Thanks for your reply. I see that you agree with me that we should have μv = μ∞ at equilibrium. In the last line, did you mean "μv0 = μ∞ then..."? I am still not understanding the physics behind it.
I have been reading the book "Nanostructures and Nanomaterials" by G. Cao and Y. Yang, and was intrigued by the following passage in page 33:
"Assuming the vapor of solid phase obeys the ideal gas law, for the flat surface one can easily arrive at:
μv − μ∞ = −kTlnP∞, where μv is the chemical...