Abstract
Vibrational frequencies were calculated for selenophene, SO, 1,2,5-selenadiazole, SA, tellurophene, TO, and 1,2,5-teliuradiazole, TA, at the B3LYP, MP2 and BF levels of theory. The basis sets used are the CEP-121G, CEP-31G, LanL2DZ, SDDALL and SDD basis sets in addition to the 6-31G(p) and 6-311G(d,p) basis sets for SO and SA. The resulting internal coordinate force fields were scaled using one-scale-factor scaling. The scale factors were varied to minimize the difference between the calculated and experimental vibrational frequencies. Good agreement between the calculated and experimental geometries was obtained. Although the size of the effective core potential (ECF) basis sets is about half or less than those of the non-ECP basis sets, 6-31G(p) and 6-311G(d,p), the obtained average errors and scale factors were comparable to those obtained using the non-ECP basis sets. The lowest average errors were obtained by the SDDALL basis set. The average errors using the MP2 method were unusually high. (C) 2001 Elsevier Science B.V. All rights reserved.