Adiabatic Electron Affinity Research Articles

Theoretical Study on Structural Stability, Growth Behavior and Photoelectron Spectroscopy of Copper-Doped Germanium Clusters CuGen−/0 (n = 4–13)

Studies on Cu-doped germanium clusters in the neutral and mono-anion states CuGen−/0 (n = 4–13) are carried out employing a double-hybrid density functional mPW2PLYP scheme. The global minimal structure, spectral property, HOMO–LUMO gap, and stability of CuGen−/0 (n = 4–13) were confirmed. The results showed that the global minimal structures of the anionic clusters are Cu-substituted for a Ge in the ground state of anionic Gen+1− with n ≤ 8, and Cu atom is encapsulated into germanium cages starting from n = 9. For neutral, it is also Cu-encapsulated into cage-like Ge framework with n ≥ 9. The spectra information including adiabatic electron affinity, vertical detachment energy and simulated photoelectron spectroscopy were presented. The HOMO–LUMO gap, atomization energy, and second energy difference for CuGen−/0 (n = 4–13) clusters along with NICS of CuGe12− were evaluated to examine the thermodynamic and chemical stability. The results revealed that anionic cluster CuGe12− with a high-symmetry endohedral Ih configuration possessed a perfect thermodynamic stability and chemical reactivity, making it possible as appropriate building block for new multi-functional semiconductor materials.

Study on the growth patterns and simulated photoelectron spectroscopy of double vanadium atoms doped silicon clusters V2Sin(n ≤ 12) and their anions

Double vanadium atoms doped silicon clusters V2Sin (n ≤ 12) and their anionic species were investigated using the Perdew–Burke–Enzerhof (PBE) method combined with the ABCluster algorithm. The growth patterns of the most stable structures of neutral V2Sin and their anions are seen to derive from V2Sin-1 by absorbing a silicon atom. Their simulated photoelectron spectroscopy (PES), vertical detachment energy (VDE), adiabatic electron affinity (AEA), relative stability, and charge transfer were also calculated. With the exception of V2Si3, the average absolute errors of VDE and AEA are 0.12 and 0.165 eV compared with the available experimental values. Both neutral and anionic V2Si10 clusters possessed high stability and low chemical reactivity. Compared with neutral molecules, the 3d orbital of negatively charged ions had fewer electrons due to the arrangement of extra-nuclear electrons in anionic clusters belonging to the open-shell.

Quantum chemistry calculations of the growth patterns, simulated photoelectron spectra, and electronic properties of LaASil (A = Sc, Y, La; l ≤ 10) compounds and their anions.

The growth patterns, simulated photoelectron spectra, and electronic properties of LaASil (A = Sc, Y, and La; l ≤ 10) compounds and their anions were studied via quantum chemistry calculations using the Perdew-Burke-Ernzerhof (PBE) method and unprejudiced structural searching software ABCluster. The results revealed that the growth patterns of the most stable structures of neutral and anionic LaASil showed an adsorptive mode. The lowest-energy structures (LESs) of the LaASil (l ≤ 7) clusters were similar, except for those of anionic LaYSi4- and LaYSi5- and neutral LaScSi7. Additionally, we investigated and calculated the photoelectron spectra, vertical detachment energies, adiabatic electron affinities, relative stability, charge transfer, magnetic moment, and chemical bond analysis of the LaASil ground-state structures. The La2Sil clusters exhibited higher stability than the LaYSil and LaScSil systems owing to their higher dissociation energies (DEs). The DEs of the LESs in the LaASi3 molecule are higher than those of other clusters. Thus, the LaASi3 cluster shows potential as a building framework for Si-based cluster materials with good stability. The natural population analysis data and chemical bond analysis results showed that the spd hybridization of the orbitals of the metal atoms in the LaASil system occurred. Except for the LaScSi9 and LaScSi10 clusters, the neutral LaASil compounds transform into the corresponding anions when an extra electron is accepted by the Si clusters.

Geometric and electronic properties of AulPtm (l + m ≤ 10) clusters: a first-principles study.

