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1

Ab Initio Study of AuTe2 Cluster

Su Rong Q. M., Liu F. M.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 2

285-292

EN

The geometries of the lowest-lying isomers of small AuTe2 cluster are determined through the MP2 method. The aspect of gold-telluride and telluride-telluride interaction, the electron correlation and relativistic effects on geometry and stability were investigated at the different theoretical levels of electron correlation. The results show that the electron correlation and relativistic effects are responsible not only for telluride-telluride attraction but also for additional gold-telluride interaction. Both effects are essential for determining the geometry and relative stability of coin age metal telluride compound AuTe2 cluster.

2

Electron correlation effects on geometries and 19F shieldings of fluorobenzenes

Webb G. A., Karadakov P. B., England J. A.

Bulletin of the Polish Academy of Sciences. Chemistry

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2000

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Vol. 48, No. 1

101-112

EN

In order to include the effects of electron correlation in ab initio molecu- lar orbital calculations it is necessary to go beyond the single determinant Hartree-Fock (HF) level of theory. In the present investigation the influences of both dynamic and nondynamic correlation effects on the optimised geometries and F nuclear shielding calculations of the twelve fluorobenzenes are reported. The non-dynamic electron correlation effects are represented by complete-active space self-consistent field (CASSCF) calculations. Second- and fourth-order Moller-Plesset (MP2 and MP4) calculations are used to describe the dynamic electron correlation effects. Some density-functional (DFT) results are also reported which do not distinguish between dynamic and non-dynamic electron correlation. Following the correlated geometry optimisations F nuclear shielding calculations were performed using the gauge-included atomic orbitals (GIAO) procedure, these were undertaken with wavefunctions which include various levels of electron correlation including HF, CASSCF and MP2. For the calculations of the optimised geometries, and some of the nuclear shieldings the 6-31G** basis set is used whereas the locally-dense [6-31G** on C and H and 6-311++G(2d,2p) on F] set is used for some of the shielding calculations. A comparison of the results of HF shielding calculations using other basis sets is included. Comparison of the calculated geometry and shielding results with relevant, reported, experimental data is made

3

The ground state of (He-H-He)(+) from correlated ab initio calculations

Komasa J., Rychlewski J.

Polish Journal of Chemistry

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1998

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Vol. 72, nr 7S

1353-1360

EN

He2H(+) ion in its ground state is studied by means of ab initio methods taking into account the electron correlation. Geometry optimization at the CCSD(T)/cc-pV5Z level of theory has been performed and the potential energy hypersurface scan is presented. The optimum conformation is linear and symmetric with the proton at the He-He midpoint and the He-H distance equal to 1.75 bohr. Stabilization energy with respect to the He2H(+) --- HeH(+) + He dissociation channel has been computed. Additionally, a single point variational calculations with the use of the Exponentially Correlated Gaussian wave functions have been performed. They supply an upper bound to both the total electronic energy (-5.903505 hartree) and the stabilization energy (-13.224 kcal/mol). A comparison of the results from both the perturbational coupled cluster and variational methods is presented.