Odd Number Of Valence Electrons Research Articles

Model systems for dye-sensitized solar cells: cyanidin-silver nanocluster hybrids at TiO2 support.

Theoretical study of structural, optical, and photovoltaic properties of novel bio-nano hybrids (dye-nanocluster), as well as at TiO2 surface model support is presented in the context of the application for dye-sensitized solar cells (DSSC). A group of anthocyanidin dyes (pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin) represented by cyanidin covalently bound to silver nanoclusters (NCs) with even or odd number of valence electrons have been investigated using DFT and TDDFT approach. The key role of nanoclusters as acceptors in hybrids cyanidin-NC has been shown. The nanoclusters with an even number of valence electrons are suitable as acceptors in hybrids. The interaction of bio-nano (cyanidin-NC) hybrid with the TiO2 surface model has been investigated in the context of absorption in near-infrared (NIR) and charge separation due to donor and acceptor subunits. Altogether, the theoretical concept serves to identify the key steps in the design of novel solar cells based on bio-nano hybrids at TiO2 surface for DSSC application.

Reaction Kinetics of Nitric Oxide on Size-Selected Silver Cluster Cations

We report reactions of gas-phase free silver cluster cations, Agn+ (n = 3–18), with nitric oxide molecules, which was studied by kinetics measurements using an ion trap. AgnO(NO2)m−1+ and Agn(NO2)m+ were observed as major products after multiple reactions. The reaction pathway to form these product ions was identified by fitting the data to rate equations for n ≤ 15, except for inert n = 3 and 5. Two different reaction mechanisms were found for the formation of these products depending on cluster size; pseudo-first-order rate constants of each step of elementary reactions were obtained. First, as found for n = 4, 6, and 9, AgnO+ is formed by a reaction with two NO molecules, which is followed by a release of neutral N2O. A further reaction of AgnO+ with another NO molecule produces AgnNO2+. Agn(NO2)m+ (m ≥ 1) is thus successively formed via an intermediate, AgnO(NO2)m−1+. This is analogous to the reaction of NO on silver surfaces to produce NO2. Second, both AgnNO2+ and AgnO+ are formed concurrently, as found for n = 7, 8, 10, 11, 12, and 15; AgnO+ does not act as an intermediate for AgnNO2+. AgnO(NO2)m−1+ and Agn(NO2)m+ (m ≥ 2) are formed by successive addition of NO2 to AgnO+ and AgnNO2+, respectively. It is speculated that the successive addition of NO2 proceeds via disproportionation, i.e., three NO molecules are converted to NO2 and N2O. The reaction pathways of n = 13 and 14 are explained equally well by the two mechanisms. The overall reaction rate coefficients exhibit an odd–even alternation; the higher reactivity for even values of n is due to an odd number of valence electrons.

Realization of the orbital-selective Mott state at the molecular level in Ba3LaRu2O9

Molecular magnets based on heavy transition metals have recently attracted significant interest in the quest for novel magnetic properties. For systems with an odd number of valence electrons per molecule, high or low molecular spin states are typically expected in the double exchange or quasi-molecular orbital limits respectively. In this work, we use bulk characterization, muon spin relaxation, neutron diffraction, and inelastic neutron scattering to identify a rare intermediate spin-3/2 per dimer state in the 6H-perovskite Ba$_3$LaRu$_2$O$_9$ that cannot be understood in a double exchange or quasi-molecular orbital picture and instead arises from orbital-selective Mott insulating behavior at the molecular level. Our measurements are also indicative of collinear stripe magnetic order below $T_N$ = 26(1) K for these molecular spin-3/2 degrees-of-freedom, which is consistent with expectations for an ideal triangular lattice with significant next nearest neighbor in-plane exchange. Finally, we present neutron diffraction and Raman scattering data under applied pressure that reveal low-lying structural and spin state transitions at modest pressures P $\le$ 1 GPa, which highlights the delicate balance between competing energy scales in this system.

FERMION-BOSON CLASSIFICATION IN MICROCLUSTERS

Mlcroclusters composed of atoms with non delocallzed odd number of valence electrons possess the usual magic numbers for fermions in a central potential and those with an even number of valence electrons possess the magic numbers for bosons coming from the packing of atoms in nested icosahedral or octahedral or tetrahedral shells. On the other hand, mlcroclusters composed of atoms with delocallzed valence electrons, either with an odd or with an even number of electrons, exhibit electronic magic numbers (according to the jelllum model) but also magic numbers coming from the (same, as above) packings of their bosonlc ion cores. Finally, through the present work, an alternative approach to study atomic nuclei as quantum clusters appears possible and promising.

