Before Sutton, interfaces were described vaguely. Sutton introduced a rigorous geometric approach using the . The idea is simple: when two crystals rotate relative to each other, some atomic positions overlap. The density of these overlapping sites defines the Σ value.
If you have searched for the term , you are likely a graduate student, researcher, or advanced undergraduate looking for the gold-standard text on this subject. You are looking for the seminal work by A.P. Sutton and R.W. Balluffi. interfaces in crystalline materials sutton pdf
If you are a PhD student studying hydrogen embrittlement along grain boundaries, a postdoc simulating dislocation-precipitate interactions, or an engineer designing radiation-resistant alloys, this text is your fundamental reference. Before Sutton, interfaces were described vaguely