Theoretical support

Theoretical support: overview

In order to enable a deeper understanding of material properties, characterization methods and fabrication processes, theoretical support is an integral part complementing experimental methods conducted at the CzechNanoLab infrastructure. The theoretical analysis is based on state-of-the-art software tools, which are in part actively developed in house. Complex models that require high-performance computing use the computational resources provided by the Metacentrum and IT4Innovation facilities.

• Atomic-scale modelling
  • DFT modelling
    
  • Chemical reactions
  • Transport calculations
  • Symmetry analysis of crystals
  • Magnetic dynamics simulations
  • Empirical models
• Support for selected experimental techniques
  • TEM/SEM
  • Scanning probe microscopy
  • Diffraction methods
  • Nano-lithography
    

Atomic-scale modelling

Our aim is to provide a more in-depth insight into experimental measurements acquired in CzechNanoLab facilities. Therefore, we offer theoretical support including atomic-scale modelling. Based on different toolkits, we perform classical and quantum calculations depending on the complexity of the problem. Core competence is the optimization of the atomic and electronic structure of systems under study, which can be tailored to address specific properties or processes as required by the experiments.

DFT modelling

We provide theoretical support based on electronic structure calculations using total energy DFT calculations employing different codes:

• home-built large scale local orbital DFT Fireball code including thousands of atoms
  https://nanosurf.fzu.cz/wiki/doku.php?id=fireball
  https://github.com/fireball-QMD
• other available DFT codes: VASP, FHI AIMS, Abinit, Wien2K, KKR-GF

Optionally, we also employ calculations beyond single-determinant DFT methods such as GW, DMRG or DMFT.

Chemical reactions

• DFT calculations of interaction and activation energies of molecules on surfaces
• QM/MM simulations of on-surface chemical reactions
• dynamics of chemical reactions (rate equations, kMC)
  

Transport calculations

• Linear response Kubo
• Non-equilibrium Green’s function within Fireball and TranSiesta codes

Symmetry analysis of crystals

• https://bitbucket.org/zeleznyj/linear-response-symmetry/

Magnetic dynamics simulations

• https://spirit-docs.readthedocs.io

Empirical models

• Xtalsim - Atomistic structural model for semiconductor materials
  This software allows us to study semiconductor materials and heterostructures at atomistic length scales based on empirical interaction potentials. This computationally efficient model is also capable of simulating epitaxial growth processes to study the evolution of interface morphologies.

Support for selected experimental techniques

TEM/SEM

• Lorenz TEM simulations
• more SW

Scanning probe microscopy

• Gwyddion
• Probe Particle SPM model (high-resolution AFM, STM, KPFM)

Diffraction methods

• Jana
• X-ray diffraction of powder materials (Holy ??)

Nano-lithography

• Genesis Software