Electron Affinities Of Atoms Research Articles

The use of the k nearest neighbor method to classify the representative elements

The use of Statistics in Chemistry has grown significantly with advances in computation. Nowadays it is easier to deal with a large data set and extract relevant chemical information. This paper describes the use of k nearest neighbor method to classify the representative elements as metal or nonmetal according to their periodic properties: atomic radius, ionization energy, electron affinity and electronegativity. The method requires a very simple mathematical background and can be easily performed and understood. The algorithm classifies an object into a distinct class when there are two or more groups of objects of known class and takes into account the distances among the objects. The pedagogical objective is to present an interdisciplinary activity in which Statistics can be used to make comparisons in Chemistry.

Structure and Properties of Polyfluoride Fn(-) Clusters (n = 3-29).

The electronic and geometrical structures of the neutral Fn and singly negatively charged Fn(-) polyfluorides (n = 3-29) are studied using three levels of theory: density functional theory (DFT) with generalized gradient approximation, hybrid Hartree-Fock-DFT, and hybrid HF-DFT with long-range corrections. For n > 4, each polyfluoride possesses a number of states with different geometries that are closely spaced in total energy. The geometrical structures of the lowest total energy states follow different patterns for the even-n and odd-n Fn(-) anion branches with a preference for higher symmetry geometries. The largest F29(-) anion considered is found to possess Oh symmetry. All the anions beginning with F3(-) are found to possess adiabatic and vertical electron detachment energies exceeding the electron affinities of halogen atoms and are therefore superhalogen anions. Electron affinities, energies of formation, and binding energies show oscillatory behavior as functions of the number n of fluorine atoms. The neutral Fn species are found to be barely stable and are bound by polarization forces. The Fn(-) anions, on the contrary, are quite stable toward the loss of F, F(-), and F2(-), but not to the loss of F2.

A new equation for calculation of chemical hardness of groups and molecules

Chemical hardness is considered to be a useful theoretical descriptor in many experimental and theoretical studies and this concept has several important applications in chemistry. In this study, an equation for atomic hardness is proposed. Following the equation for atomic hardness which is based on charges, ionisation energies and electron affinities of atoms, a new equation is obtained for the calculation of the chemical hardness of groups and molecules using the atomic hardness equation and the principle of chemical hardness equalisation. Molecular chemical hardness may be calculated using α and β parameters of atoms in a molecule or group through the use of the obtained molecular hardness equation. Furthermore, the advantage of this equation over other equations in the literature is that using this equation the chemical hardness of the charged groups and molecules can also be calculated. Besides, the relationship between molecular hardness and charge of molecule is examined using the results obtained from the new molecular hardness equation, and the partial charges of atoms in molecules are calculated with the help of derived equations.

A new equation based on ionization energies and electron affinities of atoms for calculating of group electronegativity

In particular, in organic chemistry, the electronegativity of functional groups are taken into consideration significantly to predict reaction mechanism and to explain inductive effects of functional groups. In the present study, considering the relationship with charge of the electronic energy for atoms, Sanderson’s electronegativity equalization principle and Density Functional Theory (DFT), we have obtained a new equation by which group electronegativity can be calculated from ionization energies (I) and electron affinities (A) of atoms that constitute the group, where the results obtained were compared with equation of Sanderson who proposed that group electronegativity is the geometric mean of atomic electronegativities. For a large number of groups, it was found to be a very close agreement with a standard deviation of 0.12. The advantage of the present equation is that it can be used for ionic groups. In addition, the derived equation can be used to calculate Mulliken and Pauling electronegativities of molecules.

Straight forward synthesis of conjugated polymers for deep red to NIR PLED containing chlorine atoms on the backbone

High molecular weight and non-crosslinking conjugated donor–acceptor copolymers with chlorine on the backbones were straight forward synthesized for the first time under Stille condensation reaction by using the different reaction activities between chlorine and bromine atoms. The chlorine-bearing polymers exhibited much lower LUMO, larger Stokes shift and lower self-absorption compared with the non-chloride analogue, for the electron affinity and large steric hindrance of chlorine atoms. Deep red to NIR emission centered at 698nm was obtained with brightness about 1500cd/m2 and centered at 708nm was obtained with brightness over 400cd/m2 based on dopant/host system.

