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Manuscript Title: NUCPAR: a parity-dependent NBCS formalism at finite nuclear temperature.
Authors: G. Maino, A. Ventura
Program title: NUCPAR
Catalogue identifier: ABQS_v2_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 43(1987)303
Programming language: Fortran.
Computer: IBM 370/168.
Operating system: MVS/SPI.
RAM: 124K words
Word size: 32
Peripherals: disc.
Keywords: Nuclear physics, Structure, Grand canonical, Formalism, Nuclear shell model, Pairing interaction, Finite temperature, Nuclear entropy, Nuclear level density, Parity dependence, Collective model.
Classification: 17.20.

Subprograms used:
Cat Id Title Reference
ABQS_v1_0 NUDENS CPC 29(1983)375

Nature of problem:
NUCPAR is based on a microscopic formalism (Nilsson-Bardeen-Cooper- Schrieffer (BCS) approximation) for the calculation of nuclear thermodynamic functions particularly level densities versus excitation energy, angular momentum and parity. A blocking effect due to unpaired nucleons is intoduced for odd-A and odd-odd nuclei.

Solution method:
A system of nonlinear equations is solved at zero and finite temperature in order to determine pairing correlation functions and chemical potentials. These quantities are thus introduced in grand canonical traces from which thermodynamic functions are derived at given excitation energy and total angular momentum. The ground-state correlation functions (gap parameters), or, alternatively, the pairing strengths for neutrons and protons are taken as input parameters. The parity distribution of excited nuclear states is determined in a simple statistical approach.

Neutron-proton pairing correlations are neglected: therefore, the formalism should be applied to medium-heavy non-magic nuclei where the adopted NBCS approximation is expected to hold. Moreover, factorization of the intrinsic state contribution, the collective enhancement factor and parity distribution in nuclear level densities (see formula (9)) is valid at relatively low excitation energy (U < 30 MeV).

Unusual features:
NUCPAR uses the mathematical subroutine NS01AD from the Harwell subroutine library in order to slove a system of nonlinear equations: the subroutine is included in the deck. Two permanent files, unit 20 and unit 21, containing neutron and proton levels generated in a Nilsson potential, used by the program, are already included in the NUDENS package(Comp. Phys. Commun. 29(1983)375).

Running time:
The execution time is strongly problem-dependent: it is roughly proportional both to the number of blocked single-particle levels and that of the excitation energies considered in the calculation. For instance, the second test run, which includes 8 blocked levels, for protons and neutrons, and 2 excitation energies, requires 1 m 13 sec on IBM 370/168.