M2As2Q5 (M = Ba, Pb; Q = S, Se): a source of infrared nonlinear optical materials with excellent overall performance activated by multiple discrete arsenate anions

M2As2Q5 (M = Ba, Pb; Q = S, Se) have been screened out by combined experiments and theoretical calculations as a new source of IR NLO materials. Interestingly, they exhibit excellent overall performance activated by multiple discrete arsenate anions.