Dear Hongsheng Zhao, I am not sure about what you want to ask. But I guess if what you mean by "internal degrees" is what you have specified, a system having or not having the internal degrees does not depend on the shape of of the cell. You may check the input description of pw.x, I think the "no internal degrees of freedom" is mentioned for scf calculation is because in "relax" the atomic coordinates are allowed to evolve during the calculation, while when scf is specified only electronic configurations have the freedom to evolve keeping all the atomic coordinates fixed. I hope that I have answered your question, excuse me if I have misunderstood your real puzzle. Best wishes, Ge Xiaochuan
2011/7/22 <pw_forum-request at pwscf.org>: > My vague understanding of internal degrees of freedom
