Theoretical studies of XCnX (X = O, S, Se; n=1-8): structures, spectroscopic properties, and dissociation energies
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The structural, electronic and spectroscopic properties of a series of small neutral polycumulenic clusters XCnX (n = 1 - 8; X = 0, S, Se) have been investigated by means of ab initio methods and density functional theory. The theoretical results revealed the following: (i) CnO2, CnS2 and CnSe2 clusters possess symmetric linear structures and exhibit drastic odd/even alternation in some structural parameters, such as bond lengths, rotational constants and so on; (ii) The energies differences of adjacent clusters also exhibit drastic odd/even parity, that is, DeltaE(n) Of CnX2 with odd n is lower than that of even-numbered ones, indicating that the former is more stable; (iii) The above-mentioned alternation effect reduces with the growth of the carbon chain and, meanwhile, is weakened following the sequence: CnO2 > CnS2 > CnSe2. (iv) These molecules are in favor of losing CX unit, among the eight possible dissociation channels that lose C, C-2, C-3, CX, C2X2, CX2, X or X-2 fragments. (C) 2002 Elsevier Science B.V. All rights reserved.