Tuning the Electronic Properties of Hexagonal Two-Dimensional GaN Monolayers via Doping for Enhanced Optoelectronic Applications

We explore structural, electronic, and magnetic properties of two-dimensional (2D) gallium nitride (GaN) monolayer (ML) doped with different elements belonging to the groups III–VI, using density functional theory (DFT) with the Perdew–Burke–Ernzerhof (PBE) functional and the screened hybrid functional (HSE06) approaches as well as molecular dynamics (MD) simulations. Dopant interactions in Ga- and N-rich environments are investigated by varying their concentrations from 1.38 to 5.5%. Our calculations reveal that oxygen and aluminum impurities are the most preferred candidates under Ga- and N-rich conditions, respectively. The electronic structure studies indicate that dopants containing an even number of valence electrons introduce magnetic behavior with spin-polarized properties, or n-type conductivity with nonmagnetic features, depending on the stoichiometric III/V ratio during growth. Dopants with an odd number of valence electrons modify the GaN ML band structure from indirect to direct bandgap at the Γ point, depending on dopant types at different III/V ratios as well as substitutional site. The calculated charge transfer explains the dopants’ influence on the band structure and bond nature. The HSE calculations of doped g-GaN MLs show a 0.23–1.48 eV increase in the band gaps including the spin-polarized band structures when compared with their PBE values. MD calculations suggest high structural stability at high growth temperatures. Such dopant-induced modifications in structural and physical properties of 2D GaN ML could potentially allow use of this material in diverse electronic, optoelectronic, and spintronic applications.

Magnetism in monolayer InSe by nonmetal doping: First-principles study

To develop InSe-based spintronics devices, introducing magnetism into monolayer InSe is essential. In this work, the electronic and magnetic properties of nonmetal (NM) doped (H, B, C, Si, N, P, As, O, S, Te, F, Cl, Br and I) monolayer InSe were investigated by first-principles calculations. The results indicate that atoms from VA, VIA and VIIA groups are possible to substitute Se atoms under In-rich condition. Second, we have found that only the InSe doped with NM acceptors with odd number of valence electrons possesses magnetism. Especially B doped InSe is a half-metal. However, VIIA group doped InSe does not exhibit magnetism due to the In-In covalent bond. This work provides an important guidance for developing spintronic devices on monolayer InSe.

Tuning the magnetic properties of the monolayer MoSe2 by nonmetal doping: First-principles study

The magnetic properties of nonmetal (NM) doped (H, B, C, Si, N, P, As, O, S, Te, F, Cl, Br or I) monolayer MoSe2 were investigated by first principle calculations. We have found that NM dopants with odd number of valence electrons can induce magnetism; on the contrary, NM dopants with even number of valence electrons cannot induce magnetism. More importantly, half metallic property has been found for H-, B-, F-, Cl-, Br- and I-doped MoSe2, characterized with 100% spin-polarization around the Fermi level. This work has important guidance for the realization of spin devices on monolayer MoSe2.

First-principles study of nonmetal doped monolayer MoSe2 for tunable electronic and photocatalytic properties

Recently, two dimensional transition metal dichalcogenides become popular research topics because of their unique crystal and electronic structure. In this work, the geometrical structure, electronic, electrical transport, redox potentials and photocatalytic properties of nonmetal (H, B, C, Si, N, P, As, O, S, Te, F, Cl, Br and I) doped monolayer MoSe2 were investigated by first principle calculations. The binding energy indicates that nonmetal doped MoSe2 are energetically favorable compared to Se vacancies, except B- and C-doped. We have found that nonmetal dopants with an even number of valence electrons doped MoSe2 have p-type conductivity. On the contrary, nonmetal dopants with an odd number of valence electrons doped MoSe2 have p-type or n-type conductivity; and they have better photocatalytic performance.

Geometrical structure, stability and electronic properties of AunHg( $1 \leq n \leq 12$ ) clusters

The geometrical structures, relative stabilities, electronic properties and chemical hardness of AunHg( $ n=1-12$ ) clusters are systematically investigated using the density functional theory with relativistic all-electron methods. The optimized low-lying energy geometries exhibit two-dimensional and three-dimensional structures. Furthermore, all the lowest-energy structures of AunHg( $ n=1-12$ ) clusters favor planar geometries with slight distortion, in which the dopant Hg atom prefers to occupy a peripheral site with a lower coordination. The geometrical, electronic and chemical stabilities of the AunHg cluster with even number of valence electrons are higher than those of the neighboring AunHg cluster with odd number of valence electrons. Besides, 5d valence electrons of impurity Hg atom in the AunHg cluster hardly join in the orbital interactions compared with 5d valence electrons of corresponding Au atom in Aun+1 cluster. Au-Hg bonds in AunHg clusters are weaker and have more obviously ionic-like characteristics than the corresponding Au-Au bonds in Aun+1 clusters.

Anomalous doping effect in black phosphorene using first-principles calculations.