Atomic electron affinities and the role of symmetry between electron addition and subtraction in a corrected Koopmans approach

The essential aspects of zero-temperature grand-canonical ensemble density-functional theory are reviewed in the context of spin-density-functional theory and are used to highlight the assumption of symmetry between electron addition and subtraction that underlies the corrected Koopmans approach of Tozer and De Proft (TDP) for computing electron affinities. The issue of symmetry is then investigated in a systematic study of atomic electron affinities, comparing TDP affinities with those from a conventional Koopmans evaluation and electronic energy differences. Although it cannot compete with affinities determined from energy differences, the TDP expression yields results that are a significant improvement over those from the conventional Koopmans expression. Key insight into the results from both expressions is provided by an analysis of plots of the electronic energy as a function of the number of electrons, which highlight the extent of symmetry between addition and subtraction. The accuracy of the TDP affinities is closely related to the nature of the orbitals involved in the electron addition and subtraction, being particularly poor in cases where there is a change in principal quantum number, but relatively accurate within a single manifold of orbitals. The analysis is then extended to a consideration of the ground state Mulliken electronegativity and chemical hardness. The findings further emphasize the key role of symmetry in determining the quality of the results.

Monte Carlo configuration interaction applied to multipole moments, ionization energies, and electron affinities

AbstractThe method of Monte Carlo configuration interaction (MCCI) (Greer, J. Chem. Phys. 1995a, 103, 1821; Tong, Nolan, Cheng, and Greer, Comp. Phys. Comm. 2000, 142, 132) is applied to the calculation of multipole moments. We look at the ground and excited state dipole moments in carbon monoxide. We then consider the dipole of NO, the quadrupole of N2 and of BH. An octupole of methane is also calculated. We consider experimental geometries and also stretched bonds. We show that these nonvariational quantities may be found to relatively good accuracy when compared with full configuration interaction results, yet using only a small fraction of the full configuration interaction space. MCCI results in the aug‐cc‐pVDZ basis are seen to generally have reasonably good agreement with experiment. We also investigate the performance of MCCI when applied to ionisation energies and electron affinities of atoms in an aug‐cc‐pVQZ basis. We compare the MCCI results with full configuration interaction quantum Monte Carlo (Booth and Alavi, J. Chem. Phys. 2010, 132, 174104; Cleland, Booth, and Alavi, J. Chem. Phys. 2011, 134, 024112) and “exact” nonrelativistic results (Booth and Alavi, J. Chem. Phys. 2010, 132, 174104; Cleland, Booth, and Alavi, J. Chem. Phys. 2011, 134, 024112). We show that MCCI could be a useful alternative for the calculation of atomic ionisation energies however electron affinities appear much more challenging for MCCI. Due to the small magnitude of the electron affinities their percentage errors can be high, but with regards to absolute errors MCCI performs similarly for ionisation energies and electron affinities. © 2013 Wiley Periodicals, Inc.

Examining the heavy p-block with a pseudopotential-based composite method: Atomic and molecular applications of rp-ccCA

The relativistic pseudopotential variant of the correlation consistent composite approach (rp-ccCA) has been extended to lower p-block-containing molecules. The lower p-block is defined here as elements indium through iodine (In-I) and thallium through astatine (Tl-At). The accuracy of rp-ccCA has previously been established in a study of energetic properties of molecules containing 4p elements and thermodynamic data of 4d-containing molecules. In the current study, the atomic ionization potentials (IPs) and electron affinities (EAs) of In-I and Tl-At, as well as dissociation energies and enthalpies of formation of lower p-block mono-hydrides, mono-oxides, and dimers were determined with rp-ccCA. The compiled data set is referred to as the LP80 data set. The mean absolute deviation of the IPs and the EAs from the experimental data were 2.50 and 3.06 kcal mol(-1), respectively. Additionally, the total atomization energy for lead clusters (Pb(n), n = 2-6) was determined. For the lead clusters, a decrease in the total atomization energy was observed with the inclusion of spin-orbit coupling. The spin-orbit coupling of the molecules was determined with multireference configuration interaction, while scalar relativistic effects were accounted for within the pseudopotentials. The results obtained by rp-ccCA for the lower p-block support the utilization of the method in future studies where accurate energetic, spectroscopic, and thermodynamic data are necessary.

Calculations of ionization energies and electron affinities for atoms and molecules: A comparative study with different methods

In the present work, we examined the performance of 36 density functionals, including the newly developed doubly hybrid density functional XYG3 (Y. Zhang, X. Xu, and W. A. Goddard III, Proc. Natl. Acad. Sci, USA, 2009, 106, 4963), to calculate ionization energies (IEs) and electron affinities (EAs). We used the well-established G2-1 set as reference, which contains 14 atoms and 24 molecules for IE, along with 7 atoms and 18 molecules for EA. XYG3 leads to mean absolute deviations (MADs) of 0.057 and 0.080 eV for IEs and EAs, respectively, using the basis set of 6-311 + G (3df,2p). In comparison with some other functionals, MADs for IEs are 0.109 (B2PLYP), 0.119 (M06-2X), 0.159 (X3LYP), 0.161 (PBE), 0.162 (B3LYP), 0.165 (PBE0), 0.173 (TPSS), 0.200 (BLYP), and 0.215 eV (LC-BLYP). MADs for EAs are 0.090 (X3LYP), 0.090 (B2PLYP), 0.102 (PBE), 0.103 (M06-2X), 0.104 (TPSS), 0.105 (BLYP), 0.106 (B3LYP), 0.126 (LC-BLYP), and 0.128 eV (PBE0).

