Potential energy surfaces and properties of ICN − and ICN

ICN and ICN − have been studied at the MR‐SO‐CISD level of theory with triple‐zeta basis sets for all three atoms. The potential surfaces for the ground states of ICN and ICN − as well as for the first five excited states of ICN − have been generated from the electronic energies, and properties of these states are described. The minimum energy geometry of ICN − is linear, with a local minimum in the INC − geometry. The zero‐point corrected energy difference between these two isomers is 0.38 eV, and they are separated by a 0.5 eV barrier. The I···CN(COM) equilibrium distances are 3.27 and 3.14 Å in the ICN − and INC − geometries, respectively. These values are 0.6 Å larger than the I···CN distances in the corresponding minima in the ICN potential. Likewise, the zero‐point amplitude of both the I···CN stretch and bend are much larger in ICN − than in ICN. This is captured by the calculated anharmonic fundamental frequencies for ICN − of 70 and 235 cm −1 for the bend and stretch, compared to anharmonic frequencies of 302 and 488 cm −1 for the bend and stretch fundamentals in ICN. The frequencies are lowered further in INC − where the bend and stretch fundamentals have frequencies of 59 and 220 cm −1 . © 2012 Wiley Periodicals, Inc.