my question.

btw i have few querries, why you choose GaAs 111 for a growth of a=4.26 and c=30.45A...the point here is the lattice constant for GaAs has a value, try to find that for your substrate and than compare that with "a" of your deposited film or  "c" if GaAs has a "c" parameter...

Dear Dillip, thanks for your comments. Because the growth is in c direction (c=30.45 A). so I think all the substrate have almost same differences. And reported results show the growth on GaAs(111) substrate.

As GaAs is cubic, so all the a,b and c parameters are same.

As growth of film is in c-axis, so should I try to compare c parameter or a parameter of film?

one is epitaxial growth which you expect on 111, means the resultant film also will be 111...is that correct? the other is lattice mismatch which is from lattice parameter only...

the resultant film show only (00l) peaks so it is in c-direction. lattice mismatch is from lattice parameter only , but which parameters??

why 001 instead of 111...little confusing or missing something...

For substrate, XRD shows (111) peaks but for material it shows (00l) peaks

I have read that inter planner distance between (111) plane of GaAs should be taken to calculate lattice mismatch of your grown film direction/ plane. 

https://www.researchgate.net/post/How_to_calculate_lattice_mismatch_in_thin_film[accessed Aug 21, 2016].