scholarly journals The formation of hydride bonds in cationic complexes of nBeH2•••mX with n=1 or 2, m=1 or 2 and X = Li+ or Na+

2014 ◽  
Vol 79 (11) ◽  
pp. 1413-1420
Author(s):  
Boaz Oliveira
Keyword(s):  
Charge Density ◽  
Intermolecular Interaction ◽  
Infrared Spectra ◽  
Interaction Strength ◽  
Covalent Character ◽  
Topological Parameters ◽  
Density Concentration ◽  
Optimized Geometries

Through the BH and HLYP/6-31G(d,p) calculations, the optimized geometries and topological parameters of the BeH2???Na+, BeH2???Li+, 2BeH2???Na+, BeH2???2Na+, 2BeH2???Li+ and BeH2???2Li+ cationic complexes were obtained. One or two hydride bonds formed simultaneously on the same hydride center. The analysis of the infrared spectra revealed the existence of red-shifts and blue-shifts on the BeH bonds, whose effects are not in line with the intermolecular interaction strength determined by means of the supermolecule approach. The QTAIM calculations were developed to measure the charge density concentration on the H???Na+ and H???Li+ hydride bonds. Moreover, the covalent character of these interactions interpreted on the basis of the ratio between kinetic and potential electronic energies was also examined.

The covalence and infrared spectra of cationic hydrogen bonds and dihydrogen bonds

2014 ◽  
Vol 13 (07) ◽  
pp. 1450060 ◽  
Author(s):  
Boaz G. Oliveira
Keyword(s):  
Hydrogen Bonds ◽  
Bond Length ◽  
Infrared Spectra ◽  
Theoretical Study ◽  
Interaction Strength ◽  
Covalent Character ◽  
Frequency Shifts ◽  
Dihydrogen Bonds ◽  
Length Reduction ◽  
Ethyl Cation

A theoretical study of hydrogen bonds and dihydrogen bonds formed by ethyl cation, hydrocarbons and magnesium hydride is presented with calculations performed at the BHandHLYP/6-31G(d,p) level of theory. The structural results and IR analyses demonstrated great insights, mainly the strengthening and weakness of the CC bond of the ethyl cation and π or pseudo-π bonds, respectively. The interaction strength was measured through the supermolecule as well as by means of additional approaches. The QTAIM calculations were applied to characterize not only the intermolecular interactions but specifically the covalent character in the H + ⋯ π, H + ⋯ pseudo-π and H + ⋯ H contacts. The NBO calculations were useful to interpret the polarization on the CC bond and whether this effect is related with the bond length reduction as well as increase of charge density and frequency shifts.

MODELING VIBRATIONAL SPECTRA USING THE SELF-CONSISTENT CHARGE DENSITY-FUNCTIONAL TIGHT-BINDING METHOD II: INFRARED SPECTRA

2005 ◽  
Vol 04 (spec01) ◽  
pp. 639-655 ◽  
Author(s):  
HENRYK A. WITEK ◽  
KEIJI MOROKUMA ◽  
ANNA STRADOMSKA
Keyword(s):  
Charge Density ◽  
Infrared Spectra ◽  
Density Functional ◽  
Organic Molecules ◽  
Tight Binding ◽  
Additional Term ◽  
Functional Theory ◽  
Molecular Electron ◽  
Self Consistent ◽  
Energy Formula

We present an extended self-consistent charge density-functional tight-binding (SCC-DFTB) method that allows for computing vibrational infrared spectra. The extension is based on introducing an additional term in the SCC-DFTB energy formula that describes effectively the interaction of external electric field with molecular electron density distribution. The extended SCC-DFTB method is employed to model vibrational infrared spectra of 16 organic molecules. The calculated spectra are compared to experiment and to spectra obtained with density functional theory. For most of the molecules, the SCC-DFTB method reproduces the experimental spectra in a very satisfactory manner. We discuss the drawbacks and possible applications of this new scheme.

Analysis of intramolecular hydrogen bonding in terms of the topological properties of the charge density. The protonated fluoroacetones

1986 ◽  
Vol 64 (10) ◽  
pp. 2042-2047 ◽  
Author(s):  
Sai Cheng Choi ◽  
Russell J. Boyd
Keyword(s):  
Hydrogen Bonding ◽  
Charge Density ◽  
Intramolecular Hydrogen Bonding ◽  
Basis Set ◽  
Topological Properties ◽  
Strong Basis ◽  
Bonding Interaction ◽  
Equilibrium Structures ◽  
Intramolecular Hydrogen ◽  
Optimized Geometries

A new method for the analysis of intramolecular hydrogen bonding is proposed and applied to the equilibrium structures of the protonated fluoroacetones. The method, based on a theory of molecular structure due to Bader, uses the topological properties of the charge density to elucidate the types of interactions within a molecule of interest. The calculations show a strong basis set dependence. In particular, the STO-3G optimized geometries exhibit intramolecular hydrogen bonding between a fluorine substituent and the carbonyl proton, whereas some calculations with geometries optimized at the 4-31G and 6-31G* levels indicate a direct bonding interaction between the fluorine and oxygen atoms. Two types of catastrophe point, namely conflict and bifurcation, are possible in protonated monofluoroacetone. Only the latter was located in the present calculations.

