Hi, I'm having a trouble understanding the definition of interfacial energy in solid.
Say we have a coherent interface between phase A and B.
Normally we accept an equation:
Wab = Eav + Ebv - Eab
Wab: Work of Adhesion, Eav: Interfacial energy btw phase A and vacuum (surface energy of A),
Ebv: Interfacial energy btw phase B and vacuum (surface energy of B),
Eab: Interfacial energy btw phase A and B
Therefore, Eab = Eav + Ebv - Wab
My confusion arises with the sign of the eventual interfacial energy.
Lets say phase A is only composed of a atoms and phase B is only composed of b atoms.
In most cases, bond energy a-b is stronger(more negative value) than that of the average of a-a and b-b.
For the interface A/B to be made, N a-a bonds and N b-b bonds should be broken to make 2N a-b bonds.
Eav= N Eaa, Ebv = N Ebb, Wab = 2N Eaa
Since Eab < 0.5(Eaa+Ebb), this process lowers the overall energy(endothermic) and it is energetically favorable to form an interface.
However, if that's true, the interfacial energy of A/B should be negative. But, in most cases in papers, interfacial energies are presented as positive values.
I'm very confused of these conflicting situations. Is my approachment wrong?
It woud be very helpful to get some advises or solutions to my problem. Thank you.
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