Anna Pomogaeva - Academia.edu (original) (raw)
Papers by Anna Pomogaeva
Journal of Physical Chemistry A, Apr 16, 2021
Electronic structures and thermodynamic characteristics of chain inorganic group 13-15 oligomers ... more Electronic structures and thermodynamic characteristics of chain inorganic group 13-15 oligomers [H2MEH2]n (M = B, Al, Ga, E = P, As; n = 4-15) are presented. Donor-acceptor interaction with both Lewis acids and Lewis bases effectively stabilizes chain isomers with respect to spontaneous cyclization and significantly changes their electronic structure.
Zeitschrift für anorganische und allgemeine Chemie, Feb 2, 2021
Solid state structures of five new molecular complexes of SbI3 with Py have been determined by si... more Solid state structures of five new molecular complexes of SbI3 with Py have been determined by single crystal X-ray structural analysis. In all complexes, all antimony atoms adopt a pseudooctahedral coordination geometry, which is completed by additional Sb•••I contacts shorter than sum of van der Waals radii, with I-Sb•••I angles close to 180º. Analysis of the electrostatic potentials, the orbital interactions and topological analysis indicate that these contacts are due to the presence of Sb•••I pnictogen bonds. The first example of three pnictogen bonds of SbI3 is reported.
Journal of Physical Chemistry B, Dec 13, 2013
Polyhedron, 2019
Molecular structures of two new SbCl 3-Py complexes, (SbCl 3) 4 Py 4 and (SbCl 3) 3 Py 5 , in the... more Molecular structures of two new SbCl 3-Py complexes, (SbCl 3) 4 Py 4 and (SbCl 3) 3 Py 5 , in the solid state have been determined by single crystal X-ray diffraction. In both complexes all Sb atoms adopt a pseudo-octahedral coordination geometry which is completed by additional Sb•••Cl contacts shorter than sum of van der Waals radii, with Cl-Sb•••Cl angles close to 180º. These contacts indicate the presence of Sb•••Cl pnictogen bonding. To reveal its nature, the DFT calculations were performed followed by the analyses of the electrostatic potentials, the orbital interactions and topological analysis.
Chemistry: A European Journal, Oct 28, 2020
Supporting information (SI) for this article is given via a link at the end of the document.
Journal of Chemical Theory and Computation, Oct 28, 2011
The performance in describing hydration free energies of a broad class of neutral, cationic, and ... more The performance in describing hydration free energies of a broad class of neutral, cationic, and anionic solutes is tested for the recently proposed FESR (Field-Extremum Short-Range) implicit solvation model for interactions between the solute and nearby water molecules, as taken in conjunction with the previously developed SS(V)PE (Surface and Simulation of Volume Polarization for Electrostatics) dielectric continuum model for long-range interactions with bulk water. The empirical FESR model mainly describes soluteÀwater hydrogen bonding interactions by correlating them with the maximum and minimum values of the electric field produced by the solute at the surface of the cavity that excludes solvent. A preliminary report showed that, with only four adjustable parameters, the FESR model, in conjunction with SS(V)PE, can produce hydration energies comparable to the best analogous efforts in the literature that utilized many more parameters. Here, the performance of the FESR model is more fully documented in several respects. The dependence on the underlying quantum mechanical method used to treat the internal electronic structure of the solute is tested by comparing uncorrelated HartreeÀFock to correlated density functional calculations and by comparing a modest sized to a large basis set. The influence of cavity size is studied in connection with an isodensity contour construction of the cavity. The sensitivity of the results to the parameters in the FESR model is considered, and it is found that the dependence on the electric field strength is quite nonlinear, with an optimum exponent consistently in the range of 3 to 4. Overall, it is concluded that the FESR model shows considerable utility for improving the accuracy of implicit models of aqueous solvation.
Physical Chemistry Chemical Physics, 2016
A DFT study of thermal decomposition mechanisms of [M(NH 2 BH 3) 2 ] 4 clusters with M = Mg, Ca, ... more A DFT study of thermal decomposition mechanisms of [M(NH 2 BH 3) 2 ] 4 clusters with M = Mg, Ca, and Sr is presented. Multi-step reaction pathways leading to elimination of the first H 2 molecule are explored at the M06/TZVP level of theory. For all studied M, the clusters adopt similar structures and exhibit similar transformations along the reaction pathways. Their activation energies decrease in the order Mg o Ca r Sr. Four metal atoms in the cluster form a rigid planar construction that is found to be nearly unchanged during all transformations. Cleavage of the B-H bond in the environment of alkaline-earth metal atoms leads to the ''capture'' of the released H atom by neighboring metal atoms with the formation of a M 3 H moiety. While the activation energies for the cleavage of H dÀ can be as low as 14.3, 22.6 and 23.3 kcal mol À1 for M = Mg, Ca and Sr, respectively, barriers for the subsequent cleavage of H d+ via destruction of the M 3 H moiety are about twice larger.