The structural evolutions and electronic properties of AulPtm (l + m ≤ 10) clusters are investigated by using the first-principles methods. We use the inverse design of materials using the multi-objective differential evolution (IM2ODE) package to globally search the equilibrium structures and investigate the evolving trend from a two-dimensional structure to a three-dimensional structure on horizontal extension and vertical extension for AulPtm (l + m ≤ 10) clusters. The three-dimensional stable geometry of Au8Pt and Au8Pt2 is discovered for the first time in our work. We also notice that the equilibrium structures of AulPtm (l + m = 10 and l ≤ 8) tend to form a tetrahedral geometry and can be obtained by replacing the Au atom in the most stable structure of Aul+1Ptm-1 with the Pt atom, where Pt atoms assemble together and occupy the center of clusters and Au atoms prefer to lie on the vertex or edge position. The average binding energy (Eb) is mostly decided by Pt-Pt bond numbers, namely the numbers of Pt atoms, followed by Au-Pt bond numbers. The second-order energy difference (Δ2Ev and Δ2Eh) and the nearest-neighbor energy difference (Δ4Enn) show that Au6Pt, Au4Pt2, Au3Pt3, Au2Pt4 and AuPt7 clusters exhibit high relative physical stability, so we suggest that these clusters could be defined as the magic number clusters for AulPtm (l + m ≤ 10) clusters. The HOMO-LUMO energy gap (Eg), adiabatic ionization potential (AIP) and the adiabatic electron affinity (AEA) are also investigated to elaborate the relative electronic stability of all the clusters.

Theoretical study on adiabatic electron affinity of fatty acids

The AEA of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids with typical substituents were calculated by the ωB97X method.

Efficient EOM-CC-based Protocol for the Calculation of Electron Affinity of Solvated Nucleobases: Uracil as a Case Study.

We present an explicit solvation protocol for the calculation of electron affinity values of the solvated nucleobases. The protocol uses a quantum mechanics/molecular mechanics (QM/MM) approach based on the newly implemented domain-based pair natural orbital EOM-CCSD (equation-of-motion coupled-cluster single-double) method. The stability of the solvated nucleobase anion is sensitive to the local distribution of the water molecules around the nucleobase, and the calculated electron affinity values converge slowly with respect to the number of snapshots and the size of the water box. The use of nonpolarizable water molecules leads to an overestimation of the electron affinity and makes the result sensitive to the size of the QM region in the QM/MM calculation. The electron affinity values, although sensitive to the size of the basis set, lead to an almost constant blue shift of the electron affinity upon the increase in the basis set. The present protocol allows for a controllable description of the various parameters affecting the electron affinity value, and the calculated adiabatic electron affinity values are in excellent agreement with experimental results.

Quantum‐chemical investigation of the phosphine ligand effects on the structure and electronic properties of a rhenabenzyne complex

AbstractThis study examined the effects of phosphine ligand on the structure and electronic properties of (C5H4)Re(PX3)3Cl rhenabenzyne complexes (X = H, F, Cl, Me) using the hybrid density functional MPW1PW91. Variations in the structure, dipole moment, electronic spatial extent (ESE), and aromaticity of the title complex were studied. In addition, adiabatic and vertical ionization potential and electron affinity values of these complexes were calculated. Correlations between the calculated parameters and Tolman cone angles (θ), Tolman's Electronic Parameter (TEP), as well as the Crabtree's DFT Electronic Parameter (CEP) of the phosphine ligands were illustrated. The para‐delocalization index (PDI) was used to investigate aromaticity in these systems. Natural bond orbital analysis (NBO) was employed for a comprehensive insight into the nature of the bonds in these complexes.

Determination of Electron Affinity on the Base of Experimentally Measured Lifetime of Negative Molecular Ions of Coumarin Derivatives

Resonance attachment of low-energy (0–15 eV) electrons to molecules of 4.7- and 6.7-dihydroxycoumarin was investigated by means of negative ion mass spectrometry. These natural compounds possess biological activity associated with antioxidant and bactericidal properties. The most probable structures of the fragment negative ions ([M – H]–, [M – 2H]–, [M – СО]–, [M – СОH]–, [M – СООH]– etc.) were predicted by means of analysis of decay channels for the molecular negative ions using the results of density functional theory calculations. Mean lifetime for molecular negative ions of 4.7-dihydroxycoumarin relative to electron autodetachment was measured. The adiabatic electron affinity (EAa) was estimated in the framework of the Arrhenius approximation. It was found that EAa values calculated at B3LYP/6-31+G(d) level with minimal addition of diffuse functions as a difference between the total energies of a neutral molecule and its radical anion correlate with experimental EAa values.

Probing the electronic structures and properties of neutral and charged FeSin(-1,0,+1) (n = 1-6) clusters using ccCA theory.

