First Principle Simulations of Current Flow in Inorganic Molecules: Polyoxometalates (POMs)

In this work we present a simulation study of current flow in inorganic molecular metal oxide clusters known as polyoxometalates (POMs). The simulations are carried out by using combination of the density functional theory (DFT) and non-equilibrium Green's function (NEGF) methods. To investigate the current flow in POMs, we investigate two possible ways to place the POM cluster between two gold (Au) electrodes - vertical and horizontal. Our results show that the position of the POM molecule and the contact between the molecule and the Au electrodes determines the current flow. Overall, the vertical configuration of the molecule between the two Au electrodes shows better current flow in comparison to the horizontal configuration. In this work we also establish a link between the underlying electronic structure and transmission spectra and conductance.

I. Introduction

In recent years interest in electronic, magnetic and optical structures and devices based on inorganic, organic, hybrid and nano-materials has increased significantly. Polyoxometalates (POMs) are molecules that contain metal and oxygen atoms. They are highly ordered clusters and they exist as several structures [1]. Among them, the most notable structures are the Keggin anion ([XM₁₂O₄₀]^q-) and the Wells-Dawson anion ([X₂M₁₈O₆₂]^q-) that can be defined as ‘electron sponges’. These molecular clusters could be used to develop new types of data storage devices [2] and various other applications [3]. For detailed information on polyoxometalates, we suggest readers consult some of the recent reviews [4], [5].