Electron Transport Through Molecules: Self-consistent and Non-self-consistent Approaches

TL;DR

This paper introduces a self-consistent method based on density functional theory and nonequilibrium Green functions for electron transport in molecular devices, along with an efficient non-self-consistent approximation validated on metallic chains.

Contribution

It develops a computationally efficient non-self-consistent approach for electron transport that approximates the voltage drop, validated against self-consistent calculations.

Findings

Non-self-consistent method yields quantitatively good I-V curves.

Approach effectively models different voltage drop scenarios.

Method reduces computational cost significantly.

Abstract

A self-consistent method for calculating electron transport through a molecular device is proposed. It is based on density functional theory electronic structure calculations under periodic boundary conditions and implemented in the framework of the nonequilibrium Green function approach. To avoid the substantial computational cost in finding the I-V characteristic of large systems, we also develop an approximate but much more efficient non-self-consistent method. Here the change in effective potential in the device region caused by a bias is approximated by the main features of the voltage drop. As applications, the I-V curves of a carbon chain and an aluminum chain sandwiched between two aluminum electrodes are calculated -- two systems in which the voltage drops very differently. By comparing to the self-consistent results, we show that this non-self-consistent approach works well and can give quantitatively good results.