Please allow me to note that I have recently published in Philosophical Magazine a paper that presents a general approach to Gibbsian surface thermodynamics that includes a treatment of solid surfaces.  It can be accessed through the following link: 

http://www.informaworld.com/smpp/content~db=all~content=a792987191

If you send me your e-mail address I can send you a pdf of the "author's copy" (I cannot post it owing to copyright issues).  If interested, I can also send a pdf of an "author's copy" of a more comprehensive article that is to appear in Solid State Physics.