Determination of equations of state for nano-structured amorphous metals by molecular dynamics method

Equations of state are used to calculate the thermodynamics parameters of matters. Instead of analytical calculations, the molecular dynamics simulation methods as alternative approach can be used to calculate equations of state. In this thesis, the isotherm and isobar curves for nickel and copper metals have been obtained by using molecular dynamics simulations. Voter-Chen and Johnson type of embedded atom methods have been used for modeling the physical interactions between atoms of nickel and copper, respectively. The molecular dynamics method have been carried out in two different ways. In the first, which is called bulk-structured, periodic boundary conditions were acted on the molecular dynamics cell while in the second, called nano-structured, periodic boundary conditions were not acted. In the both applications, thermodynamics properties of the amorphous model systems obtained by rapid quench technique applied in an another molecular dynamics simulation have been investigated. The thermodynamics properties of nano structures and its amorphous phases consisting of different number of atoms varying from 108 to 6912 have been investigated. The variation of enthalpy and potential energy with the number of atoms have been analyzed with respect to each other. V=f(P,T) relations and its surface graphs have been produced from the obtained results. The results have been discussed by comparing the calculated results with those obtained from Vinet, Birch-Murnaghan and Davydov equations of state. It has been concluded that the results from molecular dynamics simulations are in consistent with those from the analytical expressions. In addition, a different method to calculate the volume of nano-structured amorphous systems have been developed and its results are in good agreement with experimental data. It has been determined by this method that the nano-structured systems are more densely formed as compared to both bulk crystals and amorphous structures. Keywords: Molecular dynamics simulation, equation of state, amorphous structures, nano structures, thermodynamic parameters.