ABSTRACT
When Pratim Chattaraj asked me to provide some kind of ‘‘foreword’’ to this book, my first reaction was ‘‘no,’’ since everyone knows that the past is not so important in science and that one person’s recollections often are faulty. What we had here was just a long-laboring quantum chemist with a rigorous training in classical Gibbsian chemical thermodynamics, always enchanted with the chemical potential. So when quantum chemistry was suddenly confronted with the density functional theory (DFT), I was ready and happy to plunge into work with DFT, the chemical potential again taking a central role. To say a little more, below is reproduced a short piece which I provided for a 2003 Springer book entitled Walter Kohn (two photographs which were in the original are omitted). What this contains is the story of how DFT came into chemistry proper, broadening computational chemistry and enlightening chemical concepts both old and new. Concepts are what this volume is mainly about: conceptual DFT.
