Propargyl radical: an electron localization function study

Bonding in the C3H3 radical has been determined using the topological analy sis of the electron localization function (ELF) calculated with various wav efunctions (HF, LSDA, MP?, CASSCF, QCISD, BLYP, B3LYP). Not only is ELF ind ependent of quantum chemical approximation, but also produced topologically equivalent molecular partitions. The ELF partition of space into localizat ion domains provides an objective characterization of bonding in C3H3, supp orting a resonance description of almost equal contributions of propargyl a nd allenyl forms. Moreover, it explains the reported difference between the frequencies of the in-plane and out-of-plane bending modes (<C(2)C(3)H(3)) arising from the topology of the C(2)C(3) bonding region. (C) 1999 Elsevie r Science B.V. All rights reserved.