# VASP (Vienna Ab-Initio Package)

When studying atomic scale systems, VASP is my weapon of choice, even though other ab-initio codes exist with similar performance. Results obtained with this program can be processed using several available tools, and more information on the program itself can be found both in the manual and tutorials. Below I’ll list some I have had experience with myself:

## Information and tutorials

• VASP tutorial 2010-2014:   Short tutorial on VASP I gave at Ghent University (2010, 2013, and 2014) and Catholic University of Leuven (2012). It should get you started doing the most standard (simple) calculations: e.g. a relaxation, a self consistent calculation, a DOS or band structure calculation,…
• VASP manual:  Online manual containing all help information for the VASP program.
• VASP forum:  If you have a question or problem you can’t find the solution for in the manual then this forum might help you out. (many problems meet their answer there.)
• DFT-Error-wiki:  Error-handling is a bit of a lost art when it comes to scientific programming. In general you discover that something is wrong when the program just stops functioning. In other cases you can get errors which are more or less helpful. On this wiki, some colleagues and I are trying to catalogue known error-messages combined with some helpful tips for resolving them.

## Tools and Software

• HIVE-STM plotter:    When looking at surfaces, the geometry doesn’t always tell you the entire story. Comparison with experiment can be done via Scanning Tunneling Microscope (STM) images. Though STM images might tell a lot, they miss one key piece of information: what atom type you are actually looking at. To make comparison between theoretical geometries and experimental structures possible, simulating STM images based on the calculated structures can be a great help. This is a little piece of software I wrote just to do that: generate pseudo-STM images. It does this using the VASP PARCHG file and is based on the Tersoff-Hamann method. You can add contours and the positions of atoms can be shown. The height of the simulated tip can be varied or the charge density of the isosurface can be set, images can be saved as .bmp for future use, and much more. (Windows/linux via wine)
(How to obtain the program: just send me an email and ask me 😉 )
• HIVE3-tools:  A set of useful command-line tools that allow for the post-processing of VASP data. This program can be found on the UGent HPC, and should be loaded as the “HIVE” module. This software is not freely available, as it is a WIP.
• VESTA:  To visualize your geometry and charge density you can use this program. It reads POSCAR and CHGCAR files (if the OUTCAR file is present) and allows for quick rendering of the geometry and or iso-charge surface. There are export options for a large range of graphical output files (both raster and vector format).
Also, simple geometrical data, such as distance between 2 specific atoms or the angle between 3 atoms, can be obtained easily. It is very user friendly, and easy to use. The program is able to handle both VASP 4.X and VASP 5.X geometry data. (Windows/Mac/Linux)
• P4VASP:  This is a second visualization tool to investigate your VASP data. Not as handy and professionally looking as VESTA, and also not that easy to install. An interesting feature though (this alone makes it worth the trouble of installing) is the option to view the geometry during relaxation as an animation, with arrows representing (for example) the forces acting upon the atoms. (Windows/Linux/Mac)
• VMD:  Advanced program, allowing for the animation of trajectories and advanced rendering of structures. Unfortunately, it requires quite some work from the user to make it work. In addition, it appears not well up to date with recent VASP file-formats. (Windows/Linux/Mac)