A challenge in describing materials properties and synthesis is the large range of relevant length and time scales. While the properties one is eventually interested in are typically on a mesoscopic/macroscopic scale the fundamental mechanisms which cause this behavior are on an atomic scale. A key concept followed by many groups worldwide is therefore to combine electronic structure calculations (which provide an accurate description on the electronic scale) with approaches on a mesoscopic/macroscopic level. A prerequisite to apply this approach is a flexible and efficient electronic structure code. Specifically, there is a constant need to improve such a code with respect to efficiency (the algorithms efficient for small system are often not the most efficient ones for large systems and vice versa) and accuracy (implementation and testing of new exchange-correlation functionals, e.g., exact exchange). We have therefore developed a new plane-wave code [1] written in C++, which (i) utilizes a matrix-based formulation of density-functional theory and (ii) is completely object-oriented and modular. The matrix-based notation provides an efficient tool to describe new algorithms and gives direct access to fast BLAS3 (matrix-matrix) routines which are significantly faster than single-element or vector operations on modern computer architectures. The high level of modularity makes it easy for beginners to understand, modify and test parts of the code without affecting the rest of the program. Using this program it was possible to implement even complex algorithms such as the exact-exchange formalism and new electronic minimization algorithms in a few weeks rather than months

[1] S. Boeck, Development and Application of the S/PHI/nX Library,

Südwestdeutscher Verlag für Hochschulschriften, Saarbrücken, Germany,

ISBN 978-3-8381-1276-3

The Sphinx is a figure which appears in both Greek and Eyptian mythology. Both sphinx have the body of a lion and the head of a woman. The Greek sphinx has wings, the Egyptian does not. In Greek mythology, the Sphinx posed a riddle to all who seeked to pass. This riddle was at last explained by Edipus.

The Egyptian Sphinx was a goddess of wisdom and knowledge.