Using first-principles density functional theory calculations, we investigate the geometries, electronic structures, and thermodynamic stabilities of substitutionally doped phosphorene sheets with group III, IV, V, and VI elements. We find that the electronic properties of phosphorene are drastically modified by the number of valence electrons in dopant atoms. The dopants with an even number of valence electrons enable the doped phosphorenes to have a metallic feature, while the dopants with an odd number of valence electrons retain a semiconducting feature. This even-odd oscillating behavior is attributed to the peculiar bonding characteristics of phosphorene and the strong hybridization of sp orbitals between dopants and phosphorene. Furthermore, the calculated formation energies of various substitutional dopants in phosphorene show that such doped systems can be thermodynamically stable. These results propose an intriguing route to tune the transport properties of electronic and photoelectronic devices based on phosphorene.

Theoretical investigation on structural evolution, energetic stability trend and electronic properties of Au n Cd(n=1–12)

We systematically studied the geometrical structures, relative stabilities, electronic properties and chemical hardness of Au n Cd (n =1–12) clusters based on the framework of the density functional theory using relativistic all-electron methods. Low-lying energy structures include two-dimensional and three-dimensional geometries. Especially, all the lowest-energy structures of Au n Cd (n =1 −12) clusters are inclined to be planar geometries with slight distortion, in which the dopant Cd atom has higher coordination at n =2–6, but lower coordination at n =7–12. The fragmentation energies, second-order difference of energies, the highest occupied–lowest unoccupied molecular orbital gaps and chemical hardness of Au n Cd and Au n+1 exhibit a pronounced even–odd alternations phenomenon in the reverse order This result indicates that the geometrical, electronic and chemical stabilities of Au n Cd with even number of valence electrons are higher than those of the neighbouring Au n Cd with odd number of valence electrons and corresponding Au n+1 with odd number of valence electrons. Additionally, 4d valence electrons orbital of impurity Cd atom in Au n Cd hardly joins in the orbital interactions compared with 5d valence electrons of corresponding Au atom in Au n+1. Au–Cd bonds of Au n Cd clusters are weaker and have more obviously ionic-like characteristics than the corresponding Au–Au bonds of Au n+1. The impurity Cd atom can change the chemical stability pattern of pure gold clusters, namely the even-numbered Au n Cd are less reactive than the corresponding Au n+1 and neighbouring odd-numbered Au n Cd.

Reactivity of silver clusters anions with ethanethiol.

We have investigated the gas-phase reactivity of silver clusters with ethanethiol in a fast-flow tube reactor. The primary cluster products observed in this reaction are AgnSH(-) and AgnSH2(-), indicating C-S bond activation, together with interesting byproducts H3S(-) and (H3S)2(-). Agn(-) clusters with an odd number of valence electrons (n = even) were observed to be more reactive than those with an even number of electrons-a feature previously only observed in the reactivity of Agn(-) with triplet oxygen, indicating that radical active sites play a role in their reactivity. Furthermore, the reactivity dramatically increases with large flow rate of ethanethiol being introduced in the flow tube. Theoretical investigations on the reactivity of Ag13(-) and Ag8(-) with ethanethiol indicate that both Ag13(-) and Ag8(-) face significant barriers to reactivity with a single ethanethiol molecule. However, Ag8(-) reacts readily in a cooperative reaction with two ethanethiol molecules, consistent with the dramatic increase in reactivity with a large flow rate. Further hydrogen-transfer reactions may then release an ethylene molecule or an ethyl radical resulting in the observed AgnSH(-) species.

Density functional study of structural and electronic properties of AlnAs (1 ≤ n ≤ 15) clusters

Energetically low-lying equilibrium geometric structures of AlnAs (n=1–15) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied with the three-parameter hybrid generalized gradient approximation (GGA) due to Becke–Lee–Yang–Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static dipole polarizabilities are calculated for the ground-state structures within the same method. The growth pattern for AlnAs (n=1–15) clusters is As-substituted the surface atom of Aln+1 clusters and it keeps the similar frameworks of the most stable Aln+1 clusters except for AlnAs (n=7, 8, and 15) clusters. The odd–even oscillations in the dissociation energy, the second differences in energy, the HOMO–LUMO gaps, the electron affinity, and the hardness are more pronounced. The stability analysis based on the energies clearly shows the clusters with an even number of valence electrons are more stable than clusters with odd number of valence electrons.

