**1. NAME AND TITLE**

ICAR: A Code For Combinatorial Calculation of Level Densities

**2. CONTRIBUTOR**

ENEA, Bologna, Italy, through IAEA, Vienna, through NEA Data Bank, France.

**3. CODING LANGUAGE AND COMPUTER**

Fortran 77; IBM PC/AT.

**4. NATURE OF PROBLEM SOLVED**

ICAR performs state and level density calculations for a specified type of nucleon. Calculations
can be carried out in terms of the free gas model or in the frame of the BCS formalism to account for
the pairing interaction.

**5. METHOD OF SOLUTION**

The code starts by calculating properties of the ground state, such as the correlation function,
chemical potential, total energy and condensation energy. Next all possible configurations of n
excitons within the adopted orbitals are generated by means of a combination enumeration algorithm.

**6. RESTRICTIONS OR LIMITATIONS**

None noted.

**7. TYPICAL RUNNING TIME**

The sample input problem (test case 5) was run at NEA Data Bank on an IBM PC/AT with a math
coprocessor. The problem took about 30 minutes.

**8. COMPUTER HARDWARE REQUIREMENTS**

ICAR runs on an IBM PC/AT with a math coprocessor.

**9. COMPUTER SOFTWARE REQUIREMENTS**

The code was written in Fortran 77. The NEA Data Bank used the RM/Fortran compiler, version
2.4 under the MS-DOS 3.20 operating system.

**10. REFERENCES**

M. Herman, G. Retto, "Chain Of Codes for the Combinatorial Calculation of Level Densities," ISSN/0393-6333; IAEA 0974/01 (July 6, 1988).

M. Herman, "Workshop on Applied Nuclear Theory and Nuclear Model Calculations for Nuclear
Technology Applications," SMR/284-9 (February-March 1988).

**11. CONTENTS OF CODE PACKAGE**

Included are the referenced document and one DS/HD (1.2 MB) 5.25-inch diskette.

**12. DATE OF ABSTRACT**

November 1990.

**KEYWORDS:** MICROCOMPUTER; NUCLEAR MODELS