Variation of positron annihilation rates in metals

No Abstract

Model for structural defect characterization of metals based on positron beam technique

In this work, a model for the structural characterization of metals usingpositron beam technique was developed and tested. The developed model was tested using experimental data obtained from a positron beam laboratory. The model was based on the Doppler spectrum obtained in the Dopper broadening technique. The model considered specific positron annihilation characteristics in metals. Also, the model considered the properties of positrons as they diffuse through the metals. The Sand W- parameters; types of defects can be simulated from the model for any given incident photon energy and for any metal. The results obtained revealed that the Sparameter, the W-parameter and structural defect simulated using the model is in one to one agreement with the experimental values. The model can be used in place of experiments for the structural characterization of defects in metals

Stabilized jellium model-derived surface stress of metals

No Abstract.Nigerian Journal of Physics Vol. 20 (1) 2008: pp.6-1

Computation of the Structure Factor of Some Transition Liquid Metals

Applying the solution of the Percus-Yevic equation to a one component hard sphere system and using the  recently developed potential for liquid transition liquid metals, the structure factor of transition liquid metals were computed. The peak height and peak position of the structure factor of the liquid metals were studied. The results obtained were compared with available experimental values. The results obtained revealed that the structure factor of liquid transition metals computed using the harmer potential were in better agreement with experimental values and the use of the potential reproduced the structure factor, peak position and peak height of the structure factor of some transition liquid metals.Keywords: liquid metals, structure factor, potential, peak position and peak heightJournal of the Nigerian Association of Mathematical Physics, Volume 19 (November, 2011), pp 527 – 53

Bulk modulus of metals according to structureless pseudopotential model

The method for calculating the bulk modulus of metals based on thestructureless pseudopotential model was fully developed. The developed method was used to calculate the bulk modulus and kinetic energy contribution to the bulk modulus of 46 elemental metals. The results obtained were compared with experimental values and their variation with electron density parameter was studied. The results obtained revealed that the calculated and experimental bulk modulus of metals varies in thesame manner with the electron density parameter. The calculated bulk modulus of metals was in very good agreement with experimental values for the simple metals in the low-density limit and the agreement between the calculated and experimental bulk modulus of metals decreases towards the high-density limit where we have the transition and the noble metals. The results further revealed that the kinetic energy contributes significantly to the bulk modulus of metals and varies in the same mannerwith the electron density parameter as the bulk modulus. The agreement between the calculated and experimental bulk modulus of metals shows that the structuresless pseudopotential model is promising for predicting metallic properties

Work function of elemental metals and its face dependence: Stabilized Jellium approach

The stabilizing potentials and work functions of elemental metals were calculated for the flat surface, the (111), (100) and (110) faces using the stabilized jellium model. The calculated work functions were compared with experimental values and calculated values obtained using the ab initio method. The stabilizing potentials for the different faces of the metals revealed that the less densely packed faces require higher potential for stabilization in the stabilized jellium model. The calculated work functions for the flat surface of the metals were in perfect agreement with experimental values for metals in the low-density limit and the agreement with experimental values decreased towards the high-density limit. The calculated work functions for the body centred cubic metals were in good agreement with experimental values. The calculated work function for the hexagonal close packed metals were in fairly good agreement with experimental values while the degree of agreement with experimental values was least for face centred cubic metals. The work functions of metals calculated in this work revealed that the more closely packed faces have higher work functions. The results obtained in this work revealed that the stabilized jellium model could be used to predict fairly well the work function of metals and calculate other metallic properties. JONAMP Vol. 11 2007: pp. 445-45

Effects of Screening on the Thermal Resistivity And Compressibility Ratio of Metals

Models for computing thermal resistivity, compressibility ratio, and screening parameter of metals was developed and used to study the effects of screening on the thermal resistivity and compressibility ratio of metals. The results obtained revealed that the thermal resistivity of metals increases with an increase in the electron gas parameter. It also increases with an increase in the screening parameter showing that the screening in metals affects the thermal resistivity of metals. The results obtained further revealed that thermal resistivity of metals increases with increase in temperature. On the compressibility ratio, the results obtained shows that the compressibility ratio decreases with an increase in the electron gas parameter. Also, the compressibility ratio decreases with an increase in the screening parameter.Keywords: Thermal resistivity, compressibility ratio, screening, screening parameter and metalsJournal of the Nigerian Association of Mathematical Physics, Volume 19 (November, 2011), pp 519 – 52

Effects of deformation on the energies of metals

In this work, a model for computing the correlation, binding and cohesive energy of deformed and undeformed metals was developed based on the structureless pseudopotential formalism. Based on the developed model, the correlation, binding and cohesive energy of metals were computed and studied. Also, the computed binding and cohesive energy of metals were compared with available experimental values. The results obtained showed that correlation energy increases with increase in electron density parameter, also, increase in deformation increases the correlation energy. The computed binding energy and cohesive energy of metals were in good agreement with experimental values. The results obtained further showed that deformation causes a decrease in the binding energy of metals and it does not cause a significant change in the cohesive energy of metals, although transition metals have high values of cohesive energy compared to alkaline and simple metals.Keywords: Metals, pseudopotential model,cohesive, binding and correlation energy