Multicomponent density functional theory: Including the density gradient in the electron-proton correlation functional for hydrogen and deuterium
Tao Zhen, Yang Yang, and Sharon Hammes-Schiffer. Multicomponent Density Functional Theory: Including the Density Gradient in the Electron-Proton Correlation Functional for Hydrogen and Deuterium. Vol. 151, no. 12, J. Chem. Phys., 2019, p. 124102.