W1 – Materials Modeling and Simulation Training Workshop

Researchers in the Laboratory of Magnetism and High Energy Physics of University Mohamed V, Rabat, have a long-standing interest in computational physics simulations. They develop and explore how virtual models behave according to laws of nature instead of conducting experiments.

The objective is to predict, explain, and even control properties across the full range of

material structures. The simulation programs are used to understand the behaviors of electrons, atoms, molecules and materials in order to support the development of materials and devices.

The workshop Materials Modeling and Simulation will be conducted by Prof. Dr. Abdelilah Benyoussef and provides a forum for Researchers, Master and PhD students to design new materials and/or optimize emerging materials with consideration for their environmental impact and application for solar energy conversion and energy storage.

Master and PhD students will gain skill and backgrounds, which can directly guide for the right choice of materials and design of various products and structures and help meeting our future global energy needs in an environmentally responsible way which is one of the greatest challenges of the twenty first century.

The tutorial will cover the fundamentals and the practical use of state-of-the-art codes for the calculation of the electronic structure of bulk solids, surfaces to foster an open dialog between experimentalists and theoreticians to identify the most promising research directions related to energy, storage and environments.

Who Should Attend the workshop?

Introduction to Materials Modeling and Simulation Workshop

Bridging the gap between theory and practice: fast-track development of future photovoltaic materials and devices
By Dr. Teodor Todorov, IBM/NY, USA

Materials for Emerging Energy Technologies
Prof. Ahmed Ennaoui QEERI/HBKU, Doha, Qatar

Continuum modeling and FEM simulations
Professor Said Ahzi QEERI/HBKU, Doha, Qatar

Computer time with tutors on hand:

Density Functional Theory Studies of  Electronic and Optical Properties of Photovoltaic materials.

Introduction:

The main aim of this practical session is to calculate some materials properties including lattices constants, band structure, and density of state, optical properties …..

These properties depend on the total electronic wave function which may be calculated using Schrodinger equation or depend on the total electronic density which may be calculated using the Density Functional Theory (DFT).

Many codes have been used to calculate the electronic density. For example the Wien2k code is based on the Kohn-Sham formalism of the density functional theory using Full- Potential Linearized  Augmented Plane Wave method (FP-LAPW).KKR-CPA,VASP …

The structure of the Wien2k – code:

The Self consistency cycle of the Wien code consist of five independent programs:

• LAPW0: generates the potential from a given charge density
• LAPW1: computes the eigenvalues values and eigenvectors
• LAPW2: computes the valence charge density from the eigenvectors
• CORE: computes the core states and densities
• MIXER: mixes the densities generated by LAPW2 and CORE with the density of the previous iteration to generate a new charge density.

 

The interface of Wien2k:

Using the Wien2k interface the following steps are realized:

• Structure generator
  • Space group selection
  • Import cif file
• Step by step initialization
  • Symmetry detection
  • Automatic input generation
• Self consistency calculations
  • Magnetism (Spin-polarization)
  • Spin-orbite coupling
  • Forces (automatic geometry optimization)
• Guided tasks
  • Energy band structure
  • DOS
  • Electron density
  • X-ray spectra
  • Optics
• K mesh generation
  • X kgen (generates k-mesh and reduces to irreducible wedge using symmetry)
  • Always “add inversion” except in magnetic spin-orbit calculations
    • Time inversion holds and E(k)=E(-k)
  • Always “shift” the mesh for Self consistency cycle
    • Gap often at gamma
  • Small unit cells and metals require large k-mesh (1000-100000)
  • Large unit cells and insulators need only 1-10 k points
  • Mesh is good if nothing changes and Self consistency terminates after few iterations (3)
  • Use an even finer meshes for DOS, optics….

 

Properties with WIEN2k:

• Energy bands
  • Classification of irreducible representations
  • Character-plot
• Density of states
  • Including partial DOS with l and m character
• Electron density, potential
  • Total-, valence-, difference-, spin-densities of selected states
  • 1D, 2D and 3D –plots
  • X-ray structure factor
• Total energy and forces
  • Optimization of internal coordinates
  • Cell parameter only via total energy
  • Elastic constants for cubic cells
  • Phonons via supercells
• Spectroscopy
  • Core level shifts
  • X-ray emission, absorption, electron-energy-loss (with core holes)
  • Optical properties
  • Fermi surfaces (2D and 3D)

• Practical examples:
  • CdTe; SnO2; ZnO;

The KKR-CPA first-principles theory:

The KKR-CPA is a first-principles theory of the electronic structure of random solid solution alloys  in which electronic structure problem is solved using multiple scattering theory Green’s function methods and the effects of disorder on the electronic structure are treated using the CPA. The CPA can be viewed as a mean field theory that provides the best single-site theory of the effects of disorder on the electronic structure. The KKR-CPA allows direct calculation of the configurationally averaged properties of the alloy—configurationally averaged DOS, charge density and Bloch spectral function (BSF). We review some recent conceptual improvements of the Korringa–Kohn– Rostoker (KKR) Green function method for electronic structure calculations. After an introduction into the KKR–Green function method we present an extension of this method into an accurate full-potential scheme, which allows calculation of forces and lattice relaxations.

• The interface of KKR-CPA:

 

• Installing under LINUX, Operating systems and compilers
• Running the AKAI-KKR program specx
• Input for the AKAI-KKR program specx

Objectives:

• Prepare an input file for KKR-CPA, defining all the necessary parameters.
• Study the convergence of the ground state energy with respect to the cutoff energy.
• Determine the relaxed lattice constant.
• Output and plot the density of states (DOS).
• Create the “out” file containing complete information on the Kohn-Sham bandstructure used.

 

• Practical examples:

• • Al doped ZnO; Transparent Conductive Oxide
  • Band-gap engineering of SnO2: controlling the band structure and optoelectronic properties of few-layer SnO2 via strain engineering
• Other practical examples using Wien2K, KKR-CPA or Quantum Espresso:
  • Chalcogenide Perovskites; BaZrS3 for photovoltaic applications
  • Alloying Chalcogenide Perovskites for Optimized Photovoltaic Application: BaZr1−xTixS3
  • Organic/inorganic hybrid perovskite CH3NH3PbI3 to improve the solar-conversion efficiency of dye-sensitized solar cells
  • Phosphorene as a promising anode material for different rechargeable Batteries
  • Hydrogen storage in doubly substituted Mg based hydrides Mg5MH12 (M = B, Li) and Mg4BLiH12

Program

Apply to participate