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Manuscript Title: A program to calculate magnetic form factors for transition metal
systems. | ||

Authors: L.A. Barnes, G.S. Chandler, B.N. Figgis, D.C. Khan | ||

Program title: MAGFAC | ||

Catalogue identifier: AABR_v1_0Distribution format: gz | ||

Journal reference: Comput. Phys. Commun. 36(1985)373 | ||

Programming language: Fortran. | ||

Computer: CYBER CDC720. | ||

RAM: 170K words | ||

Keywords: Solid state physics, Crystal field, Neutron scattering, Form factor magnetic, Spin, Orbital, Spherical, Aspherical, Density magnetization. | ||

Classification: 7.3. | ||

Nature of problem:MAGFAC calculates magnetic form factors for a transition metal ion under the influence of a crystal field. This can be defined, in the formalism of Trammell, as the expectation value of the operator representing the magnetic interaction of the neutron with the ion at a particular lattice site. The program calculates each Cartesian component of the form factor, as well as its magnitude. The spherical, dipole approximation and free atom form factors are also calculated. | ||

Solution method:The wavefunction for the ion is expressed as a sum of n-electron or n- hole Slater determinants of single particle wvefunctions. The program determines the non-zero matrix elements of the interaction operator, via the Condon-Shortley rules, for the input wavefinction. The spin and orbital operator contributions are evaluated using standard angular momenta relations. These non-zero matrix elements are expanded in terms of spherical harmonics, Ylm, Condon-Shortley coefficients, C**L(l,m;l', m'), and the radial integrals <jL>and <gL>. The form factors are thus calculated for any reflaection (h,k,l) in the Cartesian system determined by the user. | ||

Restrictions:MAGFAC is restricted to Hartree-Fock level crystal field wavefunctions for transition metal systems with a partially filled 3d shell. The structure of the program enables the case of 4f electrons to be incorporated in a straightforward manner. The present dimensions restrict the input wavefunction to 50 determinants, with 5 electrons or holes maximum for d electrons. The radial function is represented by a basis set of up to 5 Slater Type Orbitals, and up to 350 reflections are allowed. | ||

Running time:This varies widely from problem to problem. A typical run with 20 three-electron determinants and 340 reflections was accomplished in 16 s on the Cyber CDC720. The test cases here all took <= 0.6 s. Compilation time is ~12 s. |

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