The paper describing the interaction region indicator (IRI) function proposed by me has been finally published, see

Tian Lu, Qinxue Chen, Interaction Region Indicator (IRI): A Simple Real Space Function Clearly Revealing Both Chemical Bonds and Weak Interactions, Chemistry—Methods, 1, 231-239 (2021) DOI: 10.1002/cmtd.202100007 https://chemistry-europe.onlinelibrary. … .202100007

This is an open-access paper. A detailed document showing how to perform IRI analysis in Multiwfn can be downloaded here: //www.umsyar.com/multiwfn/res/IRI_tutorial.zip

IRI is a new important real space function that able to clearly revealing both chemical bonds and weak interactions, see large number of examples in the paper. IRI has much better graphical effect than DORI, and the definition is much simpler. IRI is also able to nicely elucidate variation of electronic structure and weak interactions in a whole chemical process, relevant animation files are provided in supplemental information of the paper. In addition, a variant named IRI-pi is also proposed, it is able to vividly exhibit pi interaction and distinguish pi interaction strength.