Theory of nuclear quadrupole interactions in aluminum and copper metals in presence of muon |
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Authors: | Schmidt P. C. Coker Ayodele Ray S. N. Sahoo N. Das T. P. |
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Affiliation: | (1) Department of Physics, State University of New York at Albany, 12222 Albany, New York, USA;(2) Present address: Physikalische Chemie III, Technische Hochschule, D-6100 Darmstadt, West Germany;(3) Present address: Federal Ministry of Science and Research, Lagos, Nigeria;(4) Present address: Science Applications Research, 20737 Lanham, MD, USA |
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Abstract: | The electric field gradients at27Al and63Cu nuclei which are nearest neighbors to the muon in the face-centered cubic metals aluminum and copper, with muon at an octahedral interstitial site, are studied. The electron density fluctuations needed for the evaluation of the electronic, or valence, contributions to field gradients are taken from earlier investigations involving the spherical solid approximation. The enhancement factors a that have to be applied to the electric field-gradients obtained from these approximations, due to the departures of the electronic wave-functions from plane-wave character, and the incorporation of antishielding effects, have been obtained for both APW and OPW approaches to the conduction electron wave-functions and good agreement is found between the results by the two approaches. Size effects due to the lattice distortion associated with the presence of the muon are included through actual point ion summations using available calculated displacements of the ions surrounding the muon. The valence contributions are the dominant ones but the size effect contributions are also significant. The net field-gradient obtained for the27Al site is significantly smaller than experiment while that for63Cu is substantially larger than experiment. Possible sources that could lead to better agreement with experiment are discussed and it is concluded that major improvement is needed in the valence effect contributions in both metals. |
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