Best optimized one-electron wave-functions. IV. Ionization energies of atoms

On the basis of the previously described method for optimization of one-electron wave-functions, a simple procedure has been developed to determine the ionization energies in atomic cases. The procedure gives all the ionization energies at once with relatively high accuracy. This is possible due to optimal distribution of the total electron charge between the individual spin-orbitals.     

Best optimized one-electron wave-functions. III. Direct examination of optimization effectiveness

The effectiveness of the recently developed method for optimization of one-electron wave-functions is directly examined by means of a simple procedure. By means of the same procedure the dependence of electron correlation on the nuclear charge and on the number of electrons is also investigated.     

Best optimized one-electron wave functions. I. The general procedure of optimization

A new effective semiempirical method of optimization of one-electron wave-functions has been proposed without a necessity to determine any exact many-electron wave-function. The method designed for LCAO MO calculations is based on a concept of interacting quasi-particles and on nonorthogonal spin-orbitals. “Mixing” of the pure single-particle wave-functions is optimized by means of the procedure which requires only one empirical parameter for each considered state of a whole system. The procedure results in optimal distribution of total electron charge between the individual spin-orbitals. The general method has been illustrated with calculations for the ground state of lithium atom.     

Ab initio Valence Bond Study on AB-type Molecules,A Description for XH(X=L,Be,B,C,N,O,F) and XF(X=Li,Be,B)

Ab initio valence bond method is employed to quantitatively study the concepts of ionic resonance energy and ionicity of a chemical bond in the cases of hydrides XH(X=Li,Be,B,C,N,O,F) and fluorides XF(X=Li,Be,B),By establishing the relationship between resonance and stability,and comparing the calculated ionicities with Pauling‘s earlier estimations in the above diatomic molecules,the merits of Pauling‘s classical resonance theory were demonstrated at the ab initio level.     

Electron localizability indicators ELI–D and ELIA for highly correlated wavefunctions of homonuclear dimers. I. Li2, Be2, B2, and C2

Electron localizability indicators based on the parallel‐spin electron pair density (ELI–D) and the antiparallel‐spin electron pair density (ELIA) are studied for the correlated ground‐state wavefunctions of Li₂, Be₂, B₂, and C₂ diatomic molecules. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two functionals. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for Li₂, B₂, and C₂ the reliable topology of ELI–D is obtained only at the correlated level of theory. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010     

Isoelectronic reagents. II. Standard formation enthalpies of phenyl and pfluorophenyl iodine dichlorides

The formation heats ΔH^o_fPhICl₂(c) = 21.7 kJ mol^?1 and ΔH^o_fpFC₆H₄ICl₂(c) = ?173.0 kJ mol^?1 were determined by reaction of iodides with excess chlorine in methyl cyanide. These heats are used to show:(i) that thermal or photo-decompositions of aryl iodine dichlorides are kinetically controlled,(ii) the greater halogenating ability of aryl iodine dichlorides than Ph₃ACl₂ (A = P, As, Sb) compounds, and(iii) the weakening of halogenating ability with phenylation.     

A neutron activation analysis method for the determination of Be,Li, B,F, and Pb

A neutron activation analysis procedure that utilizes reactor pulsing, rapid sample transfer and a Cerenkov counter for the determination of Be, Li, B, and F via very short-lived radioisotopic indicators is shown to give analytical sensitivities for these elements of 15μg, 0.0008μg, 1.1μg, and 0.83μg, respectively. Use of a NaI(Tl) counter coupled to the same system enables the detection of 0.4μg of Pb via 0.8 second^207mPb.     

Stability,continuity, and symmetry of variational wave-functions

Interrelations between the local and the global aspects of the stability, continuity, and symmetry properties of variational wave-functions are discussed. The spherical limit of one-electron diatomic molecules and the Hartree–Fock approximation of the ground state of the two-electron atom are shown to exhibit the various concepts involved in an ab initio, yet sufficiently simple, manner.     

Re‐examination of the C6Li6 Structure: To Be,or not To Be Symmetric

The potential energy surface of C₆Li₆ was re‐examined and a new non‐symmetric global minimum was found. The new structure can be described as three C₂^2? fragments strongly aggregated through lithium bridges. At high temperatures, fluxionality is perceived instead of dissociation. At 600 and 900 K, the BOMD simulations show that the lithium mobility is high, indicating that the cluster behaves in a liquid‐like manner (BOMD=Born–Oppenheimer molecular dynamics).     

