Current-Voltage Curves for Molecular Junctions Computed Using All-Electron Basis Sets

TL;DR

This paper demonstrates that all-electron basis set calculations for molecular junction I-V curves are comparable to ECP methods, with reduced computational effort using a hybrid scheme and core state approximations.

Contribution

Introduces a hybrid integration scheme for all-electron calculations that maintains accuracy while reducing computational costs in molecular junction simulations.

Findings

All-electron results closely match ECP results up to 2 V bias.

The hybrid scheme significantly reduces computational effort.

Diffuse functions are essential for basis set completeness.

Abstract

We present current-voltage (I-V) curves computed using all-electron basis sets on the conducting molecule. The all-electron results are very similar to previous results obtained using effective core potentials (ECP). A hybrid integration scheme is used that keeps the all-electron calculations cost competitive with respect to the ECP calculations. By neglecting the coupling of states to the contacts below a fixed energy cutoff, the density matrix for the core electrons can be evaluated analytically. The full density matrix is formed by adding this core contribution to the valence part that is evaluated numerically. Expanding the definition of the core in the all-electron calculations significantly reduces the computational effort and, up to biases of about 2 V, the results are very similar to those obtained using more rigorous approaches. The convergence of the I-V curves and transmission coefficients with respect to basis set is discussed. The addition of diffuse functions is critical in approaching basis set completeness.