One of the outstanding advancements in electronic-structure density-functional methods is the Sankey-Niklewski (SN) approach [Sankey and Niklewski, Phys. Rev. B 40, 3979 (1989)]; a method for computing total energies and forces, within an ab initio tight-binding formalism. Over the past two decades, several improvements to the method have been proposed and utilized to calculate materials ranging from biomolecules to semiconductors. In particular, the improved method (called FIREBALL) uses separable pseudopotentials and goes beyond the minimal sp 3 basis set of the SN method, allowing for double numerical (DN) basis sets with the addition of polarization orbitals and d-orbitals to the basis set. Herein, we report a review of the method, some improved theoretical developments, and some recent application to a variety of systems.ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction With the increase in computational power, greater efforts have been made by the electronicstructure community to optimize the performance of quantum mechanical methods. Quantum mechanical methods have become increasingly reliable as a complementary tool to experimental research. A variety of methods exist ranging in complexity from semi-empirical methods to density-functional theory (DFT) methods to highly-accurate methods going beyond the one-electron picture. Judicious approximations enable the computational materials science community to more efficiently examine a wider range of materials questions.Otto F. Sankey was one of the early visionaries by, firstly, demonstrating that molecular-dynamics (MD) simulations can be coupled efficiently with electronic-structure methods to optimize structures and evaluate energetics of materials [1]. Secondly, his judicious approximations in the

Structurally, stilbene and azobenzene molecules exist in closed and open cis and trans forms, which are able to transform into each other under the influence of light (photoisomerization). To accurately simulate the photoisomerization processes, one must go beyond ground-state (Born-Oppenheimer) calculations and include nonadiabatic coupling between the electronic and vibrational states. We have successfully implemented nonadiabatic couplings and a surface-hopping algorithm within a density functional theory approach that utilizes local orbitals. We demonstrate the effectiveness of our approach by performing molecular dynamics simulations of the cis-trans photoisomerization in both azobenzene and stilbene upon excitation into the S1 state. By generating an ensemble of trajectories, we can gather characteristic transformation times and quantum yields that we will discuss and compare with ultrafast spectroscopic experiments.

Substitution into delafossite oxides is one promising method for the generation of improved catalysts for photochemical reactions such as the degradation of dyes and organic pollutants.