Predicting the thermodynamic properties of gold nanoparticles using different force fields.

摘要

The objective of this research was to learn how to predict the thermodynamic properties of gold nanoparticles using computational tools. The lowest energy structures of gold nanoparticles of various sizes were determined and thermodynamic properties such as the free energy (F), internal energy (U), entropy (S), and specific heat (Cv) of the gold nanoparticles were investigated using a fully-atomistic Monte Carlo simulation method that utilizes a modified Wang-Landau algorithm. Eight well-known force fields for metallic systems were employed to model gold nanoparticles: the Lennard-Jones potential (LJ), the Lennard-Jones potential with Heinz's parameterization (LJH), the Gupta potential, the Sutton-Chen potential (SC), the Sutton-Chen potential with Pawluk's parameterization for small clusters (SCP), the Quantum Sutton-Chen potential (Q-SC), the Embedded Atom Method (EAM) by Cai and Ye, and the empirical potential for gold proposed by Olivier and coworkers (POT). Subsequently, we explored the accuracy of each force field in the description of the thermodynamic behavior of gold nanoparticles.;The thermodynamic properties of gold nanoparticles were computed from the Density of States which was obtained as a result of the Monte Carlo simulation. Afterwards, the melting point of gold nanoparticles was determined from the behavior of the calculated thermodynamic properties and was compared with theory, experimental observations and other simulation results. The force fields employed predicted melting points of gold nanoparticles over a wide range of temperatures. A thorough comparison with the available experimental observations showed that the Quantum Sutton-Chen potential (Q-SC) correctly described the melting behavior of gold nanoparticles with sizes smaller than 1.3 nanometers.