title: X-ray diffraction, X-ray photoelectron spectra, crystal structure, and optical properties of centrosymmetric strontium borate Sr2B16O26.
abstract: We report results of X-ray diffraction (XRD) and valence band X- ray photoelectron (VB-XPS) spectra for strontium borate Sr(2)B(16)O(26). The X-ray structural analysis shows that the single crystals of Sr(2)B(16)O(26) crystallize in the monoclinic space group P2(1)/c with a = 8.408(1) A, b = 16.672(1) A, c = 13.901(2) A, beta = 106.33(1) degrees , and Z = 4. The crystal structure consists of a 3D network of the complex borate anion [B(16)O(20)O(12/2)](4-), formed by 12 BO(3) triangles and four BO(4) tetrahedra, which can be viewed as three linked [B(3)O(3)O(4/2)](-) triborate groups bonded to one pentaborate [B(5)O(6)O(4/2)](-) group and two BO(3) triangles. Using this structure, we have performed theoretical calculations using the all-electron full potential linearized augmented plane wave (FP-LAPW) method for the band structure, density of states, electron charge density, and the frequency-dependent optical properties. Our experimental VB-XPS of Sr(2)B(16)O(26) is compared with results of our FP-LAPW calculations. Our calculations show that the valence band maximum (VBM) and conduction band minimum (CBM) are located at Gamma of the Brillouin zone (BZ) resulting in a direct energy gap of about 5.31 eV. Our measured VB-XPS show reasonable agreement with our calculated total density of states for the valence band that is attributed to the use of the full potential method.
authors: Institute of Physical Biology, South Bohemia University, Nove Hrady 37333, Czech Republic. maalidph@yahoo.co.uk
authors: Ali Hussain
authors: AH
authors: Reshak
authors: S
authors: S
authors: Auluck
authors: I V
authors: IV
authors: Kityk
authors: Xuean
authors: X
authors: Chen
mesh_terms: D001881:Borates / Q000138:chemical synthesis / Q000737:chemistry*; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D004583:Electrons; D008958:Models, Molecular; D015394:Molecular Structure; D013324:Strontium / Q000737:chemistry*
chemical_list: D001881:Borates; C543851:strontium borate; D013324:Strontium