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Theoretical Study of Positronic Atoms with Adiabatic Separation of Positronic Motion

100%

Strasburger K., Wołcyrz M.

Acta Physica Polonica A

2008

vol. 113

issue 5

1533-1542

A modified adiabatic approximation, with the positron treated as a light nucleus and its charge included only partially in the electronic Hamiltonian, was applied to compute the energies and properties of bound states of lithium positride, positronic beryllium and positronic magnesium. The electronic Schrödinger equation was solved with the configuration interaction method. No bound state was obtained for lithium positride, while the dissociation energies of positronic beryllium and positronic magnesium were underestimated by 2.6 and 7 millihartrees, respectively. Consequences for the applicability of the adiabatic approximation to describe positronic systems are discussed.

Copper Deficiency - a Crystallochemical Nature of Ce-Doped Gd_2CuO_4 Phase. Part II

81%

Horyń R., Bukowska E., Sikora A., Wołcyrz M.

Acta Physica Polonica A

2004

vol. 106

issue 5

733-738

Two samples of nominal composition Gd_{1.80}Ce_{0.15}CuO_{4.0} and Gd_{1.85}Ce_{0.15}CuO_{4.075} were subjected for a long-term treatment in air at 1100°C, comprised with a precise control of their weights vs. time of the treatment applied. The gravimetric analysis and the iodometric titration, both showed a deficiency on Cu-site, steadily increasing vs. time with a slight tendency to a saturation. The X-ray analysis of the resulting products showed that even after 272 h of sintering, the samples remained single phase of the "214" structure type. Refinement of their crystal structures as well as density measurements, both allowed confirming Cu deficient structure constitution of these samples. Results of dc-magnetization measurements, performed prior to reduction of the sample's overall oxygen content, did not show any sign of superconductivity down to 4.2 K. These preliminary results indicate that copper deficiency, developing during synthesis, may occur to be a decisive factor for the reported lack of superconductivity in Ce-doped Gd_2CuO_4 phase. Oxygen content reduction and further tests on the samples obtained are in progress.

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2 Acta Physica Polonica A

1 2008

1 2004

2 Wołcyrz M.

1 Bukowska E.

1 Horyń R.

1 Sikora A.

1 Strasburger K.

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Theoretical Study of Positronic Atoms with Adiabatic Separation of Positronic Motion

Copper Deficiency - a Crystallochemical Nature of Ce-Doped Gd_2CuO_4 Phase. Part II