Dear all: I want to calculate the magnetic coupling constant J so that I can get the Cruie temperature. How can I achieve this by using QE? In some of the articles, the exchange parameter J was calculated by the energy difference of antiferromagnetism(AFM) state and ferromagnetism(FM) state. However, my initial antiferromagnetic moments usually cannot remain antiferromagnetic during the SCF process. Are these AFM(FM) states obtained by constrained magnetization calculation? Thanks for the help.