Overview

flair is an electronic structure program based on density functional theory. It uses the full potential augmented plane wave method (FLAPW) to solve the Kohn-Sham equations. The FLAPW method is a very accurate all electron method to solve the electronic structure problem of both crystals and low dimensional structures. Some of its unique features are described in

M.Weinert, G. Schneider, R. Podloucky, and J. Redinger, FLAPW: Applications and Implementations, J. Phys.: Condens. Matter 21, 084201 (2009).

gem is a python module for the generation and manipulation of crystal structures and in fact all kinds of atomic structures. It also facilitates and simplifies the setup and analysis of electronic structure calculations.

Put together flair and gem provide a great tool for learning electronic structure calculations.

It has a number of advantages over the available alternatives:

• Both gem and flair are free software. You can install them on your home computer or on your lab computer and use them long after the end of this class. For the reminder of your time as a grad student at OSU and for your entire career.
• Visualization is built in.
• Low dimensional structures are straight forward.
• Magnetic systems, including anti-ferromagnetic structures, are straight forward.
• You only need to specify the important parameters for a particular calculation. No click through a semi-complete (and long) list of parameters.
• Calculations are not restricted to a single server. No bottleneck just before the project report is due.
• Many advanced features such as STM image calculations and surface diffraction patterns are available. They are probably beyond what you want to aim for in your class project but might proof useful later in your career.
• If you like programming and python in particular you will like gem. Everything can be programmed and automated.

There are some drawbacks at this time:

• No optical properties at this time. This is not a limitation in principle, we just haven’t yet implemented dipole matrix elements. Anyone with mathematical and programming skills interested in a senior thesis?
• In flair a few elements in the period table are more difficult to set up than others. Again this is not a limitation in principle, we haven’t yet implemented a feature called semi core states . Ask your professor (Guenter Schneider, Weniger 401a) for help.

I am very interested in learning from as many students as possible what works well, what works better or worse than the alternatives, and how I can improve both gem and flair and the documentation and tutorials that go with it. Feedback from students who used or tried to use both gem/flair and Wien2K is very much appreciated.