Soluble semiconductors AAs[Se.sub.2] (A = Li, Na) with a direct-band-gap and strong second harmonic generation: a combined experimental and theoretical study

Identification and single-crystal x-ray diffraction studies of AAs[Se.sub.2] (where A = Li, Na) as a new class of polar direct-band gap semiconductors is described. The theoretical studies which confirmed with the experimental results indicated the [gamma]-NaAs[Se.sub.2] to have the highest static SHG coefficient of 337.9 pm/V, among materials with band gaps larger than 1.0 eV.