
%0 Journal Article
%A Petrie, Simon 
%T Circumstellar Calcium Chemistry
%J Australian Journal of Chemistry
%D 2004/01/06
%V 57
%N 1
%P 67-76
%K Ca &#8212; quantum chemical calculations &#8212; organometallic compounds &#8212; cyanopolyynes &#8212; stars
%R https://doi.org/10.1071/CH03173
%U https://www.publish.csiro.au/paper/CH03173 
%X High-level ab initio calculations are used to explore several aspects of calcium chemistry of direct relevance to formation and reaction of calcium-containing molecules in circumstellar envelopes. Counterpoise-corrected G2 and G2(MP2) calculations have been used to determine the bond dissociation energies (BDEs) of Ca&plus;/NC2n&plus;1H complexes (n = 0, 1, 2); these complexes, and CaNC7H&plus;, are also assessed through counterpoise-corrected MP2(thaw)/6-311 &plus; G(3df,2p) calculations. The relative energies of isomers of the feasible Ca(CN), Ca(C3N), and Ca(C5N) products (which may arise from dissociative recombination of the Ca&plus;/NC2n&plus;1H complexes) are obtained from G2 and G2(MP2) calculations; these calculations also permit evaluation of the thermochemistry of the dissociative recombination reactions in question. Thermochemical data are presented for a possible loss mechanism for calcium-containing neutrals by reaction with molecular ions in circumstellar envelopes. Finally, we provide an empirical assessment of the prospects for detecting the Ca(CN), Ca(C3N), and Ca(C5N) radicals within circumstellar environments. 
