A Study of Computer-Based Simulations for Nano-Systems and their types

In most of the cases, the experimental study of Nanotechnology involves high cost for Laboratory set-up and the experimentation processes were also slow. So, one cannot rely on experimental nanotechnology alone. As such, the Computer-Based molecular simulations and modeling are one of the foundations of computational nanotechnology. The computer based modeling and simulations were also referred as computational experimentations. In real experiments, the investigator doesn’t have full control over the experiment. But, in Computational experimentation the investigator have full control over the experiment. The accuracy of such Computational nano-technology based experiment generally depends on the accuracy of the following things: Intermolecular interaction, Numerical models and Simulation schemes used. Once the accuracy of the Computational Scheme is guaranteed one can use that to investigate various nonlinear interactions whose results are completely unexpected and unforeseen. Apart from it, numerical modeling and computer based simulations also help to understand the theoretical part of the nano-science involved in the nano-system. They allow us to develop useful analytic and predictive models. In this paper, a brief study of Computer-BasedSimulation techniques as well as some Experimental result obtained using it were given. INTRODUCTION The computer based simulation techniques [1] are widely used for computational nano-technology. The frequently used simulation approaches are Monte Carlo (MC) and Molecular Dynamics (MD) methods. The other various simulation methods come from these two basic methods. Apart from it, the optimization techniques were also needed in MC and MD. The computerbased simulation methods, developed for nanosystems, generally consist of a computational procedure performed of few atoms or molecules confined in a small geometrical space. This geometrical space in which the simulation is performed is termed as cell. In the subsequent section, a brief classification of simulation methods based on Accuracy, Computational Time etc were given. After it, classifications of optimizations in molecular simulations were discussed. In next section after it, we have discussed the result of computer -based simulation. MONTE CARLO AND MOLECULAR DYNAMICS SIMULATION METHODS [2, 3, 6] The two basic used simulation approaches are Monte Carlo (MC) and Molecular Dynamics (MD) methods. All the other various simulation methods come from these two basic methods. A brief over-view with areas of application of the both are discussed below. These concepts are essentially required to understand the methodology of classification of Computer-Based Simulation methods based on accuracy and time-complexity. MC method uses random numbers to perform calculations. There are many areas of application of MC Methods including nano-material. Some important areas where we apply MC method are: (i) Estimation of large-dimensional integrals (ii) Generating thermodynamic ensembles in order to compute thermal averages of physical equilibrium quantities of interest and simulation of non-equilibrium phenomena such as growth and (ii) Computation of distribution functions out of equilibrium known as Kinetic Monte Carlo [5]. MD deals with predicting the trajectories of atoms subject to their mutual interactions and eventually an external potential. Some important areas of application of MD are: (i) Computation of transport properties such as response functions, viscosity, elastic moduli and thermal conductivity (ii) Thermodynamic properties such as total energy and heat capacity and (iii) Dynamical properties such as phonon spectra. CLASSIFICATION OF SIMULATION METHODS BASED ON ACCURACY AND COMPUTATIONAL TIME Computer based methods used for simulation of various properties of nano scale systems differ in their level of accuracy and time-complexity to perform such calculations. Based on it, the required time scale for these methods can be from tens of picoseconds (e.g. ab initio MD calculations) to few microseconds or more