International Journal of Quantum Chemistry, May 1, 2009
Photophysical properties of polyethylene structures embedding aromatic fragments (benzene, anthra... more Photophysical properties of polyethylene structures embedding aromatic fragments (benzene, anthracene, 4-dicyanomethylene-4H-pyran, tryptophan, and estradiol) responsible for existence lowest electronically excited states were studied by new technique involving the elongation method applied to quantum-chemical calculations. Absorption spectra and some photophysical properties were obtained. The comparison between the elongation and the conventional calculations was made, and it is shown that the elongation method is a powerful tool to determine the excited states as well as optical properties for large systems.
Journal of Physical Chemistry A, Feb 3, 2009
The statistical quantum chemical/molecular dynamical method is developed and employed to reproduc... more The statistical quantum chemical/molecular dynamical method is developed and employed to reproduce optical spectra. This technique includes quantum-mechanical calculations on energy states and photophysical properties of molecular conformers obtained during molecular dynamical simulation. Polycyclic organic molecule estradiol surrounded by solvent particles and protein structure including tryptophan fragment under thermodynamical conditions are considered. A wide absorption spectrum over several excited electronic states of estradiol is constructed. First longwave absorption band of tryptophan-cage mini protein is built involving the elongation method. These statistical spectra reflect the main features of the corresponding experimental ones.
Russian Journal of General Chemistry, Apr 1, 2023
Chemical Physics Letters, Jul 1, 2011
A novel model of short-range contributions to hydration free energies is introduced for use with ... more A novel model of short-range contributions to hydration free energies is introduced for use with dielectric continuum treatment of long-range bulk electrostatics. The empirical model invokes extrema of the solute normal electric field at the cavity surface that nominally separates solute from solvent. It involves only a small handful of adjustable parameters, which are fitted to experimental data on a large collection of neutral and ionic solutes. The results show mean unsigned errors from experiment of only 0.9kcal/mol for neutrals and 2.4kcal/mol for ions, which are comparable to the best analogous previous efforts that utilize many more parameters.
![Research paper thumbnail of The effect of terminal substituents on the electronic properties of rod-shaped [HGaNH]n oligomers](https://attachments.academia-assets.com/108633290/thumbnails/1.jpg)
](Physical Chemistry Chemical Physics, 2016
The effect of electron-donating and electron-withdrawing terminal groups on the electronic struct... more The effect of electron-donating and electron-withdrawing terminal groups on the electronic structure of the rod-shaped X 3 [HGaNH] n Y 3 or needle-shaped XGa[HGaNH] n NY oligomers (X, Y = H, CH 3 , F, CF 3 ; n = 9, 30 and 114) was computationally studied at the B3LYP/SVP level of density functional theory. While the needle-shaped oligomers exhibit moderate variability in the electronic structure upon changing the terminal substituents X and Y, the energy gap of long rod-shaped oligomers varies within 2 eV. For oligomers with n = 114, F 3 [HGaNH] n (CH 3) 3 exhibits the largest HOMO-LUMO gap of 2.91 eV, while (CH 3) 3 [HGaNH] n F 3 has the smallest gap of 0.94 eV.
Journal of Physical Chemistry A, Jul 5, 2013
Implicit solvation models provide a very efficient means to estimate solvation energies. For exam... more Implicit solvation models provide a very efficient means to estimate solvation energies. For example, dielectric continuum models are commonly used to obtain the long-range electrostatic interactions. These may be parametrized to also include in some average manner short-range interactions such as dispersion and exchange, but it is preferable to instead develop additional implicit models specifically designed for the shortrange interactions. This work proposes new models for dispersion and exchange interactions between solute and solvent by adapting approaches previously developed for treatment of gas-phase intermolecular forces. The new models are formulated in terms of the charge densities of the solutes and use only three adjustable parameters. To illustrate the performance of the models, electronic structure calculations are reported for a large number of solutes in two nonpolar solvents where short-range interactions dominate and different balances pertain between attractive dispersion and repulsive exchange contributions. After empirical optimization of the requisite parameters, it is found that the errors compared to experimental solvation free energies are only about 0.4 kcal/mol on average, which is better than previous approaches in the literature that invoke many more parameters.
Nucleation and Atmospheric Aerosols, 2019
Using the methods of scanning electron microscopy (Scanning Electron Microscope-SEM) and X-ray ph... more Using the methods of scanning electron microscopy (Scanning Electron Microscope-SEM) and X-ray photoelectron spectroscopy (XPS), changes in the atomic structure and chemical state of multi-walled carbon nanotubes (MWCNTs) due to the action of ion beams of argon and helium with different irradiation parameters were investigated. Based on the experimental XPS and XANES (X-ray absorption near edge structure) data, as well as theoretical data, changes in the density of electronic states near the Fermi level in MWCNTs after ion-beam action were analyzed. It is shown that the use of beams of argon and helium ions can be used for directional functionalization of MWCNTs and applications in the chemical and petrochemical industries.
