Use of Improved Orbitals for CCSD(T) Calculations for Predicting Heats of Formation of Group IV and Group VI Metal Oxide Monomers and Dimers and UCl6

详细信息    查看全文

• 作者：Zongtang Fang ; Zachary Lee ; Kirk A. Peterson ; David A. Dixon
• 刊名：Journal of Chemical Theory and Computation
• 出版年：2016
• 出版时间：August 9, 2016
• 年：2016
• 卷：12
• 期：8
• 页码：3583-3592
• 全文大小：346K
• 年卷期：0
• ISSN：1549-9626

文摘

The prediction of the heats of formation of group IV and group VI metal oxide monomers and dimers with the coupled cluster CCSD(T) method has been improved by using Kohn–Sham density functional theory (DFT) and Brueckner orbitals for the initial wave function. The valence and core–valence contributions to the total atomization energies for the CrO₃ monomer and dimer are predicted to be significantly larger than when using the Hartree–Fock (HF) orbitals. The predicted heat of formation of CrO₃ with CCSD(T)/PW91 is consistent with previous calculations including high-order corrections beyond CCSD(T) and agrees well with the experiment. The improved heats of formation with the DFT and Brueckner orbitals are due to these orbitals being closer to the actual orbitals. Pure DFT functionals perform slightly better than the hybrid B3LYP functional due to the presence of exact exchange in the hybrid functional. Comparable heats of formation for TiO₂ and the second- and the third-row group IV and group VI metal oxides are predicted well using either the DFT PW91 orbitals, Brueckner orbitals, or HF orbitals. The normalized clustering energies for the dimers are consistent with our previous work except for a larger value predicted for Cr₂O₆. The prediction of the reaction energy for UF₆ + 3Cl₂ → UCl₆ + 3F₂ was significantly improved with the use of DFT or Brueckner orbitals as compared to HF orbitals.