Aristotle Papakondylis

Ab initio investigation of the ground state properties of PO, PO+, and PO−

We have computed accurate potential energy curves of the ground states of the PO(X 2Π), PO+(X 1Σ+) and PO−(X 3Σ−) species by multireference configuration interaction and coupled-cluster methods and have obtained accurate spectroscopic constants for each species. We have also determined the effect of core on the properties above and have obtained the PO complete basis set limit by the multireference method for the equilibrium energy, bond distance, dissociation energy, harmonic frequency, and dipole moment.

Ab initio Study of the Electronic Structure of Zinc Oxide and its Ions, ZnO0,±. Ground and Excited States

The species ZnO and ZnO(+/-) have been studied by variational multireference and coupled-cluster [RCCSD(T)] methods employing augmented basis sets of quintuple cardinality. Full potential energy curves are reported for 13, 10, and 2 bound states of ZnO, ZnO(+), and ZnO(-), respectively. All our results are in excellent agreement with existing experimental findings.

Electronic and geometrical structure of the NF2 radical

Abstract Ab initio calculations of equilibrium geometries, excitation energies, dipole moments and charges for the low-lying X 2 B 1 , 1 2 A 1 , 2 2 A 1 , 2 B 2 and 2 A 2 electronic states of the NF 2 radical have been carried out at the RHF/SDCI level, using large basis sets. Our results are in good agreement with experimental data. In addition, a rationalization scheme for the experimental results obtained through UV spectroscopy and photolysis of NF 2 is proposed on the basis of our theoretical results.

Elucidation of the structural characteristics of the isovalent species Li[CO] and Li[CS] by ab anitio calculations

Abstract We have performed ab initio CISD(+ corrections) calculations on the valence isoelectronic molecules Li[CO] and Li[CS] using large basis sets. The LiCo, LiOC, LiCS and LiSC 2 Π states are bound with respect to Li 2 P by 38, 8, 70 and 41 kcal/mol, respectively. With the exception of LiCS 2 Σ + , which presents a shallow minimum of 4kcal/mol, all the relevant 2 Σ + states examined are repulsive. Full potential energy curves are also presented for the most interesting of the states.

A highly accurate first principles determination of the electron affinity of BO(X2Σ+) and binding energy of BO−(X1Σ+)

Highly accurate values of the adiabatic electron affinity (EA) of the ground state (X2Σ+) of the BO molecule, and the dissociation energy (D0) of the anion BO−(X1Σ+), have been determined using the CCSD(T) approach in conjunction with a series of doubly augmented correlation consistent basis sets, d-aug-cc-pVnZ, n=3–6. In addition, the full potential energy curve of BO−(X1Σ+) has been constructed at the multireference configuration interaction, n=5 level. Our final values are, EA(BO)=2.50eV and D0(BO−)=215.7kcal/mol, in excellent agreement with experimental results.

On the electronic structure of the ground (X3Σ−) and some low-lying excited states (A3Π, a1Δ, b1∑+, B3Σ−) of the isovalent species PLi and PNa

Abstract The electronic structure of the isovalent P-Li and P-Na species in their ground X 3 Σ − state and low-lying excited states, A 3 Π, a 1 Δ, b 1 Σ + and B 3 Σ − , has been studied employing CISD, CASSCF and multireference CI techniques. For both molecules and all states studied, we report full potential energy curves, dissociation energies, bond lengths, and spectroscopic constants.

Ab initio study of the ground and several excited states of the NLi system

Abstract Using mainly CASSCF/cc-pVTZ ab initio methods we have computed the ground X 3 Σ − and several excited states of the NLi species. In particular, we calculated full potential energy curves of the X 3 Σ − , 5 Σ − (dissociative), A 3 Π , a 1 Δ , b 1 Σ + , B 3 Σ − , c 1 Π , C 3 Π and d 1 Π states. For sixe of these states the molecular constants ω e , ω e χ e , α e and D e have also been obtained. For the ground X 3 Σ − state a dissociation energy D e = 29.5 kcal mol −1 has been calculated at the MR-CISD level.

Accurate ab Initio Structural Parameters of the Diatomic and Triatomic van der Waals Molecules 11BNg (X2Π, A2Σ+) and 11BNg2 (X̃2B1), Ng = 4He, 20Ne, 40Ar, 84Kr, and 132Xe

The weakly interacting BNg and BNg2 molecular systems, Ng = He, Ne, Ar, Kr, and Xe, have been thoroughly studied through coupled-cluster RCCSD(T) calculations and large correlation consistent basis sets. For the BNg diatomics, the states examined are the X(2)Π and A(2)Σ(+), and the X̃(2)B1 state for the C2v BNg2 triatomics. A series of corrections render our final results reliable, judging as well from the (limited) experimental numbers available. Both BHe and BHe2 are marginally unbound, whereas the attractive interactions of the BNg X(2)Π states, where Ng = Ne, Ar, Kr, and Xe, are D0 = 19.8, 98.2, 141.9, and 209.1 cm(-1), respectively. For the BRn (Rn = radon) species, an estimated value of interaction energy D0 ≈ 280 cm(-1) is obtained by a D0 versus static polarizability (α) extrapolation. Corresponding atomization energies of the BNg2 (X̃(2)B1) molecules are AE0 = 52.0 (BNe2), 263.4 (BAr2), 384.6 (BKr2), and 576.9 (BXe2) cm(-1).

An ab initio study of Li+ …CS, a purely electrostatic system

Abstract The Li + …CS interaction has been computed by SCF and CISD methods, and it was found to be purely electrostatic with a binding energy D e of 33 kcal mol −1 and a bond distance R Li + − C = 2.107 A.