Springer eBooks, 2020
Synthetic approaches, structures, and reactivity of group 13–15 needle-shaped oligomers have been... more Synthetic approaches, structures, and reactivity of group 13–15 needle-shaped oligomers have been reviewed. Computational studies reveal that needle-shaped oligomers are more stable than fullerene-like isomers for all 13–15 pairs. Formation of such oligomers in the gas phase is energetically favorable and feasible from the thermodynamic point of view. However, many competitive reaction pathways are kinetically possible which leads to cascade of reactions and different reaction products. A systematic study of the various effects of structural variations on the electronic properties of Ga-N-based nanorods has been performed. On the basis of DFT computations, we demonstrate that terminal groups have a crucial impact on the electronic properties of the rod-shaped [RGaNH]3n (R=H, CH3) oligomers. Oligomers capped with GaR and NH groups adopt almost periodic structure in which terminal groups affect only the very edges of the oligomer. The band gap energy of the [HGaNH]3n+1 is defined by states localized at the different ends of the oligomer. The value of the band gap is converging fast with increase of n, and for n = 38 it is about 93% of the value of the band gap of the [HGaNH]3∞ polymer. In contrast, termination of the [HGaNH]3n rod-shaped oligomer by saturation of dangling bonds with H or CH3 groups destroys the periodic pattern and increases the number of states, localized at the ends of the oligomer. This way of termination is characterized by systematic change in structural parameters of the oligomer and near exponential decrease of the band gap energy with the oligomer length. The band gap energy for the rod-shaped oligomer of 10 nm of length (n = 38) amounts to only 27% of the value for the band gap of the [HGaNH]3∞ polymer. Substitution of Ga atoms by Al and In has also been considered. Absorption spectra undergo a red shift if Ga atoms are replaced by In atoms and a small blue shift if Ga atoms are replaced by Al atoms. The effect of electron-donating and electron-withdrawing terminal groups (H, CH3, F, CF3) on a dipole moment and energy gap values is found to be significant. The band gap energy of long tube-shaped Ga-N-based oligomers can be tuned within 2 eV by changing the substituents at the ends of the oligomer. A combined effect of all considered factors, substituent groups variations, rod’s elongation, and the way of ends’ termination, can help to vary energy gap of the [HGaNH]3n rod-shaped oligomer within the range 1–7 eV. Potential applications and further directions are also discussed.
Nucleation and Atmospheric Aerosols, 2007
ABSTRACT A method to build band structure of polymers from oligomer calculations has been develop... more ABSTRACT A method to build band structure of polymers from oligomer calculations has been developed. The correspondence between calculated energies of finite molecular chain and wave vector is obtained by projecting molecular orbitals (Mos) on the model Bloch functions. On the example of polydiacetylene, the reliability of the method for different computational methods (Hartree-Fock (HF), Density Functional Theory (DFT) with different basis sets) is shown.
Journal of Computational Chemistry, Jul 5, 2021
Energetic effects of solvation of SbF5, SbCl5, and 21 group 13 Lewis acids (LA) and their molecul... more Energetic effects of solvation of SbF5, SbCl5, and 21 group 13 Lewis acids (LA) and their molecular complexes with acetonitrile and pyridine are evaluated using SMD approach. Compared to the gas phase, solvation increases the stability of boron‐ and aluminum‐containing complexes but decreases the stability of gallium and indium‐containing homologs due to larger solation energies of free LA. New Lewis acidity scales, based on the Gibbs energy of dissociation of the molecular complexes LA·pyridine and LA·acetonitrile in the gas phase, in benzene and acetonitrile solutions, are proposed.
![Research paper thumbnail of Strong Dependence of Structural and Electronic Properties of Rod-Shaped [RGaNH]<sub>3<i>n</i></sub> (R = H, CH<sub>3</sub>) Oligomers on Terminal Groups](https://attachments.academia-assets.com/108633335/thumbnails/1.jpg)
](Journal of Physical Chemistry C, Jul 13, 2015
On the basis of DFT calculations, we demonstrate that terminal effects have a crucial impact on e... more On the basis of DFT calculations, we demonstrate that terminal effects have a crucial impact on electronic properties of rod-shaped [RGaNH] 3n (R = H, CH 3) oligomers. Capping of oligomers with GaR and NH groups results in an almost periodic structure in which terminal groups affect only the very edges of the oligomer. The [RGaNH] 3n+1 rod-shaped oligomers are considered as an intermediate between finite clusters and [RGaNH] 3∞ polymer. Electronic properties of the oligomers are extrapolated to the infinite limit and band structure of the polymer is extracted from oligomer calculations. The energy gap of the [RGaNH] 3n+1 is defined by states localized at the different ends of the oligomer. The value of the gap is converging fast with increase of n, and it is about 93% of the value of the band gap of the polymer at the infinite limit. In contrast, termination of the [RGaNH] 3n rod-shaped oligomer by saturation of dangling bonds with H or CH 3 groups destroys the periodic pattern and increases the number of ends localized sates. This way of termination is characterized by systematic change in structural parameters of the oligomer and near exponential reduction of the energy gap with the oligomer length. For the rod-shaped oligomer of 10 nm of length the gap is only 27% of the [RGaNH] 3∞ polymer band gap and the value is not yet converged.
