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Your search keyword '"Varga, Kálmán"' showing total 5 results
5 results on '"Varga, Kálmán"'

1. Solution of the time-dependent Schrbdinger equation using time-dependent basis functions.

Author

Varga, Kálmán

Subjects
*SCHRODINGER equation, *WAVE functions, *THEORY of wave motion, *PROBLEM solving, *IONIZATION (Atomic physics), *MATHEMATICAL models, *LIGHT absorption, *ABSORPTION spectra, *DIMERS
Abstract

The time-dependent Schrödinger equation is solved by using an explicitly time-dependent basis. This approach allows efficient reflection-free time propagation of the wave function. The applicability of the method is illustrated by solving various time-dependent problems including the calculation of the above threshold ionization of a model atom and the optical absorption spectrum of a sodium dimer. [ABSTRACT FROM AUTHOR]

Published
2012
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2. Time-dependent density functional study of transport in molecular junctions.

Author

Varga, Kálmán

Subjects
*ELECTRON transport, *NANOSTRUCTURES, *DENSITY functionals, *NONEQUILIBRIUM thermodynamics, *GREEN'S functions, *WAVE functions, *MOLECULAR spectra
Abstract

Electron transport in nanostructures is calculated and compared using a time-independent and a time-dependent first-principles framework. The time-independent approach uses the nonequilibrium Green's-function technique to calculate the current, while the time-dependent method extracts the current from the time propagated wave function. The approaches have been tested using gold-benzene-dithiolate-gold and gold-bipyridine-gold molecular junctions. The reasons for the differences in the current-voltage curves predicted by the two methods are discussed. [ABSTRACT FROM AUTHOR]

Published
2011
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3. Multidomain decomposition approach to time-dependent density functional calculations.

Author

Goncharov, Vladimir A. and Varga, Kálmán

Subjects
*DENSITY functionals, *MATHEMATICAL decomposition, *WAVE functions, *LIGHT absorption, *GRAPHENE, *TEST systems
Abstract

A multidomain decomposition method is presented for time-dependent density functional calculations. The multidomain decomposition approach divides the coordinate space into subdomains where local solutions are generated. The subdomain solutions are used as basis states to describe the time propagation of electronic wave functions in the whole system. The applicability and flexibility of the approach are demonstrated on various test systems including the calculation of the photoabsorption cross section of a graphene ribbon and a light-harvesting triad. [ABSTRACT FROM AUTHOR]

Published
2011
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4. Solution of few-body problems with the stochastic variational method II: Two-dimensional systems

Author

Varga, Kálmán

Subjects
*RANDOM variables, *FORTRAN 90, *WAVE functions, *MATHEMATICAL complexes, *QUANTUM dots, *FEW-body problem
Abstract

A computational approach is presented for efficient solution of two-dimensional few-body problems, such as quantum dots or excitonic complexes, using the stochastic variational method. The computer program can be used to calculate the energies and wave functions of various two-dimensional systems. Program summary: Program title: svm-2d Catalogue identifier: AEBE_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEBE_v1_0.html Program obtainable from: CPC Program Library, Queen''s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 5091 No. of bytes in distributed program, including test data, etc.: 130 963 Distribution format: tar.gz Programming language: Fortran 90 Computer: The program should work on any system with a Fortran 90 compiler Operating system: The program should work on any system with a Fortran 90 compiler Classification: 7.3 Nature of problem: Variational calculation of energies and wave functions using Correlated Gaussian basis. Solution method: Two-dimensional few-electron problems are solved by the variational method. The ground state wave function is expanded into Correlated Gaussian basis functions and the parameters of the basis states are optimized by a stochastic selection procedure. Accurate results can be obtained for 2–6 electron systems. Running time: A couple of hours for a typical system. [Copyright &y& Elsevier]

Published
2008
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5. Stochastic Variational Approach to Small Atoms and Molecules Coupled to Quantum Field Modes in Cavity QED.

Author

Ahrens, Alexander, Chenhang Huang, Beutel, Matt, Covington, Cody, and Varga, Kálmán

Subjects
*SMALL molecules, *QUANTUM electrodynamics, *WAVE functions, *FUNCTION spaces, *STOCHASTIC processes, *ENERGY function
Abstract

In this work, we present a stochastic variational calculation (SVM) of energies and wave functions of few particle systems coupled to quantum fields in cavity QED. The spatial wave function and the photon spaces are optimized by a random selection process. Using correlated basis functions, the SVM approach solves the problem accurately and opens the way to the same precision that is reached the nonlight coupled quantum systems. Examples for a two-dimensional trion and confined electrons as well as for the He atom and the H2 molecule are presented showing that the light-matter coupling drastically changes the electronic states. [ABSTRACT FROM AUTHOR]

Published
2021
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