Accurate first-principles description of the antiferromagnetic state of La₂CuO₄

We show how an accurate first-principles treatment of the antiferromagnetic (AFM) state of La₂CuO₄ can be obtained without invoking any free parameters such as the Hubbard U. Both the magnitude and alignment of our theoretically predicted magnetic moment of 0.495 µ_B on Cu-sites along the (100) direction are in excellent accord with experimental results. The computed values of the AFM band gap (1 eV) and the exchange-coupling (-138 meV) match the corresponding experimental values. The magnetic form factor obtained from neutron scattering experiments is also well described by our calculations. Our study opens a new pathway for first-principles investigations of electronic structures and phase diagrams of cuprates and other complex materials.