\documentclass[10pt]{letter} \usepackage{UPS_letterhead,xcolor,mhchem,mathpazo,ragged2e} \newcommand{\alert}[1]{\textcolor{red}{#1}} \definecolor{darkgreen}{HTML}{009900} \begin{document} \begin{letter}% {To the Editors of the Journal of Physical Chemistry Letters} \opening{Dear Editors,} \justifying Please find enclosed our manuscript entitled \begin{quote} \textit{``A Density-Based Basis Set Correction For Wave Function Theory''}, \end{quote} which we would like you to consider as a Letter in the \textit{Journal of Physical Chemistry Letters}. This contribution fits nicely in the section \textit{``Spectroscopy and Photochemistry; General theory''}. One of the most fundamental drawbacks of conventional wave function methods is the slow convergence of energies and properties with respect to the one-electron basis set. As proposed by Kutzelnigg more than thirty years ago, one can introduce explicitly the interelectronic distance $r_{12}$ to significantly speed up the convergence. However, significant computational overheads are introduced by the large auxiliary basis used to resolve three- and four-electron integrals. In this Letter, we describe a drastically different approach which combines density-functional theory (DFT) and wave function methods. The present universal, density-based basis set incompleteness correction, which can be applied to any wave function method, relies on short-range correlation density functionals from range-separated DFT to estimate the basis set incompleteness error. Our results clearly demonstrate that the present basis set correction recovers quintuple-$\zeta$ quality atomization and correlation energies with triple-$\zeta$ basis sets for a much cheaper computational cost compared to explicitly-correlated F12 methods. Because of the large impact of our work, we expect it to be of interest to a wide audience within the chemistry community and beyond. We suggest Paola Gori-Giorgi, Tim Gould, David Tew, Emmanuel Fromager and Seiichiro Ten-no as potential referees. This contribution has never been submitted in total nor in parts to any other journal, and has been seen and approved by all authors. We look forward to hearing from you soon. \closing{Sincerely, the authors.} \end{letter} \end{document}