adapt - solver for differential equations which determine the full set of discretization coefficients in adaptive logarithmic discretization approach in numerical renormalization group nrgchain - tridiagonalisation code for determining the tight-bidning coefficients of the Wilson chain for NRG calculations Copyright (C) 2008, 2009 Rok Zitko adapt solves the differential equations which determine logarithmic discretization coefficients in the form epsilon(x) = g(x) Lambda^(2-x), Epsilon(x) = f(x) Lambda^(2-x), where epsilon(x) are the discretization mesh points and Epsilon(x) the representative energies, while x=j+z is the mesh parameter which combines the discretization interval number j=1,2,3,.. and the twist parameter z in the interval [0:1]. For more details see Rok Zitko: "Adaptive logarithmic discretization for numerical renormalization group methods", Computer Physics Communications (2009). and Rok Zitko, Thomas Pruschke: "Energy resolution and discretization artefacts in the numerical renormalization group", Physical Review B 79, 085106 (2009). nrgchain determines the coefficients xi (hopping constants) and zeta (on-site energies) for a Wilson chain. It takes the output from adapt as its input. 1. Installation Modify "Makefile" if necessary, compile using "make" and copy the resulting executables (adapt, nrgchain) to an appropriate location. The discretization equation solver is written in pure ISO C++ without making use of any external libraries, therefore it should be highly porable. The tridiagonalization code makes use of the GNU MP Bignum library (multiple precision), see http://gmplib.org/. (Tested with GMP version 3.0.5.) 2a. Usage (adapt) Usage: adapt [P|N] [parameter_file] Optional argument P or N specifies whether positive or negative frequency part of the density of states is being discretized [default is "P"]. Argument parameter_file specifies which file contains parameters [default is "param"]. Consult the sample parameter file for description of the parameters. 2b. Usage (nrgchain) Usage: nrgchain [parameter_file] Consult the sample parameter file for description of the parameters. 3. License This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA The full text of the GPL General Public License can be found in file LICENSE. 4. Contact information "adapt" home-page: http://nrgljubljana.ijs.si/adapt/ Rok Zitko "Jozef Stefan" Institute F5 - Condensed matter physics Jamova 39 SI-1000 Ljubljana Slovenia rok.zitko@ijs.si 5. Acknowledgements 'adapt' solver was developed during author's stay at the Institute for theoretical physics, University of Goettingen, Germany. Fruitful discussions with prof. Thomas Pruschke, computer support by GWDG, and support by the German Science Foundation through SFB 602 are acknowledged.