Sachin .; Brijesh Kumar Pandey; Ratan Lal Jaiswal
Abstract
In the present study, a well-established relation between the band gap of low dimensional solid and its cohesive energy has been used to calculate the band gap variation at nano level. The different thermodynamical models proposed for the cohesive energy do not consider the unsaturated bonds of surface ...
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In the present study, a well-established relation between the band gap of low dimensional solid and its cohesive energy has been used to calculate the band gap variation at nano level. The different thermodynamical models proposed for the cohesive energy do not consider the unsaturated bonds of surface atoms, the shape of the nanoparticle and the packing density of the corresponding crystal simultaneously. Extending the bond energy model, a simple theoretical model for the cohesive energy has been proposed which incorporate all the above-mentioned properties simultaneously and hence getting a more comprehensive relation between the band gap and the characteristics of the nanoparticle. We have computed bandgap of compound semiconducting nanosolids ZnE and CdE, (E=S, Se, Te) in different shapes. It is found that band gap expands as the particle size decreases and the shape deviates more from spherical one. A close agreement between our calculated results and the available experimental data validates the present theoretical model. The present expression of Band gap of Nanosolids is potentially applicable for those materials whose experimental data are not available.
Ratan Lal Jaiswal; Brijesh Kumar Pandey
Abstract
Variation of thermomagnetic properties of nanoparticles are the matter of great debate. To develop a suitable model for the study of magnetic properties, the size and shape dependent magnetic properties such as Curie temperature (TC), Neel temperature (TN) and magnetization (MS) of magnetic nanoparticles ...
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Variation of thermomagnetic properties of nanoparticles are the matter of great debate. To develop a suitable model for the study of magnetic properties, the size and shape dependent magnetic properties such as Curie temperature (TC), Neel temperature (TN) and magnetization (MS) of magnetic nanoparticles (Fe, Ni, Co, Fe3O4, NiO, CoO, CuO, Ho and CoFe2O4) have been studied. In the present work, bond energy model has been used with the concept of dangling bond and its effect on the surface of nanoparticles. It is observed that the introduction of packing fraction of materials to this model supports the experimental facts. The obtained results have been explained by considering the concept of dangling bond at the surface of nanoparticle and packing fraction of crystal. It is observed that these magnetic properties decrease with reducing size of nanoparticles and the available experimental data are in good agreement with present theoretical model. The validity of present model encourages us to predict the behaviour of thermomagnetic properties of other nanoparticles.
