Messages

16

General Questions and Answers / Re: geometric constraint

« on: May 21, 2011, 11:42 »

Yes but how many atoms in the central region? It seems to be 18+32+18=68, and that's why the index is not allowed to be larger than 67. But it's weird, because the electrodes have 32, so there is some mismatch somewhere. I can't say anything more without actually seeing the geometry.

17

News and Announcements / Bug fix update ATK 11.2.3 released

« on: May 17, 2011, 15:38 »

We released an update to ATK 11.2, ATK 11.2.3.

Changes in ATK 11.2.3 compared to 11.2.2 (see more details about that release in the previous post):

• There was one more small detail regarding the device DOS fix (for the NaN problem) that was not included in the 11.2.2 update. Now the problem should be finally solved.
• Some Hamiltonian matrix elements could become wrong near the boundaries; seems like a compiler bug, but it's fixed now and it cures convergence for systems where all charge would be lost near the edges.
• Better conversion of bulk systems to two probe systems. If you have problems with convergence, this could fix it! Please contact us for more information if you have convergence issues.
• The total energy entropy term was missing a factor 2 for non-spinpolarized systems.
• New feature: the "repeat" method on a bulk system now  repeats the  density matrix and Hamiltonian.
• VNL scripter: You can now select both periodic and Dirichlet boundary conditions for the FastFourier2DSolver.
• Calculation of forces now consumes less memory.
• Performance improvement: the calculation of the initial Hamiltonian, which is performed during the start-up phase of any calculation but also when you restore a calculation from an NC file, has been made a lot faster; the time goes from minutes to seconds.

Please uninstall ATK 11.2.x before installing this update, in order to avoid confusion with paths, desktop icons, etc.
 

18

General Questions and Answers / Re: How to setup verbosity_level in ATK11.2?

« on: April 19, 2011, 10:26 »

1.

Code: python

nlprint(transmission_spectrum.current())

See the manual

2. ATK 11.2 is equally excellent See this mini-tutorial.

19

General Questions and Answers / Re: How can get the spin-up and spin-down bands in atk-11.2.0

« on: April 19, 2011, 10:24 »

Contrary to earlier versions, in 11.2 you must explicitly choose a spin-polarized exchange-correlation potential to get a spin-polarized calculation.

20

General Questions and Answers / Re: How to setup verbosity_level in ATK11.2?

« on: April 18, 2011, 22:23 »

This feature is not yet implemented in 11.2. It will come soon

21

News and Announcements / Bug fix update ATK 11.2.2 released

« on: April 6, 2011, 12:23 »

We have found and fixed a few small bugs, and released an updated package, ATK 11.2.2.

Changes in ATK 11.2.2 compared to 11.2.0 (the last 3 were released already in 11.2.1):

• Some stress relaxations with fcc unit cells could fail unless you used a very high k-point sampling and mesh cut-off, esp. for GGA. The new algorithm applying the unit cell symmetries also to the stress tensor, this is less of an issue now.
• Device DOS could become NaN (not a number) if the unit cell had no symmetries. This is now fixed.
• VNL/Builder: further improvements in the algorithm for converting a bulk system to a device configuration: if no periodicity is found, the user can specify it manually
• Grouping is again available from the menu in the Builder
• Checkpoint file in MPI: if the user specified his own name for the checkpoint file, the slave nodes also tried to write to the file when running in parallel, causing the program to fail.
• LDOS: fixed an issue with parallelization
• Touch-ups to manuals

Please uninstall ATK 11.2.0 or 11.2.1 before installing this update, in order to avoid confusion with paths, desktop icons, etc.
 

22

News and Announcements / ATK 11.2 released

« on: March 3, 2011, 15:32 »

ATK 11.2 is is a major update compared to ATK 10.8 (not to mention 2008.10), and we urge all users to upgrade.

For more detailed information on new features etc, see the release letter.

Risk-free upgrade
Please note that upgrading from 10.8 to 11.2 is <i>risk free</i>, as there is 100% compatibility with 10.8 input and output (NC) files. Thus you will be able to enjoy the improved performance, not least memory-wise, and new features like transmission pathways and classical potentials, without worrying about upgrading your scripts etc.

