PROBING THE INTERPLAY BETWEEN MULTIPLICITY AND IONICITY OF THE CHEMICAL BOND

2011 ◽  
Vol 10 (04) ◽  
pp. 471-482 ◽  
Author(s):  
DARIUSZ SZCZEPANIK ◽  
JANUSZ MROZEK
Keyword(s):  
Chemical Bond ◽  
Population Analysis ◽  
Atomic Charge ◽  
Numerical Results ◽  
Basis Set ◽  
Chemical Bonds ◽  
Bond Multiplicity ◽  
Bond Covalency ◽  
Type Bond

A new bond multiplicity measure based on the Wiberg-type bond covalency index and the atomic charge from population analysis is presented. Heuristically derived formulas allow one to evaluate the character of the chemical bond, especially its ionicity degree. Numerical results at RHF/ROHF theory level demonstrate that full multiplicities of typical chemical bonds are close to formal orders and their basis set dependence is inconsiderable, especially for highly polarized chemical bonds.

Structure and bonding in square-planar chalcogen rings

1992 ◽  
Vol 70 (2) ◽  
pp. 348-352 ◽  
Author(s):  
Leif J. Saethre ◽  
Odd Gropen
Keyword(s):  
Potential Model ◽  
Population Analysis ◽  
Atomic Charge ◽  
Molecular Structures ◽  
Basis Set ◽  
Single Bond ◽  
Bond Lengths ◽  
Square Planar ◽  
Structure And Bonding ◽  
D Orbitals

The molecular structures of square-planar X42+, X4+, and X4 (X = S, Se, Te) have been calculated using the effective core potential model. For X42+ the agreement between experimental and calculated values is excellent provided that d orbitals are included in the basis set. For the hypothetical molecules X4+ and X4 the bond lengths are found to increase dramatically as one and, subsequently, two electrons are added to the systems. Extensive population analysis shows that this increase is almost exclusively due to loss of bonding in the π system, whereas the bonding in the σ system remains relatively unaltered. These results make it possible to predict covalent single bond radii for S, Se, and Te for which the influence of π repulsion is removed. From the calculated variation of bond lengths with atomic charge, bond lengths are predicted for a series of planar disulphide rings. Keywords: structure, bonding, chalcogen, theoretical, ECP.

scholarly journals Fast Atomic Charge Calculation for Implementation into a Polarizable Force Field and Application to an Ion Channel Protein

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Raiker Witter ◽  
Margit Möllhoff ◽  
Frank-Thomas Koch ◽  
Ulrich Sternberg
Keyword(s):  
Force Field ◽  
Influenza A ◽  
Transmembrane Domain ◽  
Population Analysis ◽  
3D Structure ◽  
Atomic Charge ◽  
Basis Set ◽  
Atomic Charges ◽  
Molecular Mechanics Calculations ◽  
Activated State

Polarization of atoms plays a substantial role in molecular interactions. Class I and II force fields mostly calculate with fixed atomic charges which can cause inadequate descriptions for highly charged molecules, for example, ion channels or metalloproteins. Changes in charge distributions can be included into molecular mechanics calculations by various methods. Here, we present a very fast computational quantum mechanical method, the Bond Polarization Theory (BPT). Atomic charges are obtained via a charge calculation method that depend on the 3D structure of the system in a similar way as atomic charges ofab initiocalculations. Different methods of population analysis and charge calculation methods and their dependence on the basis set were investigated. A refined parameterization yielded excellent correlation ofR=0.9967. The method was implemented in the force field COSMOS-NMR and applied to the histidine-tryptophan-complex of the transmembrane domain of the M2 protein channel of influenza A virus. Our calculations show that moderate changes of side chain torsion angleχ1and small variations ofχ2of Trp-41 are necessary to switch from the inactivated into the activated state; and a rough two-side jump model of His-37 is supported for proton gating in accordance with a flipping mechanism.

Electron Pairing and Chemical Bonds. Physical Meaning of Effective Pairs

1994 ◽  
Vol 59 (12) ◽  
pp. 2567-2578 ◽  
Author(s):  
Robert Ponec ◽  
Filip Uhlík
Keyword(s):  
Density Distribution ◽  
Electron Density ◽  
Physical Meaning ◽  
Electron Density Distribution ◽  
Mutual Coupling ◽  
Population Analysis ◽  
Point Of View ◽  
Chemical Bonds ◽  
Conditional Probabilities ◽  
Electron Pairing

The physical meaning of the so-called effective pairs which have been introduced recently within the formalism of pair population analysis is discussed using the analysis of conditional probabilities of electron density distribution for electron 1 with the reference electron fixed in a certain point 2. It is demonstrated that from the point of view of the mutual coupling of electron motions, the effective pairs behave analogously to singlet pairs. Based on this finding, effective pairs can be interpreted as the fraction of singlet pairs that is directly involved in bonding.

scholarly journals C2: An Asymmetric Specie ?