The equilibrium structures and electronic properties such as relative stabilities, electron affinities, and charge transfer of small neutral and charged FeSin(-1,0,+1) (n = 1-6) clusters have been systematically studied using the high level of the correlation consistent Composite Approach (ccCA) method. The lowest-energy geometries of these clusters can be regarded as "substitutional structure." It is derived from Sin + 1(and/or Si-n + 1) clusters by replacing a silicon atom with an iron atom. The adiabatic electron affinities (AEAs) and the adiabatic ionization potentials (AIPs) have also been predicted by ccCA schemes for FeSin(n = 1-6) and their ions. The dissociation energies of an iron or a silicon atom from the ground-state structure of FeSin clusters have been evaluated to check relative stabilities of FeSin(-1,0,+1) (n = 1-6) clusters. Compared with other clusters, neutral and charged FeSi2 possess higher stability. As for the neutral clusters and the negatively charged ions, the theoretical charges of the iron atom in FeSin (n = 1-6) species (except for FeSi and FeSi2-) show that silicon clusters act as an electron donor. For the cationic species, however, the charge transfers from iron atom to silicon clusters (except for FeSi3+) show that the iron atom acts as electron donor.

A theoretical insight into the reducing properties of bicyclic dithia hydrocarbons and hetero-bicyclic dithiolopyrrolone compounds with rotation-restricted planar disulfide linkage

The current study primarily involves the investigation of reducing properties of dithia-substituted bicyclic hydrocarbons. Adiabatic electron affinities (AEA) of the selected dithiabicyclic systems were investigated under gas and aqueous phase conditions. Calculated AEA values suggest the neutral-anion radical of the systems to be a perfect redox couple similar to cystines. Higher affinity to capture an electron is obtained in the aqueous environment. Natural bond orbital and atoms in molecule analyses were performed to obtain insight into the S–S bonding properties. One electron added radicals with elongated disulfide linkage indicates the viability of the systems towards rupturing upon reduction making it more suitable in drug carrier designing. The current investigation is also extended to biologically important dithiolopyrrolone (DTP) class of compounds and compared with dithiabicyclic hydrocarbons. The AEA range for neutral DTPs is found to be higher indicating more tendency of these systems to get reduced.

Size dependence in the electronic and optical properties of a BN analogue of two-dimensional graphdiyne: A theoretical study

In this study, we propose a new type of a BN analogue of two-dimensional (2D) graphdiyne. By DFTB, we carried out the changes in the electronic and optical properties of BNdiyne based on size. Higher binding energies with increase size ensure an increase in the stability of BNdiyne. Considerable decrease in the energy gap from 1.09 eV to 0.02 eV suggests BNdiyne transforms from a semiconductor to metal, thus an increase in electrical conductivity. The HOMO energy of BNdiyne with size contributes the stability. The increase in the size induces a decrease in adiabatic electron affinity and chemical hardness, but an increase in the refractive index, adiabatic ionization potential, electrophilicity index and maximum amount electronic charge index which enhance the energy stability of the BNdiyne during charge transfer. These findings herein indicate that new 2D-BNdiyne can be used in promising applications from nanosensors to solar cell applications.

Electronic and photocatalytic properties of Antimonene nanosheets

Electronic and photocatalytic properties of single-layer Antimonene nanosheets have been investigated. The variation of the energy gap between HOMO and LUMO levels concerning the nanosheet width along with both armchair and zigzag directions has been explored up to 388 atoms. It is shown that the armchair edges in Antimonene nanosheet are chemically more active than that of zigzag edge. Here, we also report that the Antimonene nanosheet can demonstrate photocatalytic properties for the whole range of pH. Besides, the density of energy states for these two frontier orbitals around the energy gap is reported. Interestingly, while the adiabatic electron affinity demonstrates a similar pattern for the two mentioned edges, the adiabatic ionization energy is mainly controlled by the length of the armchair edge. • Size-dependency of the Antimonene nanosheets for electronic and photocatalytic properties are presented. • Antimonene nanosheet can demonstrate photocatalytic properties for the whole range of pH. • The adiabatic ionization energy is mainly controlled by the length of the armchair edge. • The adiabatic electron affinity demonstrates a similar pattern for the two mentioned edges.

All-electron basis sets augmented with diffuse functions for He, Ca, Sr, Ba, and lanthanides: application in calculations of atomic and molecular properties.

