High-throughput electronic band structure calculations: Challenges and tools (original) (raw)

The AFLOW standard for high-throughput materials science calculations

Computational Materials Science, 2015

The Automatic-Flow (AFLOW) standard for the high-throughput construction of materials science electronic structure databases is described. Electronic structure calculations of solid state materials depend on a large number of parameters which must be understood by researchers, and must be reported by originators to ensure reproducibility and enable collaborative database expansion. We therefore describe standard parameter values for k-point grid density, basis set plane wave kinetic energy cut-off, exchange-correlation functionals, pseudopotentials, DFT+U parameters, and convergence criteria used in AFLOW calculations.

Algorithms for Korringa-Kohn-Rostoker electronic structure calculations in any Bravais lattice

1997

We present some algorithms for improvements of band theory calculations based on the Korringa-Kohn-Rostoker method and on the coherent potential approximation, in the cases of ordered metals and random alloys. The purpose of our work was to develop a code flexible enough to deal on equal footing with any lattice geometry. The algorithms proposed are designed to achieve an arbitrary accuracy and to minimize the required computational efforts. In particular, we describe ͑i͒ an efficient and accurate method for the calculation of the KKR structure constants, and ͑ii͒ an adaptive method for the Brillouin zone integration. These algorithms have been tested for a free-electron Green's function and by explicit calculations for a number of systems and, when possible, discussed in comparison with other methods. Ab initio calculations for hexagonal close packed and face centered cubic Ti and for Cu 0.75 -Pt 0.25 random alloys are presented.

MIKA: a multigrid-based program package for electronic structure calculations

2002

A general real-space multigrid algorithm MIKA (Multigrid Instead of the K-spAce) for the self-consistent solution of the Kohn-Sham equations appearing in the state-of-the-art electronic-structure calculations is described. The most important part of the method is the multigrid solver for the Schr\"odinger equation. Our choice is the Rayleigh quotient multigrid method (RQMG), which applies directly to the minimization of the Rayleigh quotient on the finest level. Very coarse correction grids can be used, because there is in principle no need to represent the states on the coarse levels. The RQMG method is generalized for the simultaneous solution of all the states of the system using a penalty functional to keep the states orthogonal. Special care has been taken to optimize the iterations towards the self-consistency and to run the code in parallel computer architectures. The scheme has been implemented in multiple geometries. We show examples from electronic structure calculati...

Self Consistent Calculations of Electronic Properties of Systems with an Energy or a Band Gap

2012

Unquestionably, the BZW-EF method i rofoundtr t o"?lL"tit" as (a) it provides accurare, electronic, structurar, tanspo( opucal,-;d ryF; p-p€xtio of semiconductors, including band gaps, and (b) it ushers in an era ofab-initio, r"ir-"iorirt""t, and accurate predictions of properties of novel materials-Hence, Bzw-EF caiculations Ln inform and guirle the design and fabrication of deYices based on finite or crystalline materials witfi energr or band gapg respectively.

Large scale electronic structure calculations using the Lanczos method

Computational Materials Science, 1994

First-principles simulations of high-Z metallic systems using the Qbox code on the BlueGene/L supercomputer demonstrate unprecedented performance and scaling for a quantum simulation code. Specifically designed to take advantage of massivelyparallel systems like BlueGene/L, Qbox demonstrates excellent parallel efficiency and peak performance. A sustained peak performance of 207.3 TFlop/s was measured on 65,536 nodes, corresponding to 56.5% of the theoretical full machine peak using all 128k CPUs.

Energy Band Structures of Semiconductors

The physical properties of semiconductors can be understood with the help of the energy band structures. This chapter is devoted to energy band calculations and interpretation of the band structures. Bloch theorem is the starting point for the energy band calculations. Bloch functions in periodic potentials is derived here and a periodic function is shown to be expressed in terms of Fourier expansion by means of reciprocal wave vectors. Brillouin zones are then introduced to understand energy band structures of semiconductors. The basic results obtained here are used throughout the text. Nearly free electron approximation is shown as the simplest example to understand the energy band gap (forbidden gap) of semiconductors and the overall features of the energy band structure. The energy band calculation is carried out first by obtaining free-electron bands (empty lattice bands) which are based on the assumption of vanishing magnitude of crystal potentials and of keeping the crystal periodicity. Next we show that the energy band structures are calculated with a good approximation by the pseudopotential method with several Fourier components of crystal potential. Also k · p perturbation method for energy band calculation is described in detail. Another method "tight binding approximation" will be discussed in connection with the energy band calculation of superlattices in Chap. 8. 1.1 Free-Electron Model It is well known that the physical properties of semiconductors are understood with the help of energy band structures. The energy states or energy band structures of electrons in crystals reflect the periodic potential of the crystals and they can be calculated when we know the exact shape and the magnitude of the crystal potentials. The shape and the magnitude of the potential are not determined directly from any experimental methods, and thus we have to calculate or estimate the energy bands by using the assumed potentials. Many different approaches to calculations of energy bands have been reported, but in this textbook we will deal with several methods, which are not so difficult to understand. We begin with the most simplified method to calculate electronic states in a model crystal.

On the reliability of linear band structure methods

2007

We discuss an efficiency of various band structure algorithms in determining the Fermi surface (FS) of the paramagnetic ErGa3. The linear muffin-tin orbital (LMTO) in the atomic sphere approximation (ASA) method and three full potential (FP) codes: FP-LMTO, FP linear augmented plane wave (FLAPW), and FP local orbitals (FPLO) methods are employed. Results are compared with electron-positron (e-p) momentum densities reconstructed from two dimensional angular correlation of annihilation radiation (2D ACAR). Unexpectedly, none of used modern FP codes is able to give satisfying description of the experimental data that are in perfect agreement with LMTO-ASA results. We suspect that it can be connected with a different choice of the linearization energy.

BoltzTraP. A code for calculating band-structure dependent quantities

A program for calculating the semi-classic transport coefficients is described. It is based on a smoothed Fourier interpolation of the bands. From this analytical representation we calculate the derivatives necessary for the transport distributions. The method is compared to earlier calculations, which in principle should be exact within Boltzmann theory, and a very convincing agreement is found. Program summary Title of program: BoltzTraP Catalogue identifier: ADXU_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADXU\_v1\_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: none Programming language used: Fortran 90 Computer: The program should work on any system with a F90 compiler. The code has been tested with the Intel Fortran compiler Operating system: Unix/Linux RAM: bytes up to 2 GB for low symmetry, small unit cell structures No. of lines in distributed program, including test data, etc.: 1 534 213 No. of bytes in distributed program, including test data, etc.: 27 473 227 Distribution format: tar.gz External routines: The LaPack and Blas libraries are needed Nature of problem: Analytic expansion of energy-bands. Calculation of semi-classic integrals. Solution method: Smoothed Fourier expansion of bands. Running time: Up to 3 hours for low symmetry, small unit cell structures.