A systematic study of neutral and charged 3d-metal trioxides and tetraoxides

Using density functional theory with generalized gradient approximation, we have performed a systematic study of the structure and properties of neutral and charged trioxides (MO(3)) and tetraoxides (MO(4)) of the 3d-metal atoms. The results of our calculations revealed a number of interesting features when moving along the 3d-metal series. (1) Geometrical configurations of the lowest total energy states of neutral and charged trioxides and tetraoxides are composed of oxo and∕or peroxo groups, except for CuO(3)(-) and ZnO(3)(-) which possess a superoxo group, CuO(4)(+) and ZnO(4)(+) which possess two superoxo groups, and CuO(3)(+), ZnO(3)(+), and ZnO(4)(-) which possess an ozonide group. While peroxo groups are found in the early and late transition metals, all oxygen atoms bind chemically to the metal atom in the middle of the series. (2) Attachment or detachment of an electron to∕from an oxide often leads to a change in the geometry. In some cases, two dissociatively attached oxygen atoms combine and form a peroxo group or a peroxo group transforms into a superoxo group and vice versa. (3) The adiabatic electron affinity of as many as two trioxides (VO(3) and CoO(3)) and four tetraoxides (TiO(4), CrO(4), MnO(4), and FeO(4)) are larger than the electron affinity of halogen atoms. All these oxides are hence superhalogens although only VO(3) and MnO(4) satisfy the general superhalogen formula.

Quantum-chemical calculation of the electron affinity of atoms and radicals

The electron affinities of atoms and radicals were determined from energy characteristics (enthalpy and dissociation energy of o-substituted phenol) calculated by quantum-chemical methods with the use of the HyperChem 8.0.8 (Hypercube, Inc.) and GAMESS-US (version September 7, 2006) program packages. The largest correlation coefficient of 0.974 of the electron affinity-dissociation energy relationship for o-substituted phenol was obtained by the semiempirical PM3 method.

Self-Consistent Calculations on the Atomic Electron Affinity and Ionization Energy with Taking Effects of the Nonspherical Distribution of Electrons into Account

We perform the self-consistent calculations on the atomic electron affinity and ionization energy for the first-row atoms by means of our scheme. A striking feature of the present work is the variational method with taking into account effects of the nonspherical distribution of electrons explicitly. Comparing the present results with those of the conventional spherical approximation, the systematical improvement can be found. This means that effects of the nonspherical distribution of electrons may play an essential role on the description of the atomic structures.

Accuracy of Electron Affinities of Atoms in Approximate Density Functional Theory

Most approximate density functionals do not bind small atomic anions because of large self-interaction errors. Yet atomic electron affinities are often calculated using finite basis sets with surprisingly good results, despite positive highest occupied molecular orbital (HOMO) energies. We show that excellent results (better than for ionization potentials) can be obtained using standard approximate functionals evaluated on Hartree−Fock or exact-exchange densities for which the extra electron is bound. Although these good results found with limited basis sets are not accidental, we argue that this method cannot be used in general. Thus a positive HOMO indicates that the total energy should not be disregarded, only treated with caution.

Gaussian basis sets for use in correlated molecular calculations. VII. Valence, core-valence, and scalar relativistic basis sets for Li, Be, Na, and Mg

Correlation consistent basis sets of double-ζ through quintuple-ζ quality for the alkali and alkaline earth metals Li, Be, Na, and Mg have been developed, including the valence (cc-pVnZ), augmented valence (aug-cc-pVnZ), core-valence (cc-pCVnZ), and weighted core-valence (cc-pwCVnZ) basis sets. The basis sets are also re-contracted for Douglas–Kroll scalar relativistic calculations and are found to be superior to non-relativistic basis sets in recovering scalar relativistic effects. CCSD(T) computations have been performed with these basis sets, and a series of properties have been examined, including atomic ionization potentials and electron affinities, optimized molecular geometries, harmonic vibrational frequencies, atomization energies, and enthalpies of formation for the molecules Li2, LiF, BeO, BeF, BeH2, BeF2, Na2, NaF, MgO, MgF, MgH2, and MgF2.