Non-relativistic and Douglas-Kroll-Hess (DKH) basis sets augmented with diffuse functions for He, Ca, Sr, Ba, and lanthanides are generated. These sets are appropriated to describe electrons away from the nuclei. Using the DKH augmented sets along with the B3LYP functional, bond lengths, dissociation energies, harmonic vibrational frequencies, adiabatic ionization potentials, adiabaticelectron affinities, anddipole moments for CaH, SrH, and BaH are computed. These results agree well with the most recent experimental and benchmark theoretical data published in the literature. The DKH mean dipole polarizabilities reported in this work for some elements are close to the recommended values. Scalar relativistic effects are also estimated.

Theoretical Study of the Negative Ion Photoelectron Spectrum of Cyclooctatetraene via Computation of Franck-Condon Factors.

The equilibrium structures and harmonic vibrational frequencies of the anion and the first triplet state of cyclooctatetraene were computed using the B3LYP, PBE0, and M06-2X approaches of the density functional theory associated with the aug-cc-pVTZ basis set. The first excited singlet state of cyclooctatetraene was calculated using the complete active space self-consistent field method. The photoelectron spectra of cyclooctatetraene anion were simulated for both the triplet and the excited singlet states via computing Franck-Condon factors. The adiabatic electron affinity was computed by extrapolation to the complete basis set limit from the energies calculated using CCSD(T)/aug-cc-pVXZ (X = D, T, Q). The simulated photoelectron spectrum and the calculated adiabatic electron affinity for the triplet state are in consistence with the experiment. The first excited singlet state, which plays a key role in the photochemistry of cyclooctatetraene, is predicted to possess vibrational structures in its photoelectron spectrum pertinent for experimental identification.

Quantum-Chemical Modeling of the Efficiency of Using Polymers in Interface Structures

In this work, a quantum-chemical analysis of the effectiveness of the use of polyarylenephthalides in interface structures is carried out. Quantum chemical calculations are performed for molecular systems, which are model polymer systems of the polyarylene class — polyarylenephthalides. In total, 9 representatives of this class of compounds are considered. Quantum chemical calculations are performed for all molecules using the density functional theory method B3LYP/6-31 +G(d) and such energy parameters as the total energies of the molecules and their negative and positive ions in molecular and optimized ionic geometries; energies of occupied and vacant molecular orbitals; the values of vertical and adiabatic electron affinity and ionization potential, as well as the dipole moment are theoretically estimated. In this paper, the authors propose an algorithm for processing the results of quantum-chemical calculations based on the analysis of the energy characteristics of the polymer monomer unit, which makes it possible to reveal a certain relationship between the chemical structure of the organic compound and the electronic properties of the metal/polymer interface. The proposed algorithm makes it possible to identify areas of maximum deviation of energy parameters and specific compounds that are of interest for the formation of heterostructures. The correlation of the results obtained using the methods of quantum chemical modeling with the experimental results on the determination of potential barriers at the metal/polymer interface and conductivity along the polymer/polymer interface is shown.

Electron Binding in a Superatom with a Repulsive Coulomb Barrier: The Case of [Ag44(SC6H3F2)30]4- in the Gas Phase.

The electron binding mechanism in [Ag44(SC6H3F2)30]4- (SC6H3F2 = 3,4-difluorobenzenethiolate) tetra-anion was studied by photoelectron spectroscopy (PES), collision-induced dissociation mass spectrometry (CID-MS), and density functional theory (DFT) computations. PES showed that [Ag44(SC6H3F2)30]4- is energetically metastable with respect to electron autodetachment {[Ag44(SC6H3F2)30]3- + e-} and features a repulsive Coulomb barrier (RCB) with a height of 2.7 eV. However, CID-MS revealed that [Ag44(SC6H3F2)30]4- does not release an electron upon collisional excitation but undergoes dissociation. DFT computations performed on the known structure of [Ag44(SC6H3F2)30]4- confirmed the negative adiabatic electron affinity of [Ag44(SC6H3F2)30]3- and interpreted the experimental PE spectrum by taking into account tunneling electron photodetachment through the RCB.

Dissociative Electron Attachment to 2,3,6,7,10,11-Hexabromotriphenylene.

2,3,6,7,10,11-Hexabromotriphenylene (HBTP) and 2,3,6,7,10-pentabromotriphenylene (PBTP) were investigated by means of dissociative electron attachment spectroscopy (DEAS). The dominant decay channel of the transient molecular negative ions consists of elimination of Br- with resonances in the low electron energy region. Formation of long-lived parent anions with autodetachment lifetime τa = 310 μs is observed at thermal electron energies. The adiabatic electron affinities, EAa = 1.12 ± 0.1 eV in HBTP and 1.09 ± 0.1 eV in PBTP, evaluated using a simple Arrhenius approach are in good agreement with those predicted by DFT (XYG3/Def2-TZVPP//PBE0/Def2-TZVPP) calculations.