A compact list of some new features include

• Improved performance and lower memory consumption
• Preconditioners, a new Poisson solver, and scattering states
• LDOS
• Transmission eigenchannel analysis
• Transmission pathways (local currents)
• Complex band structure
• Improved optimization via stress
• GUI updates
• Ghost atoms
• Molecular dynamics
• New engines: ATK-Classical and ATK-PlaneWave

We hope you all will enjoy ATK 11.2, and look forward to your feedback, and not least requests for new features in future versions!

23

General Questions and Answers / Re: Help:Segmentation fault

« on: October 6, 2010, 13:38 »

Probably you have run out of memory. Try a smaller basis set and a smaller mesh cut-off. If possible, make sure you are running with the FFT method, since the multigrid method uses a lot more memory.

24

News and Announcements / ATK 10.8 released

« on: July 7, 2010, 21:41 »

The final release of Atomistix ToolKit 10.8 is here!

This version brings, for the first time, both the fully functional DFT and semi-empirical extended Hückel models together in one single, greatly improved interface.

Highlights

• DFT & semi-empirical (extended Hückel) models for electronic structure and transport calculations
• 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 and LDA+U/GGA+U (see the new tutorial!)
• A new, modern graphical user interface

For more details, see the release letter.

25

News and Announcements / Testing syntax highlighting

« on: April 16, 2010, 13:56 »

test

Code: python

 for a in [1,2,3]:
    print a

26

General Questions and Answers / Re: one question about the conductance

« on: January 17, 2010, 20:46 »

See http://quantumwise.com/documents/manuals/ATK-2008.10/chap.litwoprobe.html#sect2.litwoprobe.conductance

Sometimes it makes sense to talk about the differential conductance too, that is dI/dV rather than I/V.

27

Future Releases / Re: My suggestion to the next VNL version about optimization

« on: November 11, 2009, 17:59 »

Duly noted.

For 1), the computation of stress is required, and this is not implemented in ATK, but it will be in the future.

2) is quite straightforward (for the positions part), in fact it can be done today with some inside knowledge. I can try to make an example and post it, if you want?

28

General Questions and Answers / MOVED: My suggestion to the next VNL version about optimization

« on: November 11, 2009, 17:57 »

This topic has been moved to Future Releases.

http://quantumwise.com/forum/index.php?topic=429.0

29

Scripts, Tutorials and Applications / Re: Relaxation under bias

« on: October 16, 2009, 11:38 »

The main reference on this would be PRB 67, 193104 (2003).

It should, however, be noted that the current implementation of forces in ATK might not be 100% correct under bias, although it should still give reasonable results. An update of this will be made soon.

30

General Questions and Answers / Re: can VNL calculate the variation of the current as a function of voltage?

« on: April 29, 2009, 11:12 »

You have only indented the definition of the two-probe method, not the actual execution of it.

You need

Code

for voltage in numpy.arange(0.0, 5.01, 0.1):
   two_probe_method = TwoProbeMethod(
       electrode_parameters = (left_electrode_parameters,right_electrode_parameters),
       exchange_correlation_type = exchange_correlation_type,
       iteration_mixing_parameters = iteration_mixing_parameters,
       electron_density_parameters = electron_density_parameters,
       basis_set_parameters = basis_set_parameters,
       iteration_control_parameters = iteration_control_parameters,
       energy_contour_integral_parameters = energy_contour_integral_parameters,
       two_center_integral_parameters = two_center_integral_parameters,
       electrode_voltages = (voltage, 0)*Volt,
       algorithm_parameters = two_probe_algorithm_parameters
   )

   if processIsMaster(): nlPrint(voltage)
   
   runtime_parameters = runtimeParameters(
       verbosity_level = 10,
       checkpoint_filename = 'C:/Users/617/Desktop/lih2li1.nc'
   )

    # Using initial density from self consistent calculation
    scf = executeSelfConsistentCalculation(
        twoprobe_configuration,
        two_probe_method,
        initial_calculation = scf,
        runtime_parameters = runtime_parameters
    )

   

    ######################################################################
    # Calculate physical properties
    ######################################################################
    current = calculateCurrent(
        self_consistent_calculation = scf,
        brillouin_zone_integration_parameters = brillouinZoneIntegrationParameters((1, 1)),
        green_function_infinitesimal = 1.0e-5*electronVolt,
        number_of_points = 100
    )
    if processIsMaster(): nlPrint(current)
    if processIsMaster(): file.addToSample(current, 'twoprobe_configuration', 'Current')