Theoretical Study on the Structure and Stability of Si4X（X=Li, Be, B, C, N, O, F） Clusters

1 INTRODUCTION Silicon is an important kind of semiconductormaterial having been used to produce many sorts ofapparatus, digital and linear integrated circuit andLarge Scale Integrated circuit (LSI), and its clustershave drawn many scientists’ atten…     

Ab initio calculations of electron-spin magnetic moments for Li,Be and B hydrides inX 2∑+ states

Electron-spin magnetic moments, in the form ofg-shifts, have been computed at the ROHF level for theX ²∑⁺ states of LiH⁺, BeH²⁺, LiH^?, BeH and BH⁺. A perturbative approach, complete to second-order in appropriate Breit-Pauli operators, has been used. Retention of two-centre integrals has proven vital. First-order terms are important, especially in describing the negativeg _∥ shifts observed experimentally in²∑⁺ molecules. The relativistic mass correction dominates in first-order, except for LiH^? where the two-electron spin-Zeeman gauge correction supersedes. Second-order terms contribute negatively, and only to the Δg _⊥ component. Along the isoelectronic series LiH^? → BeH → BH⁺, the magnitude of Δg _⊥ increases due to the dependence of spin-orbit coupling on nuclear charge. The relation ofg-shifts to electronic structure and bonding is explored.     

Polarization consistent basis sets. 4: the elements He, Li, Be, B, Ne, Na, Mg, Al, and Ar

Polarization consistent basis sets, optimized for density functional calculations, are proposed for the elements He, Li, Be, B, Ne, Na, Mg, Al, and Ar. The basis sets for He, B, Ne, Al, and Ar are assigned based on the previously proposed basis sets for H, C-F, and Si-Ar. The basis sets for Li, Be, Na, and Mg are defined based on energetic analysis along the lines used in previous work and the performance for molecular systems. The performance for atomization energies is comparable to those for systems composed of the elements H, C-F, and Si-Ar.     

Angle and bond-length dependent C6 coefficients for H2 interacting with H,Li, Be and rare gas atoms

Summary Accurate new C₆ dispersion energy coefficients, and their dependence on the diatom orientation and bond length, are calculated for molecular hydrogen interacting with an atom of H, Li, Be, He, Ne, Ar, Kr or Xe. They are generated from accurateab initio pseudo dipole oscillator strength distributions (DOSD) for H₂, H, He and Be, and reliable semiempirical ones for Li, Ne, Ar, Kr and Xe. Compact power series expansions for the diatom bond-length dependence of these coefficients, suitable for incorporation into representations of full potential energy surfaces for these systems, are determined and assessed.     

Properties of nearly one-electron molecules. II. Application to the Rydberg spectrum of CaF

The ab initio K matrix method described in the preceding paper (Part I) is applied to the Rydberg electronic structure of calcium monofluoride. The spectroscopic quantum defects for the 2Sigma+, 2Pi, 2Delta, and 2Phi states of CaF are computed using the effective potential of Arif et al. [M. Arif, Ch. Jungen, and A. L. Roche, J. Chem. Phys. 106, 4102 (1997)]. Satisfactory agreement with the experimental values is obtained. The eigenquantum defects obtained from the reaction matrix for the CaF++e- system are found to be strongly energy dependent. The analysis shows that the main features of the energy-dependent structure in the eigenphases are a consequence of a broad molecular shape resonance. Partial-l (orbital angular momentum) characters of two interacting collision eigenchannels vary rapidly as a function of increasing collision energy. This prominent variation leads to interference structure in the intensities for transitions into the ionization continuum, manifesting nodal points in the total ionization cross section in the continuum above the shape resonance. The usefulness of this structure in the ionization cross section as a direct probe of the l-character of the bound state is discussed. In addition, ab initio results for the photoelectron angular distribution and the anisotropy parameter are presented. These computed results are susceptible to direct experimental verification.     

Theoretical study on the structures and electron spectra of C60M12 (M=Li,Na, Be)

Intermediate neglect of differential overlap (INDO) method was used to study the structures and the electronic spectra of C₆₀M₁₂ (M=Li, Na, Be). The calculations indicate that in the minimal energy configuration of C₆₀M₁₂ (M=Li, Na) the C₆₀ cage still retains I_h symmetry and the 12 Li or Na atoms are symmetrically located above the pentagons of the C₆₀ cage, whereas the difference between the double and single bonds has been significantly reduced. In contrast, because six electrons are filled in the fivefold‐degenerated h_g orbital of C₆₀, the C_s structure of C₆₀Be₁₂ has illustrated the occurrence of Jahn‐Teller distortion. Based on the optimized geometries, the electronic absorption spectra were calculated and the nature of red shift was discussed. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 505–509, 1999     

Small elemental clusters. I. The structures of Be2, Be3, Be4, and Be5

The geometries and energies of beryllium clusters up to Be₅ are examined using ab initio molecular orbital theory. Allowances are made for electron correlation with Møller—Plesset perturbation theory to fourth order. Correlation is found to have a dramatic effect on the relative energies of the several structures examined for Be₄ and Be₅. Furthermore, the effect of d-type basis functions on the correlation energy results in an increased binding energy for the clusters. Be₂ is only weakly bound. For Be₃, the best estimate of the binding energy is 6 kcal/mole for the singlet equilateral triangle. Be₄ is tetrahedral in its ground state and the estimated binding is 56 kcal/mole. The best structure for Be₅ is a singlet trigonal bipyramid, and the binding energy is 88 kcal/mole at the highest level of theory used.