Structural properties of possible interstellar valence anions of the series HCnN- (n = 3, 5, 7, 9).

In this contribution we investigate the structural properties of stable anions of small carbon clusters, with one nitrogen and one hydrogen atoms attached to the C-cluster, to surmise their possible existence in the Interstellar Medium (ISM). Many possible configurational (geometrical) isomers with positive vertical electron detachment values are presented, and arranged according to their relative energy. Specific attention is paid to the structures of the lowest-energy valence isomers, the chain-structures of HC7N- and HC9N- anions with quasilinear and linear geometry, respectively. They exhibit relatively large permanent dipole moments (2.697 and 5.034 Debye) and adiabatic electron affinities (AEAs) of 1.13 and 1.35 eV. Isomers of the HNCn- family and many branched structures are possible stable species viable for detection in the ISM.

The photoelectron-imaging spectroscopic study and chemical bonding analysis of VO2 -, NbO2 - and TaO2.

The transition-metal di-oxides, namely VO2−, NbO2− and TaO2− have been studied using photoelectron velocity map imaging (PE-VMI) in combination with theoretical calculations. The adiabatic electron affinities of VO2−, NbO2− and TaO2− are confirmed to be 2.029(8), 1.901(10) and 2.415(8) eV, respectively. By combining Franck–Condon (FC) simulation with theoretical calculations, the vibrational feature related to Nb–O and Ta–O stretching modes for the ground state has been unveiled. The photoelectron angular distribution (PAD) for VO2−, NbO2− and TaO2− is correlated to the photo-detachment of the highest occupied molecular orbitals (HOMOs), which primarily gets involved in s- and d-orbitals of the V, Nb and Ta atoms. A variety of theoretical calculations have been used to analyze the chemical bonding features of VO2−1/0, NbO2−1/0 and TaO2−1/0, which show that the strong M–O (M = V, Nb and Ta) bond is mainly characterized as ionicity.

The Watson-Crick rare tautomer hypothesis of mutations and reality

Background: In their Nature's seminal work (Nature. 1953;171:737), J.D. Watson and F.H.C. Crick noted that the structure of DNA admits a so-called tautomeric model of spontaneous point mutations. This work reported at the conference "Nanobiophysics-2019" (Kiev) as a plenary report, is actually an attempt to answer the following questions: (i) "Yes, the tautomerism of the bases is a very attractive model, but how important is it in mutagenesis?" by Morgan (Morgan AR. Trends Biochem. Sci. 1993;18:160–163); (ii) What reality does the rare tautomeric mutation model describe? The structure [А×Т]WC was selected in the work. Developing the previously proposed mutation model×of the Watson-Crick pair [А×Т]WC due to the shift of the bases in the pair relative to each other and the interconnection hydrogen bonds (Kryachko ES, Sabin JR. Int. J. Quantum Chem. 2003;91:695–710), it is shown that some resultant structures possess the electron affinity that is 1.7 times higher compared to the canonical pair, which is definitely of interest in the view of the numerous phenomena associated with a charge transfer in and attachment of an electron to DNA. Objectives: Answer the questions raised in the Background, and show the realism of the tautomeric [А×Т]WC-mutation model modified in the present work on the example of the Watson-Crick pair [А×Т]WC that is dubbed as a pair-tautomerism model. Materials and Methods: The key method is a computer simulation based on the density functional method. All calculations performed in the present work use the package of programs GAUSSIAN with the density functional method invoking the Becke-Lee-Yang-Parr density functional, B3LYP. Results: The paper shows the existence and stability of paired tautomeric mutations in a pair of adenine-thymine and investigates to what wobble pairs it can lead. It is also shown that, due to the specific structure of the paired tautomeric mutation of the adenine-thymine pair, the mutation possesses a larger electronic affinity in comparison with the pair that it generates, and thus can be observed in reality and through it one can explain a number of phenomena of charge transfer in DNA, which, again, emphasizes its reality. Conclusions: On the one hand, a generalization of the Watson-Crick tautomeric hypothesis, proposed in this work, specifically for the adenine-thymine pair, the name of the paired tautomeric mutation. This mutation refers to dipole-binding-electron systems, which implies their high adiabatic electron affinity. The latter, on the other hand, emphasizes the realism of the proposed mutational model and its possible application to the explanation of the phenomena of charge transfer in DNA and the processes of attachment electron to DNA.