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Ondrej Certik

Publications and source records attributed to Ondrej Certik.

4 recordsLinked to original sources
arXiv2022

The State of Fortran

A community of developers has formed to modernize the Fortran ecosystem. In this article, we describe the high-level features of Fortran that continue to make it a good choice for scientists and engineers in the 21st century. Ongoing efforts include the development of a Fortran standard library and package manager, the fostering of a friendly and welcoming online community, improved compiler support, and language feature development. The lessons learned are common across contemporary programming languages and help reduce the learning curve and increase adoption of Fortran.

cs.PL↗
arXiv2018

The virtual element method for eigenvalue problems with potential terms on polytopal meshes

We extend the conforming virtual element method to the numerical resolution of eigenvalue problems with potential terms on a polytopal mesh. An important application is that of the Schrodinger equation with a pseudopotential term. This model is a fundamental element in the numerical resolution of more complex problems from the Density Functional Theory. The VEM is based on the construction of the discrete bilinear forms of the variational formulation through certain polynomial projection operators that are directly computable from the degrees of freedom. The method shows a great flexibility with respect to the meshes and provide a correct spectral approximation with optimal convergence rates. This point is discussed from both the theoretical and the numerical viewpoint. The performance of the method is numerically investigated by solving the Quantum Harmonic Oscillator problem with the harmonic potential and a singular eigenvalue problem with zero potential for the first eigenvalues.

math.NA↗
arXiv2007

Numerical solution of the radial Dirac equation in pseudopotential construction

In the present work we study numerical solution of the radial Dirac equation in a specific case - ab-initio pseudopotential generating process - which is needed within the electronic structure calculations using a Density Functional Theory (DFT) combined with a pseudopotential method. We give a brief introduction to DFT, derive the radial Dirac and Schrodinger equations, show how to solve them both for a given energy and as an eigenvalue problem using a known asymptotic behavior of the solution. Next we compare the nonrelativistic and relativistic eigenvalues for one electron atom. Finally we state a few words about the computer implementation.

physics.atom-ph↗