ACCURATE PREDICTIONS OF ROTATIONAL CONSTANTS FOR LINEAR CARBON CHAIN MOLECULES
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Date
1990
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Ohio State University
Abstract
Rotational constants via ab initio theory have typically been calculated in the recent literature by using double-zeta plus polarization (DZP) basis sets, and including electron correlation to third order in the many-body perturbation scheme (MP3). An empirical correction factor, usually obtained from studies on species isoelectronic to the one of interest, is then applied to bring the predicted rotational constant closer to the experimental value. It is shown here that using triple-zeta basis sets which include two sets of polarization functions (TZ2P), but including electron correlation to only second order (MP2) gives rotational constants which are in closer agreement to experiment without resort to empirical scaling. Furthermore, since algorithms for analytically computing energy gradients at MP2 are routinely available, much less effort is required. MP2/TZ2P rotational constants are compared to MP3/DZP and MP2/DZP rotational constants for $C_{3}O, C_{2}S$, and $C_{3}S$. MP2/TZ2P rotational constants for other linear carbon chain molecules are presented
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Author Institution: Department of Chemistry, John Carroll University