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Optical Properties and van der Waals–London Dispersion Interactions in Berlinite Aluminum Phosphate from Vacuum Ultraviolet Spectroscopy
Author(s) -
Dryden Daniel M.,
Tan Guolong L.,
French Roger H.
Publication year - 2014
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.12757
Subject(s) - van der waals force , refractive index , chemistry , band gap , spectroscopy , exciton , dispersion (optics) , analytical chemistry (journal) , materials science , condensed matter physics , optics , physics , molecule , optoelectronics , organic chemistry , chromatography , quantum mechanics
The interband optical properties of single‐crystal berlinite AlPO 4 have been investigated in the vacuum ultraviolet ( VUV ) range using VUV spectroscopy and spectroscopic ellipsometry. The complex optical properties were directly determined from 0.8 to 45 eV. Band gap energies, index of refraction and complex dielectric functions, oscillator index sum rule, and energy loss functions were calculated through Kramers–Kronig transformation. Direct and indirect band gap energies of AlPO 4 over the absorption coefficient range of 33–11 000 cm −1 are 8.06 and 7.89 eV, respectively. The index of refraction at 2 eV, n vis , is 1.51. The interband transition features at 10.4, 11.4, 14.2, 16.2, 17.3, 21, 22.5, 24.5, and 31 eV were indexed and correlated with the electronic structure of AlPO 4 . Strong similarities were observed between AlPO 4 and its structural isomorph SiO 2 in the exciton and interband transitions, resulting from the similarity of their constituent tetrahedra and the strong electron localization therein. The London dispersion spectrum for AlPO 4 was calculated, and the Hamaker coefficients for AlPO 4 with various interlayers were calculated using the Lifshitz method. These results elucidate the role of phosphate complex anions on the electronic structure and van der Waals forces in important organic and inorganic systems.