Multiwfn is able to easily perform QTAIM topology analysis based on .wfn/.molden file generated by ORCA or based on .wfn/.wfx/.fch file generated by Gaussian. If you do not know how to generate these files, please check beginning of Chapter 4 of Multiwfn manual. If you don't know how to do QTAIM topology analysis by Multiwfn, please follow examples in Section 4.2 of Multiwfn manual.In the QTAIM framework, there are several criterions that can judge covalency of a bond, all of them are collectively mentioned in Section 4.A.11 of Multiwfn manual.
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