Theoretical Investigation of Square-Planar MXe42+ (M = Cu, Ag, Au) Cations

2009 ◽  
Vol 62 (11) ◽  
pp. 1556 ◽  
Author(s):  
PingXia Zhang ◽  
YongFang Zhao ◽  
XiuDan Song ◽  
GuoHua Zhang ◽  
Yang Wang
Keyword(s):  
Theoretical Investigation ◽  
Electrostatic Interactions ◽  
Relativistic Effect ◽  
Noble Gas ◽  
Theoretical Estimate ◽  
Binding Energies ◽  
Bonding Mechanism ◽  
Metal Bonding ◽  
Square Planar ◽  
Doubly Charged

The structures, stabilities, and bonding mechanism of the square-planar doubly charged MXe42+ (M = Cu, Ag, Au) cations have been investigated at the UB3LYP and UMP2 theoretical levels. At the best theoretical estimate, the M–Xe bond lengths are calculated to be 266.2, 273.6, and 273.8 pm, and the corresponding binding energies with respect to M2+ and four xenon atoms are 771.49, 820.57, and 908.47 kJ mol–1, respectively, along the series Cu – Ag – Au. Owing to an unusually high relativistic effect, gold evidently tends to be strongly bonded to the noble gas atoms in comparison with copper and silver. The electrostatic interactions play an important role in divalent noble-gas–noble-metal bonding. Apart from CuXe42+, the square-planar MXe42+ cations are stable enough to be prepared in experiments.

Serine–Ca2+ versus serine–Cu2+ complexes — A theoretical perspective

2010 ◽  
Vol 88 (8) ◽  
pp. 759-768 ◽  
Author(s):  
Al Mokhtar Lamsabhi ◽  
Otilia Mó ◽  
Manuel Yáñez
Keyword(s):  
Gas Phase ◽  
Electron Density ◽  
Potential Energy Surfaces ◽  
Metal Ion ◽  
Theoretical Perspective ◽  
Binding Energies ◽  
Interacting Systems ◽  
Intramolecular Hydrogen ◽  
Energy Surfaces ◽  
Doubly Charged

The association of Ca2+ and Cu2+ to serine was investigated by means of B3LYP DFT calculations. The [serine–M]2+ (M = Ca, Cu) potential energy surfaces include, as does the neutral serine, a large number of conformers, in which a drastic reorganization of the electron density of the serine moiety is observed. This leads to significant changes in the number and strength of the intramolecular hydrogen bonds existing in the neutral serine tautomers. In some cases, a proton is transferred from the carboxylic OH group to the amino group and accordingly, some of the more stable [serine–M]2+ complexes can be viewed as the result of the interaction of the zwiterionic form of serine with the doubly charged metal ion. Whereas the interaction between Ca2+ and serine is essentially electrostatic, that between Cu2+ and serine has a non-negligible covalent character, reflected in larger electron densities at the bond critical points between the metal and the base, in the negative values of the electron density between the two interacting systems, and in much larger Cu2+ than Ca2+ binding energies. More importantly, the interaction with Cu2+ is followed by a partial oxidation of the base, which is not observed when the metal ion is Ca2+. The main consequence is that in Cu2+ complexes a significant acidity enhancement of the serine moiety takes place, which strongly favors the deprotonation of the [serine–Cu]2+ complexes. This is not the case for Ca2+ complexes. Thus, [serine–Ca]2+ complexes, like those formed by urea, thiourea, selenourea, or glycine, should be detected in the gas phase. Conversely, the complexes with Cu2+ should deprotonate spontaneously and therefore only [(serine–H)–Cu]+ monocations should be experimentally accessible.

Ab-Initio Calculation of the β-SiC/Ni Interface

2001 ◽  
Vol 680 ◽  
Author(s):  
A. Blasetti ◽  
G. Profeta ◽  
S. Picozzi ◽  
A. Continenza ◽  
A. J. Freeman
Keyword(s):  
First Principles ◽  
Ab Initio Calculation ◽  
Surface States ◽  
Binding Energies ◽  
Bonding Mechanism ◽  
Covalent Character ◽  
Adsorption Sites ◽  
Barrier Heights ◽  
Adsorption Energies ◽  
The Stability

ABSTRACTWe investigate the adsorption of a Ni monolayer on the β-SiC(001) surface by means of highly precise first-principles all-electron FLAPW calculations. Total energy calculations for the Si- and C-terminated surfaces reveal high Ni adsorption energies, with respect to other metals, confirming the strong reactivity and the stability of the transition metal/SiC interface. These high binding energies, about 7.3-7.4 eV, are shown to be related to strong p-d hybridization, common to both surface terminations and different adsorption sites, which, despite the large mismatch, may stabilize overlayer growth. A detailed analysis of the bonding mechanism, in terms of density of states and hybridization of the surface states, reveals the strong covalent character of the bonding. We also calculate and discuss the Schottky barrier heights at the Ni/SiC junction for both terminations.