Electron Affinity, Electronegativity, and Electrophilicity of Atoms and Ions

The electron affinity, electronegativity, and electrophilicity of several neutral atoms and their positive and negative ions are calculated at various levels of theory using different basis sets in the gas phase as well as in the presence of solvent and counterions. The electron affinity and electronegativity of all of the anions and dianions are negative in gas phase, and accordingly the electrophilicity is unexpectedly large vis-a-vis its quadratic definition. Many of these trends get altered in case the effects of solvent and counterions are taken into account.

10.1007/s11453-008-2016-7

The effect of low concentrations of two groups of doping impurities (one group includes Sn, Pb, Dy, Ho, Y and the other group includes In, Cs, and Al) on photoelectric properties of As2Se3 and (As2S3)0.3(As2Se3)0.7 was investigated. Studies of spectral distributions of photoconductivity and optical absorption showed that there is a distinct increase in photoconductivity if the level of doping with elements of the first group is as high as 0.015%. Elements of the second group of impurities did not exert any significant effect on photoconductivity. The effect of impurities of the first group is attributed to occupation of vacant sites (formed as a result of removal of highly volatile Se and S atoms) by low concentrations of impurity atoms. The observed effect is related to the fact that substitutional atoms can preserve covalent bonds and to the small difference between atomic sizes and electron affinity for doping impurities and S and Se. Atoms of the second group of impurities lack these features.

Electronic structural details of donor–vacancy complexes in Si-doped Ge and Ge-doped Si

We present a detailed picture of the electronic structure of donor–vacancy complexes in Ge-doped silicon and Si-doped germanium clusters to mimic Si-rich and Ge-rich SiGe alloys, respectively. Jahn-Teller effects and electrical levels were investigated in both Si-rich and Ge-rich end compositions. It is shown that while Ge atoms act as efficient traps for mobile E-centers in Si-rich alloys, Si atoms in Ge-rich material do not have this ability. A detailed linear combination of atomic orbitals model is proposed for VP–Ge and VP–Si complexes in Si 1 − x Ge x and Ge 1− x Si x , where the orbital filling order is driven by the larger electron affinity of Si atoms when compared to Ge.

Calculations of atomic electron affinities

The present status of calculations of atomic electron affinities is briefly reviewed. Metastable states of H(-), H(=), and He(-) are discussed. New metastable species are predicted: from Hartree-Fock (HF) data and empirical corrections it is concluded that the /sup 1/D state of P(-) lies 1.37(10)eV below the /sup 2/D/sup 0/ state of neutral P, and the /sup 1/S state of P(-) is 1.22(10)eV below the /sup 2/P/sup 0/ state of neutral P, detailed configuration-interaction calculations show that the /sup 5/S/sup 0/ state of B(-) is 0.89(2)eV below the /sup 4/P state of neutral B, and the /sup 5/S/sup 0/ state of Al(-) is similarly bound by 0.82eV at the HF level of approximation. 50 references.

Some aspects of selection of impurities improving photoelectric characteristics of chalcogenide vitreous semiconductors

The effect of low concentrations of two groups of doping impurities (one group includes Sn, Pb, Dy, Ho, Y and the other group includes In, Cs, and Al) on photoelectric properties of As2Se3 and (As2S3)0.3(As2Se3)0.7 was investigated. Studies of spectral distributions of photoconductivity and optical absorption showed that there is a distinct increase in photoconductivity if the level of doping with elements of the first group is as high as 0.015%. Elements of the second group of impurities did not exert any significant effect on photoconductivity. The effect of impurities of the first group is attributed to occupation of vacant sites (formed as a result of removal of highly volatile Se and S atoms) by low concentrations of impurity atoms. The observed effect is related to the fact that substitutional atoms can preserve covalent bonds and to the small difference between atomic sizes and electron affinity for doping impurities and S and Se. Atoms of the second group of impurities lack these features.

Local-density approximation for orbital densities applied to the self-interaction correction

A simple approximation to the functional derivative of Perdew-Zunger-type self-interaction-corrected local-spin density functional is suggested. In this approach, the orbital density |phi(isigma)(r)|(2) is regarded as a functional of the local electron density |phi(isigma)(r)|(2)=n(isigma)(n(sigma)(r)) so as to enable a functional derivative of n(isigma)(n(sigma)(r)) with respect to n(sigma)(r). Our computational results show that this approximation gives fairly good estimates of the total energy, the ionization potential, and the electron affinity for atoms. Comparative studies of this method with the averaged-density approximation and the global averaging method for the self-interaction correction are made.