2020 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Chemical Bond ◽  
Raman Spectra ◽  
Density Functional ◽  
Functional Approach ◽  
Ir And Raman Spectra ◽  
Basis Set ◽  
Ir And Raman

<p> The present work is another contribution to a better understanding of the chemical bond in C<sub>2</sub>. Several density functional approach/basis set provided calculated IR and Raman spectra with simultaneous active bands. Hence, the hypothesis of electronic asymmetry in C<sub>2</sub> [1] was reinforced. </p>

scholarly journals Effect of Doping on the Photoelectric Properties of Borophene

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Chunhong Zhang ◽  
Zhongzheng Zhang ◽  
Wanjun Yan ◽  
Xinmao Qin
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Population Analysis ◽  
Covalent Bond ◽  
Infrared Light ◽  
Chemical Bonds ◽  
Mulliken Population Analysis ◽  
Mulliken Population ◽  
Photoelectric Properties ◽  
Effect Of Doping

Borophene is a new type of two-dimensional material with a series of unique and diversified properties. However, most of the research is still in its infancy and has not been studied in depth. Especially in the field of semiconductor optoelectronics, there is no related research on the modulation of photoelectric properties of borophene. In this work, we focus on the effect of doping on the photoelectric properties of borophene by using the first-principles pseudopotential plane wave method. We calculate the geometric structure, electronic structure, Mulliken population analysis, and optical properties of impurity (X = Al, Ga) doped α-sheet borophene. The results show that α-sheet borophene is an indirect band gap semiconductor with 1.396 eV. The band gap becomes wider after Al and Ga doping, and the band gap values are 1.437 eV and 1.422 eV, respectively. Due to the orbital hybridization between a small number of Al-3p electrons and Ga-4p state electrons and a large number of B 2p state electrons near the Fermi level, the band gap of borophene changes and the peak value of the electron density of states reduces after doping. Mulliken population analysis shows that the B0-B bond is mainly covalent bond, but there is also a small amount of ionic bond. However, when the impurity X is doped, the charge transfer between X and B atoms increases significantly, and the population of the corresponding X-B bonds decreases, indicating that the covalent bond strength of the chemical bonds in the doped system is weakened, and the chemical bonds have significant directionality. The calculation of optical properties shows that the static dielectric constant of the borophene material increases, and the appearance of a new dielectric peak indicates that the doping of Al and Ga can enhance the ability of borophene to store electromagnetic energy. After doping, the peak reflectivity decreases and the static refractive index n0 increases, which also fills the gap in the absorption of red light and infrared light by borophene materials. The research results provide a basis for the development of borophene materials in the field of infrared detection devices. The above results indicate that doping can modulate the photoelectric properties of α-sheet borophene.

System Analysis and Control of the Influence of a Mixed Type of Chemical Bond in Substances and Materials on their Structure and Properties

2021 ◽  
Vol 887 ◽  
pp. 551-556
Author(s):  
O.S. Sirotkin ◽  
R.O. Sirotkin ◽  
M.Yu. Perukhin
Keyword(s):  
Chemical Bond ◽  
System Analysis ◽  
Energy Structure ◽  
Chemical Bonds ◽  
Computer Programme ◽  
Structure And Properties ◽  
Materials Development ◽  
Metallic Material ◽  
Bond Type ◽  
And Control

Nowadays, a lot of information on structure and properties of a wide variety of substances and materials has been accumulated. Yet, there is a lack of systemic universal approaches to assessing their structure and properties, including developing the effective approaches for monitoring and analysing various materials. It is of special interest in this respect to assess the effects of the chemical bond type on structure and properties of substances and materials. However, searching for necessary data on the effects of chemical bonds on structure of substances and materials is a rather laborious process. The authors, relying on the intermediate nature of chemical bonds of compounds of elements in any metallic and non-metallic material, as well as the system of chemical bonds and compounds developed by them in the form of a “Chemical Triangle”, produced an algorithm for creating a computer programme. It implies systematising of the database on the effect of chemical bond type on its length and energy, structure and various physicochemical and mechanical properties of homo-and heteronuclear compounds and materials. Development of such a specialised computer programme greatly simplifies this process, providing more efficient analysis and control of materials.

