The Large Second‐Harmonic Generation of LiCs2PO4 is caused by the Metal‐Cation‐Centered Groups.

Abstract: We evaluated the individual atom contributions to the second harmonic generation (SHG) coefficients of LiCs₂PO₄ (LCPO) by introducing the partial response functionals on the basis of first principles calculations. The SHG response of LCPO is dominated by the metal‐cation‐centered groups CsO₆ and LiO₄, not by the nonmetal‐cation‐centered groups PO₄ expected from the existing models and theories. The SHG coefficients of LCPO are determined mainly by the occupied orbitals O 2p and Cs 5p as well as by the unoccupied orbitals Cs 5d and Li 2p. For the SHG response of a material, the polarizable atomic orbitals of the occupied and the unoccupied states are both important. [ABSTRACT FROM AUTHOR]