A high-performance Fortran code to calculate spin- and parity-dependent nuclear level densities

Abstract

A high-performance Fortran code is developed to calculate the spin- and parity-dependent shell model nuclear level densities. The algorithm is based on the extension of methods of statistical spectroscopy and implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The proton–neutron formalism is used. We have applied the method for calculating the level densities for a set of nuclei in the sd-, pf-, and pf+g9/2- model spaces. Examples of the calculations for 28Si (in the sd-model space) and 64Ge (in the pf+g9/2-model space) are presented. To illustrate the power of the method we estimate the ground state energy of 64Ge in the larger model space pf+g9/2, which is not accessible to direct shell model diagonalization due to the prohibitively large dimension, by comparing with the nuclear level densities at low excitation energy calculated in the smaller model space pf. Program summaryProgram title: MMCatalogue identifier: AENM_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENM_v1_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 193181No. of bytes in distributed program, including test data, etc.: 1298585Distribution format: tar.gzProgramming language: Fortran 90, MPI.Computer: Any architecture with a Fortran 90 compiler and MPI.Operating system: Linux.RAM: Proportional to the system size, in our examples, up to 75MbClassification: 17.15.External routines: MPICH2 (http://www.mcs.anl.gov/research/projects/mpich2/)Nature of problem:Calculating of the spin- and parity-dependent nuclear level density.Solution method:The algorithm implies exact calculation of the first and second Hamiltonian moments for different configurations at fixed spin and parity. The code is parallelized using the Message Passing Interface and a master-slaves dynamical load-balancing approach.Restrictions:The program uses two-body interaction in a restricted single-level basis. For example, GXPF1A in the pf-valence space.Running time:Depends on the system size and the number of processors used (from 1 min to several hours).