Heteroanionic LaBrVIO4 (VI = Mo, W): Excellence in Both Nonlinear Optical Properties and Photoluminescent Properties

Five heteroanionic oxybromides, LaBrMoO4,LaBrWO4, (La0.9Sm0.1)BrMoO4, (La0.9Sm0.1)BrWO4, and (La0.9Dy0.1)BrWO4, were grown by a high-temperaturesalt flux method. Millimeter-sized crystals were collected after saltflux was removed by DI water. The crystal structures were accuratelydetermined by single-crystal X-ray diffraction. LaBrMoO4 is isostructural to LaBrWO4. The substitution of lanthanumfor rare earth elements does not change the crystal structure. LaBrWO4 is the first acentric tungsten-containing compound of theREBrVIO(4) (RE = Y, La-Lu; VI = Mo, W) system. Thebonding picture of LaBrWO4 was understood by crystal orbitalHamilton population calculations (COHP) and electron localizationfunction (ELF) analysis, which confirmed the uncommon 4 + 1 coordinationof tungsten surrounded by oxygen atoms. Linear optical propertiessuch as bandgaps, infrared spectrum (IR), and birefringence of thetitle compounds were recorded in this work. LaBrMoO4 exhibitsa moderate second harmonic generation (SHG) response of 0.47xKH(2)PO(4) (KDP) for incident 1064 nm radiation.LaBrWO4 and (La0.9Dy0.1)BrWO4 exhibit superior SHG responses of 1.66x KDP and 3.71xKDP for samples for incident 1064 nm radiation, respectively. Allmeasured samples exhibited type-I phase matching behavior. Densityfunction calculations (DFT) verified that the optical properties ofLaBrMoO(4) and LaBrWO4 are predominantly controlledby [VIO5](VI = Mo,W) units. Via therare earth elements Sm and Dy doping, LaBrMoO4 and LaBrWO4 emit visible lights of various wavelengths upon UV lightexcitation. The distortion of lambda-shaped one-dimensional (1D) [VIO5](VI = Mo,W) strands plays an importantrole in enhancing nonlinear optical properties and photoluminescentproperties within LaBrWO4 and (La0.9Dy0.1)BrWO4 compared with LaBrMoO4.