F+ laser performance and interaction of Cu, Ag and Au at the reduced oxygen coordination of MgO surface: first principles calculations

F+ laser performance and interaction of the title group IB transition metals at the reduced oxygen coordination of MgO surface were investigated using the TD and DFT methods of ab initio molecular electronic structure calculations. The considered ion clusters were embedded in simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces and the nearest neighbor ions to the F+ site were allowed to relax to equilibrium in each case. The F+ laser performance fades quickly as the reduced oxygen coordination decreases from 5 to 4 to 3. The relaxed excited states (RESs) of the defect containing surfaces are compact and deep below the conduction bands of the perfect MgO surface. The probability of orientational destruction of the center in laser experiment is expected to follow the order flat > corner > edge. The excited state at the edge has higher energy than that at the flat or at the corner. F+ is easily formed at the lower oxygen coordination and the disappearance of anisotrophy and 2p splitting observed in absorption of F+ at the surface follow the order corner > flat > edge. The Glasner-Tompkins relation is generalized to include the F+ bands at the reduced oxygen coordination of a metal oxide surface. As far as the adsorbate-substrate interactions are concerned, the F+ center enhances the adsorptivity of Ag, Cu and Au by ca. 1.91-3.33 eV and changes the nature of adsorption from physical adsorption to chemical adsorption. The adsorption. The adsorption energies follow the order Cu > Au > Ag and are explainable in terms of electrostatic potential curves, energy gaps and spin pairing. Cu and Ag act as electron donors while Au acts as electron acceptor and the MgO surface cannot be made semiconducting by F+ imperfection. (C) 2001 Elsevier Science B.V. All rights reserved.