New approach to the positron distribution in metals and alloys

Search for positron localization near transition-metal solutes of negative effective charge in Ni and Cu

“…Our DB results show no evidence of e+ localization near transition metal solutes of effective negative charge in Cu and Ni of the kind suggested by the Cu alloy ACAR results of Doyama et a1 [4]. Such an effect, if it exists, is smaller than the reproducibility of our measurements.…”

“…Fig. 4 Comparison of our 'spin polarized' DB results to the 2D ACAR results of Genoud et al for a Ni (001) single crystals along the [I001 direction. In both cases data are represented as the difference between 2 spectra acquired with an applied magnetic fieId directed along and opposite to the flight direction of incoming et.…”

“…If volumes of Au atoms in the alloys are greater than that in pure Au, as implied by our observed positive deviation from Vegard's law behaviour [12], this positron affinity is expected to be greater still. Similarly, in an ACAR study of Li(Mg) alloys, Stott and Kubica [4], not able to account theoretically for their results, were led to conclude that et localize in the more attractive Li clusters.…”

Потенциал Ионизации Металлического Кластера, Содержащего Вакансии

“…В [20,21] теория возмущений строилась на базисе ячеечных волновых функций, а ψ c (r) выбиралась в виде плоской волны. В [22] использовалось разложение ψ c (r) по плоским волнам в кристалле. В нашем случае внимание акценти-ровано на граничных условиях для ψ c (r) на поверхности, что приводит к дискретному энергетическому спектру частицы.…”

Calculation of Positron Response from Embedded Nanoparticles

“…Provided that the positron affinity of such particles is lower than that of the matrix, positrons may get trapped in them. This effect was first observed experimentally about 25 years ago [1] and described from the theoretical point of view by several authors [2,3], but until recently [4,5] an effective computational method to determine the positron response from nanoparticles was missing.…”