Highlights

• DFT & semi-empirical (SE, based on extended Hückel) models for electronic structure and transport calculations in one common interface
• New electrostatic model, allowing for inclusion of gates (and more!)
• Improved algorithms on many fronts, e.g. the basic two-probe model, geometry optimization, etc.
• Performance improvements
• New features, like bulk DOS, PDOS, and LDA+U/GGA+U (see the new tutorial!)
• A new, modern graphical user interface
• Fully parallel for DFT and SE, on two levels: MPI parallelization over clusters, and OpenMP threading for multi-core machines
• See more details below

The currently released package replaces both ATK 2008.10 and the preview versions 2009.xx and 2010.02.

License

All users will need a new license since we have changed license system to LM-X from X-Formation. Please contact support, if you have not already received one by email. Or, if you are a new user, please register to obtain a trial license.

Running calculations with the semi-empirical model requires a separate license feature, it's a different product compared to DFT.

Updated and new features

All users are strongly encouraged to read the Upgrade Guide (html | PDF). It contains a lot of useful information, esp. about the two-probe device algorithm. This document also discuess important points about backwards compatibility, which you also can read more about below.

Backengine (ATK)

In the ATK back-engine we note, among other things, the following major enhancements compared to 2008.10:

• Semi-empirical extended Hückel model and DFT combined in the same package, for electronic structure and transport calculations
  
• New electrostatic model
  • Include any number of (rectangular) metallic gate electrodes and dielectric regions at arbitrary positions, for realistic simulations of transistor-like structures
  • Ambient dielectric constant, to simulate a solvent
  • Charged systems, enabling calculations of single-electron transistors
• Improved algorithms
  • The most consistent two-probe model ever!
  • Double-contour integration, stabilize finite bias simulations (allows for a higher bias to be applied)
  • More accurate and flexible current integration model (compute current from transmission spectrum)
  • Possibility to do study thermionics by introducing a different temperature in the two leads for the current calculation
  • Use of electronic free energy instead of total energy, as appropriate in an open system
• Geometry optimization
  • More accurate forces
  • Considerably better relaxation algorithms (ATK 10.8 uses the ASE algorithms)
  • True relaxation under bias
• Performance
  • Faster self-energy calculations via new methods
  • Lower memory usage and faster convergence for many systems
  • Better utilization of multi-core computers (more parts threaded)
• Other new features
  • DOS
    • bulk DOS
    • optimized using unit cell symmetries
    • PDOS: projections on atoms and orbital shells for bulk and two-probe
  • Transmission spectrum
    • kpoint-resolved data automatically stored for later analysis
    • optimized using unit cell symmetries
  • LDA+U and GGA+U (tutorial)
  • Non-selfconsistent calculations for quick-and-dirty parameter checks (like k-point convergence)
  • Proper band structure calculations via symmetry points
  • Possibility to initialize an anti-parallel spin polarized calculation from the converged result of the parallel configuration
  • Extended list of available exchange-correlation potentials; over 300 available combinations, like for example:
    LDA: HL, PW, PZ, RPA, WIGNER, XA
    GGA: BLYP, BP86, BPW91, PBE, PBES, PW91, RPBE, XLYP
    For more details, see the manual.
• Miscellaneous
  
  • New license system
  • Simplified installation procedure, graphical installer also for Linux
  • The external code GPAW has been wrapped inside the ATK package, plus there is access to ASE
  • Unified, open file format (no more cryptic VNL file, just NC files)
  • Richer Python interface (more queries, less hidden variables and data)
  • Explicit boundary conditions
  • Change of naming of executable to "atkpython"
  • and more...

Graphical user-interface (VNL)

One of the immediately most visible updates is the graphical user interface, which has been completely redesigned. The workflow has been adjusted, and there is generally more functionality in the interface, to allow users to be more productive. The list of detailed new features is too long to publish - you will have to discover them as you work with the program. If there is something you can't find, ask us (preferably on the Forum), and we will consider if for future releases.

Some of the major new things in VNL 10.8 are:

• Builder
  • Unified interface for molecules, bulk and devices
  • Mirror, translate, copy/paste operations
• Script Generator
  
  • Powerful tool for interactively building up scripts in a logical way
  • Different detail levels of produced scripts: choose between compact, easy to read and understand scripts, or scripts with full details for learning more about the scripting interface and all the available options in ATK
• Plug-in modules
  
  • "Custom builder" for users to create their own builders
    • Several predefined ones are provided (this is e.g. where you now find the Nanotube Builder!)
  • "Custom analyzer" for specific analysis tasks, like I-V curves
• 3D viewer
  • improved graphical performance
  • change individual color and radius of individual atoms
  • orthographic projection
• Expanded databases for molecules and crystals
  • Added database for fullerenes
• Built-in file browser for easy access to calculations and scripts
• Miscellaneous
  • Proper band structure plots
  • Improved and extended import/export (CAR, CIF, XYZ, Cube)
    • VASP geometries can be imported and exported via a supplemental script
    • Export of raw data for band structure, electron density, and other 3D grids

Backwards compatibility

There are a couple of things to be aware of regarding this release.

• There is no compatibility with old NC or VNL files (even NC files from 2010.02).
• The Python syntax has changed, so those who are used to writing their own scripts are advised to read the manual carefully.

It is possible to import geometries (in Python files) from older versions either directly, or via a few simple intermediate steps.

• Molecules and bulk systems: as long as they are saved directly from VNL, Python scripts defining molecules and bulk systems (also PeriodicAtomConfigurations) can be directly dropped on the instuments in VNL 10.8.
• Two-probe systems: In many cases you can drop them directly, but if they contain repetitions in the electrodes or if they are constructed completely in the Atomic Manipulator (AM), you should re-open them in the AM and export the equivalent bulk system. Then open this system in the VNL 10.8 Builder and convert it to a device geometry. In fact, this work-flow is generally recommended, since it represents the new way to think of device geometries: make the central part, then specify which part is the electrode.

Platform support

To the best of our knowledge this release runs on pretty much all recent Windows versions and Linux distributions (sometimes specific libraries might be needed). For more information, see the detailed system requirements.

If you have a specific issue, please post it on the Forum (search first, it might already be solved!).

Known issues

There are no major known issues in this release, but there are a few minor ones, which will be resolved in an update version 10.8.1:

• Certain calculations under finite bias do not converge, or even give an error. A fix has been implemented.

Users may also take note of the following features which are not implemented yet, or not working optimally. These will be resolved in the next major release, version 11.2.

• Rhombohedral crystals in hexagonal setting are not imported correctly from CIF files.
• Support for cleaving crystals is limited to cubic structures. However, note that you do not need to cleave the structure to make a two-probe device configuration, if you already have proper electrode structures.
• No checkpoint file is made during the run.
• Some features from 2008.10 are not included in the new version (like Bloch states and transmission eigenvalues/eigenstates).
• The installer, when used in unattended mode, will install the software fine, but the license has to be set up manually.

ATK 10.8 in pictures

Here are some graphical illustrations of the features in ATK 10.8. Click each image for a larger version.

For some more examples of how to use the Builder, see e.g. the Au fcc mini-tutorial included in the Upgrade Guide.

To see the Script Generator in full action, see the spin mini-tutorial included in the Upgrade Guide.

This example is taken from the graphene junction tutorial.

This example is taken from an upcoming tutorial on using LDA+U to study MgO.

This example is taken from the tutorial called "Exploring graphene with ATK".

To learn more about ATK, please see our collection of tutorials.