The structure and energetic of AlAs n ( n = 1–15) clusters: A first-principles study

Geometric structures of AlAs n ( n = 1–15) clusters are reported. The binding energy, dissociation energy, stability of these clusters are studied with the three-parameter hybrid generalized gradient approximation (GGA) due to Becke–Lee–Yang–Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated for the ground-state structures within the same method. The growth pattern for AlAs n ( n = 6–15) clusters is Al-substituted pure As n+1 clusters and it keeps the similar frameworks of the most stable As n+1 clusters (for example AlAs 6, AlAs 7, AlAs 9, AlAs 14 and AlAs 15 clusters) or capping the different sides of the low-lying geometry of As n clusters (for example AlAs 8, AlAs 10, AlAs 11, and AlAs 12 clusters). The Al atom prefer to occupy a peripheral position for n < 12, and starting from n = 12 clusters, the Al atom completely falls into the center of the As frame. The above growth pattern is not suitable for AlAs n ( n = 1–5, 13) clusters. The odd–even oscillations from AlAs n ( n = 5–15) in the dissociation energy, the second-order energy differences, the HOMO–LUMO gaps, the electron affinity, and the hardness are more pronounced. The stability analysis based on the energies clearly shows the AlAs n clusters from n = 5 with an even number of valence electrons are more stable than clusters with odd number of valence electrons.

Computational investigation of GanAl (n=1–15) clusters by the density-functional theory

Low-lying equilibrium geometric structures of aluminum-doped gallium cluster GanAl (n = 1–15) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied with the three-parameter hybrid generalized gradient approximation (GGA) due to Becke-Lee–Yang–Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated for the ground-state structures within the same method. The growth pattern for GanAl (n = 1–15) clusters is Al-substituted Gan + 1 clusters and it keeps the similar frameworks of the most stable Gan + 1 clusters except for Ga8Al and Ga13 Al clusters. The Al atom substituted the surface atom of the Gan + 1 clusters for n < 12. Starting from n = 12, the Al atom completely falls into the center of the Ga-frame. The Al atom substituted the center atom of the Gan + 1 clusters to form the Al-encapsulated Gan geometries for n > 12. The odd−even oscillations from GanAl (n = 5) in the dissociation energy, the second-order energy differences, the HOMO–LUMO gaps, the ionization potential, the electron affinity, and the hardness are more pronounced. The stability analysis based on the energies clearly shows the clusters from n = 5 with an even number of valence electrons are more stable than clusters with odd number of valence electrons.

How cationic gold clusters respond to a single sulfur atom

Results describing the interaction of a single sulfur atom with cationic gold clusters (Au(n) (+), n=1-8) using density functional theory are described. Stability of these clusters is studied through their binding energies, second order differences in the total energies, fragmentation behavior, and atom attachment energies. The lowest energy structures for these clusters appear to be three dimensional right from n=3. In most cases the sulfur atom in the structure of Au(n)S(+) is observed to displace the gold atom siting at the peripheral site of the Au(n) (+) cluster. The dissociation channels of Au(n)S(+) clusters follow the same trend as Au(n) (+) cluster, based on the even/odd number of gold atoms in the cluster, with the exception of Au(3)S(+). This cluster dissociates into Au and Au(2)S(+), signifying the relative stability of Au(2)S(+) cluster regardless of having an odd number of valence electrons. Clusters with an even number of gold atoms dissociate into Au and Au(n-1)(S)(+) and clusters with an odd number of gold atoms dissociate into Au(2) and Au(n-2)(S)(+) clusters. An empirical relation is found between the conduction molecular orbital and the number of atoms in the Au(n)S(+) cluster.

Density functional study of structural and electronic properties of Al n P (2 ≤ n ≤ 12) clusters

Low-lying equilibrium geometric structures of Phosphorus-doped aluminum cluster AlnP (n = 2–12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spin-polarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static polarizabilities are calculated for the ground-state structures within the GGA. It is observed that symmetric structures with the P atom occupying a peripheral position are lowest-energy geometries of AlnP (n = 2, 4–11), while the P impurities of Al3P and Al12P prefer to occupy internal sites in the aluminum clusters. Generalized gradient approximation extends bond lengths as compared to the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the HOMO–LUMO gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within both GGA and LSDA. The stability analysis based on the energies clearly shows the clusters with an even number of valence electrons are more stable than clusters with odd number of valence electrons.

Different Ways of P4 Transformation in the Coordination Sphere of Transition Metals

Abstract The transformation pathway of tetrahedral P4 to the corresponding Pn ligands has been studied by the three-component-reaction are found to depend on the electron number of the complex fragments used. In the case of complexes forming fragments with an even number of valence electrons, a stepwise P-P bond cleavage is observed with a bicyclotetraphosphine intermediate to give a cyclo-P4 containing product. Complexes with an odd number of valence electrons cause a P1/P3 fragmentation. A possible product of this reaction is a phosphido complex of the type [LnM≡P→M′(CO)5] (M′ = Cr, W), which is self-stabilised by dimerisation. The phosphido complex [(tBuO)3W≡P→M(CO)5] (M = Cr, W) is formed via the reaction of W2(OtBu)6 with RC≡P in the presence of the Lewis acids [M(CO)5THF].