Two-photon momentum density in La2-xSrxCuO4 and Nd2-xCexCuO4.

We present calculations of the electron-positron momentum density for the high-T c superconductors La 2-x Sr x CuO 4 and Nd 2-x Ce x CuO 4 , together with experimental two-dimensional angular correlation of annihilation radiation (2D-ACAR) for Nd 2-x Ce x CuO 4 . The calculations are based on first-principles electronic structure obtained using the full-potential linearized augmented-plane-wave and the linear muffin-tin orbital methods