EFFECTS OF LINEAR DEFORMATION ON SOME PROPERTIES OF SELECTED METALS

Abstract

In this work, a model for computing the electron density parameter, Fermi wave – vector, Fermi energy, correlation energy, binding energy, cohesive energy, surface energy, surface stress, chemical potential, strain energy density, relaxation time, Fermi velocity, Fermi temperature, mean free path, electrical conductivity and the wavelength of electron at Fermi surface of deformed and undeformed metals was developed based on the structureless pseudopotential model. This study generalized the work of Kiejna and Pogosov (2000) due to the shortcomings of the electron density parameter of deformed metals. They failed to account for metal dilation by assuming a constant value for the Poisson ratio of metals which leads to neglect of the uniaxial strain in their computation. This causes the electron density parameter for both deformed and undeformed metals to be equal. This work presents a generalized method to determine the electron density parameter for deformed metals and some other metallic properties studied. A computer programming language was developed and used in the computation of the above named metallic properties. The results obtained revealed that the electron density parameter of metals increases as deformation increases. The Fermi energy, Fermi wave – vector and chemical potential of the metals decreases with increase in deformation. The computed Fermi energy of undeformed metals is in good agreement with experimental values. The chemical potential exhibits a trend that suggests dependence on some other properties. The variation of chemical potential with deformation is least compared to other electronic properties of metals investigated. The results in the study also showed that correlation energy increases with increase in electron density parameter and an increase in deformation decreases 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 has no significant change in the cohesive energy of metals, although transition metals have high values of cohesive energy compared to alkaline and simple metals. The results obtained revealed that deformation causes a reduction of surface energy and this reduction is more pronounced in simple and alkaline metals. For surface metals, tensile stress is present in most metallic surfaces. Deformation causes a decrease in surface stress for most metals. The reverse was however the case for chromium. Furthermore, the result obtained revealed that the higher the effect of deformation on the strain energy density of metals the lower the density of the valence electron and the lower the energy stored per unit volume in metals, the less the effect of deformation. The mean free path and Fermi velocity of metals decreases with an increase in deformation. The relaxation time and electrical conductivity of all the metals investigated decreases as deformation increases. The Fermi temperature of metals decreases as deformation increases with the metals in the high density region having high Fermi temperature while metals in the low density region have low Fermi temperature. The wavelength of electron at Fermi level increases as deformation increases.