Analysis of charge density in nonaaquagadolinium(III) trifluoromethanesulfonate – insight into GdIII—OH2 bonding

2020 ◽  
Vol 76 (4) ◽  
pp. 572-580
Author(s):  
Rafał Janicki ◽  
Przemysław Starynowicz
Keyword(s):  
Charge Density ◽  
Density Functional ◽  
Natural Bond Orbital ◽  
Density Functional Theory Calculations ◽  
Charge Density Distribution ◽  
Functional Theory ◽  
Topological Parameters ◽  
Covalent Contribution ◽  
Experimental Charge Density ◽  
Insight Into

The experimental charge-density distribution in [Gd(H2O)9](CF3SO3)3 has been analysed and compared with the theoretical density functional theory calculations. Although the Gd—OH2 bonds are mainly ionic, a covalent contribution is detectable when inspecting both the topological parameters of these bonds and the natural bond orbital results. This contribution originates from small electron transfer from the lone pairs of oxygen atoms to empty 5d and 6s spin orbitals of Gd3+.

Charge density investigations on [2,2]-paracyclophane – in data we trust

2015 ◽  
Vol 71 (1) ◽  
pp. 10-19 ◽  
Author(s):  
Hilke Wolf ◽  
Mads R. V. Jørgensen ◽  
Yu-Sheng Chen ◽  
Regine Herbst-Irmer ◽  
Dietmar Stalke
Keyword(s):  
Charge Density ◽  
Structural Parameters ◽  
Topological Analysis ◽  
Topological Parameters ◽  
Different Temperatures ◽  
Density Analysis ◽  
Multipole Refinement ◽  
Global Data ◽  
Data Quality Indicators

Four datasets on [2,2]-paracyclophane were collected in-house and at the Advanced Photon Source at two different temperatures for charge density investigation. Global data quality indicators such as high resolution, highI/σ(I) values, low mergingRvalues and high multiplicity were matched for all four datasets. The structural parameters did not show significant differences, but the synchrotron data depicted deficiencies in the topological analysis. In retrospect these deficiencies could be assigned to the low quality of the innermost data, which could have been identified bye.g.mergingRvalues for only these reflections. In the multipole refinement these deficiencies could be monitored usingDRK-plotand residual density analysis. In this particular example the differences in the topological parameters were relatively small but significant.

scholarly journals Charge density studies of multicentre two-electron bonding of an anion radical at non-ambient temperature and pressure

IUCrJ ◽  
2021 ◽  
Vol 8 (4) ◽  
Author(s):  
Valentina Milašinović ◽  
Krešimir Molčanov ◽  
Anna Krawczuk ◽  
Nikita E. Bogdanov ◽  
Boris A. Zakharov ◽  
...  
Keyword(s):  
Charge Density ◽  
Radical Anion ◽  
Anion Radical ◽  
Ambient Pressure ◽  
Covalent Character ◽  
Charge Densities ◽  
Semiquinone Radicals ◽  
Temperature And Pressure ◽  
Covalent Interactions ◽  
Resolution Data

The variation of charge density of two-electron multicentre bonding (pancake bonding) between semiquinone radicals with pressure and temperature was studied on a salt of 5,6-dichloro-2,3-dicyanosemiquinone radical anion (DDQ) with 4-cyano-N-methylpyridinium cation (4-CN) using the Transferable Aspheric Atom Model (TAAM) refinement. The pancake-bonded radical dimers are stacked by non-bonding π-interactions. With rising pressure, the covalent character of interactions between radicals increases, and above 2.55 GPa, the electron density indicates multicentric covalent interactions throughout the stack. The experimental charge densities were verified and corroborated by periodic DFT computations. The TAAM approach has been tested and validated for atomic resolution data measured at ambient pressure; this work shows this approach can also be applied to diffraction data obtained at pressures up to several gigapascals.

scholarly journals Условия коалесценции объемных нанопузырьков

2020 ◽  
Vol 46 (14) ◽  
pp. 25
Author(s):  
C.И. Кошоридзе
Keyword(s):  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Practical Importance ◽  
Energy Approach ◽  
Radius Ratio ◽  
Simplified Model ◽  
Density Concentration

The paper considers the coalescence of two bulk nanobubbles with significantly different radii. The study of this issue is of practical importance,since coalescence is an undesirable process: nanobubbles lose their unique properties as they grow larger. In a simplified model of charged nanobubbles based on the energy approach, it is shown that, in contrast to surface nanobubbles , for bulk nanobubbles coalescence can occur at certain values of surface charge density, concentration , and radius ratio.

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