Multiwfn

Developed by Dr. Tian Lu (Beijing Kein Research Center for Natural Sciences), Multiwfn has become the Swiss Army knife of wavefunction analysis—a powerful, flexible, and surprisingly accessible tool that has changed how computational chemists understand their molecules. At its core, Multiwfn (short for "Multifunctional Wavefunction Analyzer") is a program that takes the output of a quantum chemical calculation—a file containing the molecular orbitals, electron density, and other properties—and transforms it into chemical insight.

It proves that in science, the best tools are not always the ones with the biggest price tags or the flashiest interfaces. Sometimes, they are the ones built by a dedicated researcher who simply wanted to understand the wavefunction a little better. Download Multiwfn from the Kein Research Center website. Start with the provided example files (e.g., examples\exaf... ). Generate a .fchk file from Gaussian (or a .molden from ORCA), point Multiwfn to it, and type 0 for the main menu. Then, begin exploring. multiwfn

In the early days of quantum chemistry, after a long computation finished, researchers were often left with a cryptic output file and a single, stark number: the total energy. Was the molecule stable? Possibly. But why ? What electronic forces held it together? Where were the reactive spots? Developed by Dr