Relativity and the periodic table

2020 ◽  
Vol 378 (2180) ◽  
pp. 20190305
Author(s):  
N. C. Pyper
Keyword(s):  
Quantum Mechanics ◽  
Angular Momentum ◽  
Periodic Table ◽  
Relativistic Effect ◽  
Relativistic Quantum ◽  
Binding Energies ◽  
Heavy Elements ◽  
Oxidation States ◽  
Relativistic Quantum Mechanics ◽  
Chemical Behaviour

The periodic table provides a deep unifying principle for understanding chemical behaviour by relating the properties of different elements. For those belonging to the fifth and earlier rows, the observations concerning these properties and their interrelationships acquired a sound theoretical basis by the understanding of electronic behaviour provided by non-relativistic quantum mechanics. However, for elements of high nuclear charge, such as occur in the sixth and higher rows of the periodic table, the systematic behaviour explained by non-relativistic quantum mechanics begins to fail. These problems are resolved by realizing that relativistic quantum mechanics is required in heavy elements where electrons velocities can reach significant fractions of the velocity of light. An essentially non-mathematical description of relativistic quantum mechanics explains how relativity modifies valence electron behaviour in heavy elements. The direct relativistic effect, arising from the relativistic increase of the electron mass with velocity, contracts orbitals of low angular momentum, increasing their binding energies. The indirect relativistic effect causes valence orbitals of high angular momentum to be more effectively screened as a result of the relativistic contraction of the core orbitals. In the alkali and alkaline earths, the s orbital contractions reverse the chemical trends on descending these groups, with heavy elements becoming less reactive. For valence d and f electrons, the indirect relativistic effect enhances the reductions in their binding energies on descending the periodic table. The d electrons in the heavier coinage metals thus become more chemically active, which causes these elements to exhibit higher oxidation states. The indirect effect on d orbitals causes the chemistries of the sixth-row transition elements to differ significantly from the very similar behaviours of the fourth and fifth-row transition series. The relativistic destabilization of f orbitals causes lanthanides to be chemically similar, forming mainly ionic compounds in oxidation state three, while allowing the earlier actinides to show a richer range of chemical behaviour with several higher oxidation states. For the 7p series of elements, relativity divides the non-relativistic p shell of three degenerate orbitals into one of much lower energy with the energies of the remaining two being substantially increased. These orbitals have angular shapes and spin distributions so different from those of the non-relativistic ones that the ability of the 7p elements to form covalent bonds is greatly inhibited. This article is part of the theme issue ‘Mendeleev and the periodic table’.

scholarly journals An accurate single descriptor for ion–π interactions

2020 ◽  
Vol 7 (6) ◽  
pp. 1036-1045 ◽  
Author(s):  
Zhangyun Liu ◽  
Zheng Chen ◽  
Jinyang Xi ◽  
Xin Xu
Keyword(s):  
Electrostatic Interactions ◽  
Quantitative Description ◽  
Physical Nature ◽  
Binding Energies ◽  
Electrostatic Energy ◽  
Π Interactions ◽  
Practical Strategy ◽  
Leading Term ◽  
Level Method ◽  
High Level

Abstract Non-covalent interactions between ions and π systems play an important role in molecular recognition, catalysis and biology. To guide the screen and design for artificial hosts, catalysts and drug delivery, understanding the physical nature of ion–π complexes via descriptors is indispensable. However, even with multiple descriptors that contain the leading term of electrostatic and polarized interactions, the quantitative description for the binding energies (BEs) of ion–π complexes is still lacking because of the intrinsic shortcomings of the commonly used descriptors. Here, we have shown that the impartment of orbital details into the electrostatic energy (coined as OEE) makes an excellent single descriptor for BEs of not only spherical, but also multiply-shaped, ion–π systems, highlighting the importance of an accurate description of the electrostatic interactions. Our results have further demonstrated that OEEs from a low-level method could be calibrated to BEs from a high-level method, offering a powerful practical strategy for an accurate prediction of a set of ion–π interactions.

Angle resolved electron spectra from collisions of doubly charged noble gas ions with a metal surface

1989 ◽  
Vol 211-212 ◽  
pp. A115
Author(s):  
P.A.A.F. Wouters ◽  
P.A.Zeijlmans Van Emmichoven ◽  
A. Niehaus
Keyword(s):  
Metal Surface ◽  
Noble Gas ◽  
Electron Spectra ◽  
Doubly Charged

scholarly journals Effect of Lysyllysine on non-covalent hybridization of single walled carbon nanotube by single-stranded DNA homodimer: in silico approach

2019 ◽  
Vol 9 (4) ◽  
pp. 315-321
Author(s):  
Fateme Bagherolhashemi ◽  
Mohammad Reza Bozorgmehr ◽  
Mohammad Momen-Heravi
Keyword(s):  
Molecular Dynamics ◽  
Carbon Nanotube ◽  
Electrostatic Interactions ◽  
Membered Ring ◽  
Binding Energies ◽  
Van Der Waals Interactions ◽  
Dynamics Simulation ◽  
Quantum Calculations ◽  
Single Walled Carbon Nanotube ◽  
Sensor Properties

Abstract In this work, the interactions between adenine–adenine di-nucleotide (DA2N) and carbon nanotube (CNT) in the presence of Lysyllysine (LL) was studied by the molecular dynamics simulation. Different carbon nanotubes including (5.5), (6.6) and (7.7) were used to investigate the effect of CNT type. The binding energies were calculated using the molecular mechanics-Poisson Bolzmann surface area method. The results showed that the contribution of the van der Waals interactions between DA2N and CNT was greater than that of the electrostatic interactions. The LL significantly enhanced the electrostatic interactions between the DA2N and CNT (6.6). The quantum calculations revealed that the sensor properties of the DA2N were not significantly affected by the CNT and LL. However, the five-membered ring of adenine played a more important role in the sensing properties of the DA2N. The obtained results are consistent with the previous experimental observations that can help to understand the molecular mechanism of the interaction of DA2N with CNT. Graphic abstract

Noble gas–selenium molecular species: A theoretical investigation of FNgSe− (Ng=He–Xe)

2009 ◽  
Vol 470 (1-3) ◽  
pp. 49-53 ◽  
Author(s):  
Stefano Borocci ◽  
Nicoletta Bronzolino ◽  
Felice Grandinetti
Keyword(s):  
Theoretical Investigation ◽  
Molecular Species ◽  
Noble Gas
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