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Wen-Dan Cheng

Publications and source records attributed to Wen-Dan Cheng.

3 recordsLinked to original sources

Synthesis, crystal structure, and optical properties of LiGd5P2O13, a layered lithium gadolinium phosphate containing one-dimensional Li chains.

A lithium gadolinium phosphate crystal, LiGd5P2O13, has been synthesized by a high temperature solution reaction and solved by single-crystal X-ray diffraction data. The structure is monoclinic, space group C2/m, with unit cell parameters a = 18.645(3), b = 5.6257(5), c = 12.014(2) A, beta = 117.55(6)degrees, V = 1117.3(3) A3, and Z = 4. LiGd5P2O13 presents a new structural type and is built up from [Gd5P2O13]- layers and one-dimensional Li chains with an unusual Li-Li distance. The optical properties were investigated in terms of the absorption and emission spectra. Additionally, the calculations of band structure, density of states, dielectric constants, and refractive indexes were performed with the density functional threory method. The obtained results tend to support the experimental data.

Journal Article↗

Theoretical study of two-photon absorption in donor-acceptor chromophores tetraalkylammonium halide/carbon tetrabromide.

Two-photon absorption properties of a series of donor-acceptor chromophores of tetraalkylammonium halide/carbon tetrabromide ([NR4h.CBr4], h = Cl, Br, I; R = Me, Et, Pr) complexes are investigated in terms of the calculated results by the time-dependent density functional theory (TDDFT) technique combined with the sum-over-states (SOS) method. The modeling two-photon absorption spectra show that these charge-transfer complexes have large two-photon absorption (TPA) cross sections and the [NEt4I.CBr4] has the largest TPA cross section delta with the value of 5.0 x 10(-45) cm4 s photon(-1). The maximum values of delta increase with increasing separations between the donor/acceptor in the order Cl...Br < Br...Br < I...Br for [NEt4h.CBr4] complexes; however, the TPA cross sections delta vary slightly as the size of the alkyl group increases from methyl to propyl for the bromide as a donor, and the maximum wavelength of the TPA peak lambdamax indicates a bathochromic shift. The charge transfers from the halide anion to the carbon tetrabromide make a significant contribution to the excited states, and the donor-acceptor charge transfer plays an important role in the TPA activity, whereas changes in size of alkyl group do not make a substantial contribution to TPA.

Computer Simulation↗

Se2(B2O7): a new type of second-order NLO material.

Exploration on the compounds in the selenite-borate system led to the discovery of a new second-order NLO material, Se2B2O7, with a SHG efficiency of about 2.2 times that of KDP (KH2PO4). Its structure features a 3D network with helical tunnels, and it is transparent in the UV and visible region. The compound is a wide band gap semiconductor.

Journal Article↗