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"NRG Ljubljana" - open source numerical renormalization group code

"NRG Ljubljana" is a general-purpose flexible framework for performing large scale numerical renormalization group (NRG) calculations for quantum impurity problems. It is highly extensible without sacrificing numerical efficiency. I advocate open access to knowledge in science. The "NRG Ljubljana" framework is thus licenced under the General public licence (GPL). You are entitled to run the program, for any desired purpose, study how the program works and modify it, redistribute copies and improve the program. I would, however, appreciate citations to Phys. Rev. B 79, 085106 (2009) and DOI if you make use of the results produced with this code. The PRB paper introduced a new discretization scheme for NRG that led way to much improved results at high frequencies and high temperatures, while the Zenodo DOI is assigned to a recent (2021) version of the "NRG Ljubljana" code.


Obtaining the code

Download the current version of "NRG Ljubljana" from github (external link, zip file)

The package should work unmodified on any modern Unix (MacOS is fine) or Linux distribution with a good standards-compliant C++ compiler (C++17 required, mostly tested with GCC 9.3.0). It requires BLAS/LAPACK libraries, Boost, GNU Scientific Library (GSL), GNU Multiple Precision library (GMP), HDF5 (optionally) and Wolfram Mathematica. Mathematica is only required for the initialization of the problem (basis construction, diagonalisation of the initial Hamiltonian, transformations of the operator matrices, etc.); if Mathematica is not present, the code will still work with manually generated input files.

Legacy versions are documented here.

Examples and documentation

Library of examples (2019)

NRG UFU/2019 Advanced Studies School, in Feb 2019 in Uberlândia, Brazil.

A Mathematica implementation of the NRG method is also available. It illustrates the main ideas of the algorithm on the single-impurity Anderson model using simple Mathematica notebook interface. It calculates the thermodynamic quantities and the expectation values of arbitrary local operators.

Last modified: 29. 5. 2021 Request more information Rok Zitko's home page