Spin transport in the phenalenyl radical throughout molecular dynamics trajectories

Abstract

The phenalenyl family of radicals has previously been identified as either possessing high spin filter efficiency (SFE) or excellent conductance, with these behaviors being tunable by the application of bias voltage. However, the persistence of these traits in the presence of thermally-induced structural fluctuations has yet to be determined. In this study, we employ a combination of ab initio molecular dynamics (AIMD) and the non-equilibrium Green's function technique combined with density functional theory (NEGF-DFT) to show how spin and charge transport behaviors evolve in a phenalenyl (PLY) molecular junction under thermal motion. To this end, we performed 5000 fs AIMD trajectories on Au-PLY-Au molecular junctions at temperatures of 300 K, 500 K, and 700 K, calculating charge and spin transport properties every 100 fs over these simulations. Remarkably, the molecule remained bonded to the Au electrodes at temperatures up to 700 K. Similarly, the SFE of the junction was stable against fluctuations caused by thermal-induced motion, with the SFE remaining above 80% for the majority of the three trajectories. Although there were a few instances of SFE dropping below 80%, strong SFE was quickly recovered within 200 fs. Additionally, the conductance of the molecular junction broadly increased with the temperature of the AIMD trajectory, with the 700 K trajectory producing the highest set of conductance values. Through the combination of AIMD and NEGF-DFT techniques, we show the robustness of spin filtering behavior in the PLY against thermally-induced structural changes in molecular junctions and that higher temperature can result in higher conducting configurations.