Regensburg 2004 – wissenschaftliches Programm
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O: Oberflächenphysik
O 28: Postersitzung (Elektronische Struktur, Grenzfläche fest-flüssig, Halbleiteroberflächen und -grenzflächen, Magnetismus und Symposium SYXM, Methodisches, Nanostrukturen, Oberflächenreaktionen, Teilchen und Cluster, Zeitaufgelöste Spektroskopie)
O 28.10: Poster
Mittwoch, 10. März 2004, 16:00–19:00, Bereich C
Elctronic structure of MgSO4 crystals — •V.V. Maslyuk1,2, C. Tegenkamp1, T. Bredow3, and H. Pfnür1 — 1Institut für Festkörperphysik, Appelstr.2 D-30167 Hannover, Germany — 2Uzhhorod National University, Pidgirna St.2 88000 Uzhhorod, Ukraine — 3Institut für Theoretische Chemie, Am Kleinen Felde 30 D-30167 Hannover, Germany
Typically, the crystallographic structures of minerals are quite well investigated, but there is not much knowledge about their electronic structures. As one candidate of an insulator consisting chemically of more than two different elements, we investigated the crystallographic and electronic structure of MgSO4 and kieserite (MgSO4 · H2O), respectively. Starting with kieserite with 36 atoms per unit cell, we determined the electronic structure by ab–initio calculations. Using CRYSTAL03 the lattice parameters were calculated within an accuracy better than 0.01 Å by choosing basis sets for magnesium and oxygen taken from MgO and for sulfur taken from CaSO4 including also d–orbitals. In order to calculate the band gap of kieserite, the method of hybrid mixing of Hartree–Fock and DFT hamiltonians was used. The band gap at the Γ–point was detemined to be 7.4 eV. To support the theoretical calculations, first photoelectron– and electron energy loss spectroscopy experiments have been performed. Thereby, bulk kieserite crystals have been used. Obviously, the effect of surface relaxation effects and defects are small, because the measured band gap agrees quite well with the theoretical findings. Nevertheless, our calculations will be further refined.