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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

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.

News

14.9.2023: An implementation of a new self-energy trick (F. B. Kugler) is available on github: donrolih/sigma-trick-reference.
15.1.2022: Job opportunity: Funding is available for further development of the NRG code and scientific research based on its applications. See the advertisemenet for the opening.
29.5.2021: A snapshot of NRG Ljubljana has been published on Zenodo and it has been assigned a DOI. You can now cite NRG Ljubljana as
Zitko, Rok. (2021, May 29). NRG Ljubljana (Version 8f90ac4). Zenodo. http://doi.org/10.5281/zenodo.4841076
24.2.2020: NRG Ljubljana source code is now hosted on github. The code now uses a new CMake-based build system and has been partly rewritten in a modern C++ style (C++17 required now, C++20 will be required in near future).
24.2.2020: An interface between NRG Ljubljana and TRIQS is available on github, and the documentation with examples is here. By providing both C++ and Python bindings, this interface is very convenient for both experienced users and beginners alike. In addition, this package does not require Mathematica at run-time.

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: 14. 9. 2023 Request more information Rok Zitko's home page