qw stanford feb2010 new · 2010-03-05 · »two-probe systems negf using the transiesta method...
TRANSCRIPT
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What’s new
@
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Speed-up of ATK 2008.10 compared to 2008.02
System Speed-up Memory reduction
Azafulleroid (molecule, 97 atoms) 1.1 15%
6x6x6 MgO (bulk, 432 atoms, Gamma point) 3.5 38%
6x6x6 MgO (k-point sampling (2,1,1)) 2.3 32%
8x8x8 MgO (bulk, 1,024 atoms, Gamma point) 5.4 63%
AuSiAu (two-probe, 1,166 atoms*) 3.2 50%
The speed-up measures how many times faster the new version is compared to 2008.02 (a factor 2 means twice faster), while the memory reduction is given in percent (50% means half the memory).
* 782 atoms in scattering region, 1,166 in equivalent bulk
Speed-up and memory reduction for the two-probe system with 1166 Si and Au atoms. The two distinguishable regimes (breakpoint at 350 ks for the red curve) are the equivalent bulk run and the two-probe calculations, respectively.
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Supercluster parallel scaling & speedup
Model: Au-Si nanowire-Au
CPU cores
Speedup
Total calculation time
0
20
40
60
80
100
120
140
160
4 8 16 32 64 128
CPU Cores
Cal
cula
tion
time
(hou
rs)
ATK 2008.02
ATK 2008.10
ATK 2008.10
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New ATK
QuantumWise builds new platform
Old ATK
� Needed to restructure the old software,
to get solid foundation for growth
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Development
Functionality
Time20102009 2011 20132012
New ATK
old ATK
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Agile development, short development cycles
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Releases
2008.10 : ”Old” ATK + VNL
2009.06 : ”New” VNL + ATK-SE
2010.01 : ATK-DFT alfaVNL-beta, ATK-SE update
Windows
2010.02 : Redhat
----------------------------------------------
2010.07 : ATK-DFT, VNL releaseATK-SE update, LDA+U
2010.12 : Improved accuracy
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Features ATK 2008.10 versus 2010.02
�Electronic structure calculations» SIESTA-based method, plus inclusion of indirect atom pairs for improved accuracy
» Up to double-zeta double polarized (DZDP) numerical atomic orbital basis sets, with detailed user control of basis set parameters
» Norm-conserving (Troullier-Martins) pseudopotentials provided for all elements, with possibility to use customized pseudopotentials
» LDA-PZ, GGA-PBE GGA-revPBE exchange correlation potentials (also spin-polarized)
» Fermi level smearing for improved convergence stability
» Customizable Broyden/Pulay mixing for self-consistent scheme
» Monkhorst-Pack k-point sampling grids
�Calculation of» molecular spectra
» band structure of periodic structures
» Eigenfunctions (molecular orbitals, Bloch functions)
» Mulliken population analysis
» Real-space electron density and effective potential
» Forces (analytic Hellmann-Feynman)
�Ion dynamics» Quasi-Newton or steepest descent relaxation
» Constraints: fixed positions
» Nudged Elastic Band (NEB) transition state analysis
�Transport calculations» Two-probe systems NEGF using the TranSIESTA method (self-energy coupling to semi-infinite leads)
» Green's function description of non-equilibrium electron distribution in scattering region
» Finite bias
» Ability to treat heterogeneous systems through multi-grid solution to Poisson's equation
» Simulation of electrostatic gate
�Transport analysis» Transmission coefficients (k-point resolved) and transmission spectrum
» Spin-dependent current and conductance/resistance
» Transmission eigenvalues and real-space eigenchannels
» Surface density of states
» Real-space local density of states
» Fast evaluation of linear response current
» Collinear spin-torque transfer
» Molecular Projected Self-Consistent Hamiltonian eigenvalues and real-space eigenfunctions
�Work-flow control» Store and restore the state of a calculation for deferred analysis, restart, or initialization of a new calculation via the self-consistent density matrix
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”New” ATK – new features
� Electrostatic gates, dielectric regions
� Simulation of charged systems + ambient dielectric constant
� Fast self-energy calculations, Krylov methods
� Double-contour integration, stabilize finite bias simulations (go to higher bias)
� New two-probe model; the to-date most consistent model
3-terminal device Single Electron Transistor
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New algorithms (1)
Electrode self-energies, timings
H. H. Sørensen et al., PRB 79, 205322 (2009)
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New algorithms (2)
D. E. Petersen et al., J. Comp. Phys. 227, 3174 (2007)
Green’s function calculation
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NanoLanguage 2.0
� NanoLanguage 1.0 was introduced in 2006» Purpose: map ATK 2.0/TranSIESTA functionality into Python
� NanoLanguage 2.0 is the next step in the evolution» Goal (for the future): A unified object-oriented platform for all types of atomic-scale simulations
� Open and efficiency-enhancing» Many more query methods and user functions
» Simple, open storage classes
» GUI operations become user functions
» Unified file format (see next slide)
� Similar to ASE 2.0» Support for multiple “calculators” (ATK-SE, DFT, GPAW, …)
� And many other small and large improvements...!
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File handling
� Unified file format
» All data stored in NetCDF files
» Open format (binary)
» User functions for storing and retrieving
data from files
» No more VNL files
� VNL interacts directly with file system
» File browser in GUI
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ATK-DFT 2010.07 tentative plan
� Feature-complete compared to 2008.10
� Improved relaxations -------------�(already in 2010.02)
� NEB calculations
� Calculation of stress
� Improved convergence for two-probe systems, automatic detection of appropriate complex contour
� Improved analysis: PDOS, current density
� Improved parallel performance
� Parallelized memory
� Spin-polarized LSDA
� LDA+U
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ATK-DFT features 2010.12
� GGA
� Ultrasoft pseudopotentials
� Optimized basis sets
� Correction for BasisSet superposition error
� (1-probe)
� (Non-colinear spin)
� (Finite-element grids)
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ATK-SE 2010
� Same functionality as ATK-DFT, but with
semi-empirical model
� Force module for relaxations
� Slater-Koster models (tight binding)
New module: ATK-Classical
� Brenner potentials for C and H
� EMT potentials for metals
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VNL 2010.01
• Bulk Builder
• Surface Builder
• Molecular Builder
• Database
• Scripter
• Job Manager
• 3D viewer (iso-surface, contour plotvolume plot)
• Atomic Manipulator (two-probe builder)
• (Display of bonds)
Comparison with VNL 2008.10
• Custom Builder
• Custom Analyzer
• Improved performance
• Improved workflow
• Support for several calculators
• More functionality in instruments
• (Two probe editor)
• (Support for easy input/output of external formats CIF, XYZ, old ATK, …)
• (Visualization of trajectories)
• ….
New Features
Features in () will be available in 2010.07
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.com
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Publication list
Full abstracts, links to article sourceSearchable (also in abstracts)>140 scientific articles published with ATK in 2008/2009>200 in total (since 2004)
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Tutorials
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New features delivered via the Forum
� Analysis extensions» Bulk DOS
» Projected DOS (PDOS)
» Symmetry reduction of k-point sampling for transmission & DOS
» Effective mass and band gap for semiconductors
» I–V curves
» Atomization energy
» Current density
� Geometry setup and manipulation» Graphene nanoribbons
» Nanotubes
» Relaxation under bias
� Plotting tools» K-point resolved transmission
» Band structure
» Voltage drop
� Miscellaneous» XYZ file manipulations
» Extracting data from VNL files
» Converting old ATK files to NanoLanguage