Basis set and correlation effects in the calculation of accurate gas phase dimerization energies of two M+2 to give M2+4 (M = S, Se)
✍ Scribed by Jenkins, H. Donald B.; Jitariu, Luminita C.; Krossing, Ingo; Passmore, Jack; Suontamo, Reijo
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 418 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
The dimerization energies of two M + 2 to give M 2+ 4 (M = S, Se) were calculated. They depend strongly on the size of the basis set and the correlation method used (ranging from 217 to 522 kJ/mol, M = S) and, therefore, a systematic study of basis set and correlation effects was performed [MP2, MP3, MP4(SDQ), CCSD, CCSD(T)]. The introduction of a second set of polarising d-functions caused a significant reduction of the dimerization energies, but neither of the above limits is reached by the MPn (n = 2, 3, 4) theory, even with the largest basis sets [cc-pVQZ]. However, convergence was achieved by CCSD(T), compound methods or hybrid HF/DFT calculations employing flexible basis sets [e.g., CCSD(T)/cc-pV5Z, CBS-Q or B3PW91/6-311+G(3df)] and revealed an average dimerization energy of 261 (199) kJ/mol for sulfur (selenium), r H 298 (2S + 2 → S 2+ 4 ) is 257 kJ/mol. In the selenium system the dependence on basis set and correlated method was less pronounced.