Papers by Author: Veena Verma

Abstract: Soon after the discovery of carbon nanotubes, it was realized that the theoretically predicted mechanical properties of these interesting structures could make them ideal for a wealth of technological applications. A number of computer simulation methods applied to their modeling, has led over the past decade to an improved but by no means complete understanding of the mechanics of carbon nanotubes. Tersoff potential has been widely used but it has since been modified many times. The latest is the second-generation reactive empirical bond order potential by Brenner and co workers, which is being used in this work for manipulating these tiny structures. We outline the computational approaches that have been taken. The elastic moduli of armchair, zigzag and chiral nanotubes have been computed. We generate the coordinates of carbon nanotubes of different chirality’s and size. Each and every structure thus generated is allowed to relax till we obtain minima of energy. We then apply the requisite compressions, elongations and twists to the structures and compute the elastic moduli. Young’s modulus is found to be dependent on tube radius for thinner tubes and attains a constant value of the order 1TPa. Our results of Poisson’s ratio and shear modulus are also encouraging and compare well with other theoretical and experimental work.

Abstract: Various gold nanowires with very small cross-sections (few atoms) have been studied using the Gupta potential. Gold nanowire icosa structure is found to be most stable among structures studied. The values of cohesive energy, Young’s modulus and shear modulus have been computed and all the values (except poisson ratio) are more than that of bulk gold. Another striking observation about gold nanostructures is that the Young’s modulus increases with tube radius whereas shear modulus decreases.

Abstract: Based on the assumption that sp3 hybridization is more stable in bulk silicon, this study is a step forward in understanding the structures and mechanical properties of silicon nanotubes (SiNT). Using the well tested form of Tersoff potential we have calculated cohesive energy and other parameters for SiNT of various diameters and chiralities. Using this potential, the results obtained for bulk silicon are satisfactory, so we expect that the same potential would work well with SiNT as well. We calculated Young’ modulus and shear modulus for SiNT. Young’s modulus lies in the range of 100- 200 GPa which is about 10-20 times lower than CNT and shear modulus lies between 200-300 GPa. This work shall motivate further theoretical and experimental work in the field of nanostructures.