Wenli Zou

On the Covalent Character of Rare Gas Bonding Interactions: A New Kind of Weak Interaction

At the averaged quadratic coupled-cluster (AQCC) level, a number of selected rare gas (Rg) containing systems have been studied using the quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO), and several other analysis methods. According to the criteria for a covalent bond, most of the Rg-M (Rg = He, Ne, Ar, Kr, Xe; M = Be, Cu, Ag, Au, Pt) bonds in this study are assigned to weak interactions instead of van der Walls or covalent ones. Our results indicate that the rare gas bond is a new kind of weak interaction, like the hydrogen bond for example.

Symmetry breaking in the ground state of BNB: a high level multireference study.

A series of multireference approaches based on the SA-CASSCF wave function, i.e., CASPT2, MRCI, MRCI + Q, and MRAQCC with single- or multireference states, have been employed to investigate the symmetry breaking effect in the ground state X (2)Sigma(u)(+) of the triatomic BNB radical. We found that the mixing of the reference states contributes significantly to the dynamical correlation energy, which strongly affects the geometry of the ground state. Our results show that BNB in its ground state has a linear noncentrosymmetric structure with two equivalent global minima of the adiabatic potential energy surface and, respectively, two oppositely directed dipole moments of about 2 D. The barrier between the minima is about 20 cm(-1). The origin of the double-minimum potential in the ground state of BNB is explained as due to the pseudo-Jahn-Teller effect involving vibronic interaction with the first excited state A (2)Sigma(g)(+) via the asymmetric stretching vibrations.

He@Mo6Cl8F6: A Stable Complex of Helium

The electronic structure and chemical stability of the endo helium cluster, He@Mo(6)Cl(8)F(6), were investigated carefully by using density function theory. The results show that the cluster is significantly different from typical van der Waals systems: the bond distance between helium and molybdenum is only about 1.89 A. Moreover, the bonding analysis clearly reveals considerable charge and bond order on the helium atom and bond order for He-Mo. The dissociation of He@Mo(6)Cl(8)F(6) to He + Mo(6)Cl(8)F(6) is prohibited by a barrier of 0.86 eV (19.8 kcal/mol), indicating that the cluster is chemically stable. However, no covalent He-Mo bonding was found so it is an analogue of He@adam. Comparison was also made with the isoelectronic system of [Mo(6)Cl(8)F(6)](2-).

Theoretical Study on the Low-Lying Electronic States of NiH and NiAt

The low‐lying electronic states of NiH and NiAt are investigated by using multireference second‐order perturbation theory with relativistic effects taken into account. The potential energy curves as well as the corresponding spectroscopic constants are reported. The results are grossly in good agreement with the available experimental data and should thus be very useful for guiding future experimental measurements. A cross comparison with other nickel monohalides NiX (X = F, Cl, Br, and I) reveals that the change in the spin–orbit splittings when going from lighter to heavier ligands results more from the state interaction than from the relativistic effects of the ligands.

Do non-centro-symmetric linear X-Y-X molecules exist? The case for the (I)Π2u state of CuCl2

The potential energy surface of the low-lying excited state (I)(2)Pi(u) of CuCl(2) is constructed by using the ionization potential equation-of-motion coupled-cluster method and also the RASPT2 method with a large active space of 21 electrons in 17 orbitals to improve the results. It is found by the multiconfiguration calculation that this state has a barrier of 53 cm(-1) between two equivalent minima in which the linear molecule has a dipole moment. In our computations artifactual symmetry breaking is carefully avoided. Further refinement, including consideration of interaction between the two excited (2)Pi states, yields a somewhat higher barrier between 100 and 500 cm(-1). The mechanism of formation of the double-minimum potential is explained by the pseudo-Jahn-Teller effect theory. Computed spectroscopic constants are in good agreement with experimental ones.

Time-dependent DFT study on the electronic states of BBr

Abstract Using time-dependent density functional theory (TDDFT), the vertical excitation energies of BBr molecule are calculated, and the RPBE functional which has the optimum results is selected to compute the potential energy curves of the ground, the 12 valence and the 4 Rydberg excited states of BBr. The equilibrium bond distances, the vibrational frequencies and the excitation energies of nine bound states are obtained. In order to improve the theoretical results, the spin–orbital coupling effects are computed for the ground and the first excited states. Finally, the transition properties are predicted.

Ab initio study on the ground and low-lying excited states of GaH

A multireference configuration interaction (MRCI) study has been carried out on GaH. Potential energy curves and spectroscopic constants of the X 1 R þþ ,a 3 P0� ;0þ;1;2 ,A 1 P1 and a Rydberg state of 1 R þ (II) are obtained. The observed open-structure absorption bands of GaH in the region 41 650–46 300 cm � 1 can be ascribed to the transitions from this Rydberg state at about 45 000 cm � 1 to the ground state. Breit–Pauli operator is used for spin–orbit coupling effect calculations. Four X components of the bound a 3 P0� ;0þ;1;2 state are calculated for the first time. The transition properties of the excited states, including the transition dipole moments, the radiative lifetimes and the Franck–Condon factors, are predicted. 2003 Elsevier Science B.V. All rights reserved.

DFT study on the ground and the first excited states of gallium monohalides

The spectroscopic constants (SCs) of the ground states and the first excited states of gallium monohalide diatomic molecules are carried out, by using the density functional theory (DFT) with different local density approximation (LDA) and general gradient approximations (GGA), for the first time. The results obtained by different LDAs and GGAs are compared with the observed values and the theoretical results; and also compared to the results calculated with and without a combined scalar and zero order regular approximation (ZORA) relativistic corrections, respectively, showing that DFT with appropriate LDAs and GGAs are fairly successful for dealing with the ground and first excited states of these molecules with heavy elements. Furthermore, the scalar and ZORA relativistic correction are suggested as good approximate approaches.

Ab initio calculations on the ground and low-lying excited states of InCl

All-electron relativistic calculations have been performed on the low-lying electronic states of InCl by using the internally contracted multireference singles and doubles configuration interaction with the Davidson correction method. The potential energy curves and the spectroscopic constants are obtained. The C 1Π1 state has also been studied by using other internally contracted multireference methods, and it is found that the spectroscopic constants can be well reproduced by the multireference average quadratic coupled cluster method. Moreover, the essentials that affect the spectroscopic properties of the C 1Π1 state are discussed. Besides the X 1Σ+, 3Π0−, A 3Π0+, B 3Π1, 3Π2, and C 1Π1 states, some valence excited states with shallow minima close to each other and four Rydberg states are also obtained. With the aid of the theoretical results, some experimental weak bands are reanalyzed: it is proved that the so-called “D state” is not a single state in fact, but a set of closely spaced states with sha...

Theoretical study of C1Π–X1Σ+ transition of InCl

Abstract Using coupled-cluster with single and double substitutions (CCSD) and based on the density functional theory (DFT), geometry optimization calculations have been performed for the ground state of InCl, and the spectroscopic constants are obtained. The potential energy curve, the spectroscopic constants and the radiative lifetimes for the vibrational levels of the C 1 Π state are also computed by the use of CCSD, the results being in accordance with the experimental values, and showing that the C 1 Π system is a quasi-bound state with a shallow well. Considering the effects of avoided crossing and barrier penetration, the maximal vibrational quantum number of the C 1 Π state should not be more than 4.