Grand canonical electronic density-functional theory: Algorithms and applications to electrochemistry.
First-principles calculations combining density-functional theory and continuum solvation models enable realistic theoretical modeling and design of electrochemical systems. When a reaction proceeds in such systems, the number of electrons in the portion of the system treated quantum mechanically changes continuously, with a balancing charge appearing in the continuum electrolyte. A grand-canonical ensemble of electrons at a chemical potential set by the electrode potential is therefore the ideal description of such systems that directly mimics the experimental condition. We present two distinct algorithms: a self-consistent field method and a direct variational free energy minimization method using auxiliary Hamiltonians (GC-AuxH), to solve the Kohn-Sham equations of electronic density-functional theory directly in the grand canonical ensemble at fixed potential. Both methods substantially improve performance compared to a sequence of conventional fixed-number calculations targeting the desired potential, with the GC-AuxH method additionally exhibiting reliable and smooth exponential convergence of the grand free energy. Finally, we apply grand-canonical density-functional theory to the under-potential deposition of copper on platinum from chloride-containing electrolytes and show that chloride desorption, not partial copper monolayer formation, is responsible for the second voltammetric peak.
Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, USA.
Ravishankar
0000000206254592
R
Sundararaman
Joint Center for Artificial Photosynthesis, California Institute of Technology, Pasadena, California 91125, USA.
William A
0000000300975716
WA
Goddard
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA.
Tomas A
TA
Arias