ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
In a recently published report on the time-of-flight mass spectrometry studies and ab initio RHF/3-21G calculations of the CnN− clusters (n=1 to 13), Wang, Huang, Liu, and Zhang claimed that all the CnN− clusters (n=1 to 13) should be linear chains. In the present work, we report the new results obtained from a series of ab initio calculations on the ground states of the CnN− cluster anions. The results calculated at different approximation levels reveal that the geometries of the CnN− determined at the levels without using the polarization functions is qualitatively incorrect, and that the diffuse functions of the two atoms at the two end points of the CnN− chains and the higher-order electron correlation are important in evaluating the vertical electron detachment energies (VDEs) of the CnN− anions. It is concluded from the calculated results that for the singlet ground states, only the linear structures of CN−, C2N−, C3N−, and C5N− are stable, and the linear structures of the other CnN− (n=4 and 6 to 13) are not at the local minima on the potential energy surfaces. The VDEs and fragmentation energies of CnN− (n=1 to 7) in their ground states are evaluated with the MP4SDTQ method at the MP2 geometry using 6-31G(d) except for two end atoms of each chain, to which a set of diffuse sp functions are augmented. The fragmentation energies are also evaluated with the QCISD(T) method using the same basis to verify the convergence of the perturbational results. The calculated VDEs and fragmentation energies all show that the CnN− clusters with odd n are more stable than those with even n, which is consistent with the observed even–odd alternation of the TOF signal intensities. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.471638
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