DFT and QM/MM simulations of the electrochemical interface

Understanding the interface between electrolytes and electrified metallic surfaces is essential for many technological applications, but still poses important scientific challenges. Computer simulations could contribute to solve these challenges, but to simulate accurately and realistically the interface is not an easy task. For Density Functional Theory (DFT) simulations, in particular, the complexity of the interface, the presence of the electrode's potential, and the very long time scales involved, represent serious obstacles. We have recently proposed a method, based on Non-Equillibrium Green's Functions, to perform DFT simulations in the presence of externally imposed electrode potentials, and have implemented this NEGF-DFT methodology [2] in the SIESTA code [3]. I will show how this approach has been successfully used to study the interaction of water with an electrified gold electrode. Although successful in describing the effect of the electrified surface, the method still suffers the drawback of only being able to access times scales of up to tenths of nanometers, too short to fully describe the response of the electrolyte to the applied potential. I will describe some multiscale approaches which we are exploring to reach longer time scales in our DFT simulations. One of them is a hybrid QM/MM approach which, linked to the NEGF-DFT methodology, allows to reach longer simulation times. We will describe the application of these methods in different problems, including the use of organic compounds to inhibit corrosion in metals [4,5,6]. 

References:
[1] Ordejón et al., Bulletin APS, https://meetings.aps.org/Meeting/MAR23/Session/S60.2 (2023); Bulletin APS, https://meetings.aps.org/Meeting/MAR21/Session/X19.1 (2021)
[2] Brandbyge et al., Phys. Rev. B 65, 165401 (2002); Papior et al., Comp Physics Comm. 212, 8 (2017).
[3] Soler et al., J. Phys.: Cond. Mat., 14, 2745 (2002);  García et al, J. Chem. Phys. 152, 204108 (2020).
[4] Castillo et al., npj Materials Degradation (in press)
[5] Deng et al., Mol. Syst. Des. Eng. 9, 29 (2024)
[6] Castillo et al., in preparation.