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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. The package is freely available under the General Public licence (GPL).


Obtaining the code

I advocate open access to knowledge in science. The "Ljubljana NRG" 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.

Download the current version ( of "NRG Ljubljana"

The package should work unmodified on any modern Linux distribution and, with some tweaking, on any Unix or Unix-like operating system with a good standards-compliant C++ compiler. (Mac OS X is fine.) It requires BLAS/LAPACK libraries, Boost, GNU Scientific Library (GSL), GNU Multiple Precision library (GMP), 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.).

By far the easiest way to compile NRG Ljubljana is using the EasyBuild framework. Using EasyBuild, NRG Ljubljana can be fully built (including taking care of all dependencies except Mathematica) using the command eb --from-pr 4651.

Examples and documentation

Examples and tutorials

NRG tutorials at SISSA, June 2013: slides (ppt, pdf), tutorials (cca. 50 MB), solutions to some exercices (cca. 8 MB)

Reference manual: (version from May 30, 2013)

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: 31. 5. 2017 Request more information Rok Zitko's home page