From Atomic Orbitals to Molecular Orbitals and Chemical Bonds

2020 ◽  
pp. 150-187
Author(s):  
Jochen Autschbach
Keyword(s):  
Hydrogen Molecule ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Basis Set ◽  
Orbital Method ◽  
Chemical Bonds ◽  
Atomic Orbitals ◽  
Hartree Fock ◽  
Generalized Matrix

It is shown how an aufbau principle for atoms arises from the Hartree-Fock (HF) treatment with increasing numbers of electrons. The Slater screening rules are introduced. The HF equations for general molecules are not separable in the spatial variables. This requires another approximation, such as the linear combination of atomic orbitals (LCAO) molecular orbital method. The orbitals of molecules are represented in a basis set of known functions, for example atomic orbital (AO)-like functions or plane waves. The HF equation then becomes a generalized matrix pseudo-eigenvalue problem. Solutions are obtained for the hydrogen molecule ion and H2 with a minimal AO basis. The Slater rule for 1s shells is rationalized via the optimal exponent in a minimal 1s basis. The nature of the chemical bond, and specifically the role of the kinetic energy in covalent bonding, are discussed in details with the example of the hydrogen molecule ion.

Surface Structure of Sulfur Coated GaAs

1989 ◽  
Vol 163 ◽  
Author(s):  
Yoshihisa Fujisaki ◽  
Shigeo Goto
Keyword(s):  
Electron Beam ◽  
Surface Structure ◽  
Chemical Bond ◽  
Photoelectron Spectroscopy ◽  
Strong Dependence ◽  
High Energy ◽  
Chemical Bonds ◽  
High Energy Electron ◽  
X Ray ◽  
Beam Diffraction

AbstractSurface structure of (NH4)2S treated GaAs. is investigated using PL (PhotoLuminescence), XPS (X-ray Photoelectron Spectroscopy) and RHEED (Reflection of High Energy Electron beam Diffraction). The data taken with these techniques show the strong dependence upon the crystal orientations coming from the stabilities of chemical bonds of Ga-S and As-S on GaAs crystals. The greater enhancement of PL intensity, the clearer RHEED patterns and the smaller amount of oxides on (111)A than (111)B implies the realization of a more stable structure composed mainly of the Ga-S chemical bond.

Kinetics of Potassium Dihydrogen Phosphate Single-Crystal Growth Mapped by the Chemical Bond Simulation

2012 ◽  
Vol 554-556 ◽  
pp. 31-34 ◽  
Author(s):  
Xu Zhang ◽  
De Xiang Jia
Keyword(s):  
Chemical Bond ◽  
Crystal Morphology ◽  
Potassium Dihydrogen Phosphate ◽  
Dihydrogen Phosphate ◽  
Chemical Bonds ◽  
Potassium Dihydrogen ◽  
Solution Interface ◽  
Shape Controlled ◽  
Kinetics Of ◽  
Kdp Crystals

A chemical bond simulation was proposed to quantitatively calculate the growth rate from the kinetic model of the crystal-solution interface. When this approach was applied to the cases of potassium dihydrogen phosphate (KDP) crystals grown from the solution with different surpersaturation, the growth behaviors of KDP crystals were predicted and the calculated results were consistent with the experimental data. These results demonstrate that regulating the distribution of the chemical bonds between the crystal and solution interfaces can effectively control the crystal morphology. Seeding experiments with the chemical bond simulation may have significant potential towards the development of shape-controlled growth with defined conditions.

Electron Pairing and Chemical Bonds

1994 ◽  
Vol 59 (3) ◽  
pp. 505-516 ◽  
Author(s):  
Robert Ponec
Keyword(s):  
Molecular Structure ◽  
Quantum Chemical ◽  
Population Analysis ◽  
Structural Formula ◽  
Chemical Bonds ◽  
Electron Pairing ◽  
Theoretical Evidence ◽  
Simple Molecules ◽  
Classical Picture

The recently proposed population analysis of pair densities is applied to the investigation of molecular structure of several simple molecules. The values of pairon populations straightforwardly reproduce the classical structural formula including the multiplicity of the bonds and provide thus the so far missing link between quantum chemical and Lewis's classical picture of bonding. As demonstrated, the formalism of the proposed approach provides strong theoretical evidence for the frequently expected but so far elusive role of electron pairing in chemical bonding.

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