Start
May 29, 2014 - 17:00
End
May 29, 2014 - 18:00
Venue
Creativity Hall (Room 118) Chemical Engineering
Event Type
Speaker
Sanjib Sikder Ph.D. student Chemical Engineering IITB
Title
Study of Compound Semiconductors Using Molecular Simulations
Abstract: Compound semiconductor alloys constitute an important class of materials with unique opto-electronic properties which find use in many devices such as those used for display or data storage applications. The work consists of three sections employing Monte Carlo (MC) simulation techniques; first one is a study of structural properties of III-V binary alloys second one is a study of miscibility characteristics of III-V and II-VI ternary alloys and the third one is a study of structural properties of III-V and II-VI ternary alloys. The structural properties of the III-V binary alloys (modelled using the Abell-Tersoff potential) have been investigated using the standard Metropolis MC algorithm in the isothermal isobaric ensemble at 300 K and 1 bar. Having established by comparison with experimental and molecular dynamics (MD) simulation generated data from literature that MC techniques can be applied to predict structural properties of the binary III-V alloys with reasonable accuracy we studied the miscibility characteristics and structural properties of the III-V and II-VI ternary alloys. The miscibility diagrams (temperature as a function of composition at 1 bar) of these ternary alloys (modelled using the valence force field (VFF) potential) determined in the work of this thesis using the transition matrix Monte Carlo (TMMC) method in the isothermal isobaric semigrand (N P T ξ2 ) ensemble are found to be asymmetric. MC simulations have been performed in the isothermal isobaric semigrand (N P T ξ2 ) ensemble to determine the lattice constants nearest neighbour and next nearest neighbour bond lengths and bond angles at 300 K and 1 bar. We have analyzed the variation of these properties with composition using Z-plots and bond-type dependent topological rigidity parameters. Kelires and his co-workers had indicated the shortcomings of the MD technique to predict the properties of the group IV alloys and have pioneered the use of MC which does not have limitations of MD. We have extended the use of MC to study the ternary alloys especially to determine the miscibility diagrams without assuming the regular solution theory.