Theoretical Chemistry Accounts, Sep 7, 2014
ABSTRACT Structural and electronic properties of the rod-like oligomers formed by stacking of thr... more ABSTRACT Structural and electronic properties of the rod-like oligomers formed by stacking of three [RMNH]3 rings and have been theoretically investigated using DFT/TDDFT methods. Two types of oligomers have been considered: closed ones (terminated by RM and NH units) and open ones (terminated by three methyl groups and three hydrogen atoms). It is shown that terminal groups have significant influence on the electronic properties of oligomers due to the highly edge-localized nature of band gap states and huge difference in dipole moments. Ground state DFT calculations reveal that compared to closed oligomers, a profound reduction of energy gaps (by 1.6, 1.3 and 0.8 eV for M = Al, Ga, and In, respectively) is observed for open oligomers. Substitution of Ga atoms by Al results in moderate increase of energy gaps (up to 0.5 eV). Effect of substitution Ga atoms by In depends on the position of the substituted atoms. Excited states follow the same tendencies observed for the energy gaps.
![Research paper thumbnail of Why Do B–P and Al–P Polymers Differ? Structures, Stability, and Electronic Properties of Chain and Ring [H<sub>2</sub>PEH<sub>2</sub>]<sub><i>n</i></sub>Oligomers (E=B, Al;<i>n</i>=1<b>–</b>15)](https://attachments.academia-assets.com/108633338/thumbnails/1.jpg)
](Chemistry: A European Journal, Oct 24, 2018
Chain and ring [H2PEH2]n oligomers (E = B, Al; n = 2-15) have been computationally studied at the... more Chain and ring [H2PEH2]n oligomers (E = B, Al; n = 2-15) have been computationally studied at the B3LYP/def2-TZVP level of theory. A strong tendency to cyclization is found for the chain Al-P oligomers with n > 7, while analogous long B-P oligomers can exist as chain structures. Subsequent oligomerization enthalpies approach each other very closely for the ring and chain oligomers with the increase of n. However, these oligomers have very different electronic properties with band gaps below 0.2 eV for the chain [H2PBH2]15 and more than 5 eV for the ring isomer [H2PEH2]15. The MOs in the ring oligomers are highly delocalized, while, for the chain isomers, HOMO and LUMO are localized at the different ends of the oligomeric chain.
Journal of Physical Chemistry A, Apr 16, 2021
Electronic structures and thermodynamic characteristics of chain inorganic group 13-15 oligomers ... more Electronic structures and thermodynamic characteristics of chain inorganic group 13-15 oligomers [H2MEH2]n (M = B, Al, Ga, E = P, As; n = 4-15) are presented. Donor-acceptor interaction with both Lewis acids and Lewis bases effectively stabilizes chain isomers with respect to spontaneous cyclization and significantly changes their electronic structure.
Zeitschrift für anorganische und allgemeine Chemie, Feb 2, 2021
Solid state structures of five new molecular complexes of SbI3 with Py have been determined by si... more Solid state structures of five new molecular complexes of SbI3 with Py have been determined by single crystal X-ray structural analysis. In all complexes, all antimony atoms adopt a pseudooctahedral coordination geometry, which is completed by additional Sb•••I contacts shorter than sum of van der Waals radii, with I-Sb•••I angles close to 180º. Analysis of the electrostatic potentials, the orbital interactions and topological analysis indicate that these contacts are due to the presence of Sb•••I pnictogen bonds. The first example of three pnictogen bonds of SbI3 is reported.
Journal of Physical Chemistry B, Dec 13, 2013
Polyhedron, 2019
Molecular structures of two new SbCl 3-Py complexes, (SbCl 3) 4 Py 4 and (SbCl 3) 3 Py 5 , in the... more Molecular structures of two new SbCl 3-Py complexes, (SbCl 3) 4 Py 4 and (SbCl 3) 3 Py 5 , in the solid state have been determined by single crystal X-ray diffraction. In both complexes all Sb atoms adopt a pseudo-octahedral coordination geometry which is completed by additional Sb•••Cl contacts shorter than sum of van der Waals radii, with Cl-Sb•••Cl angles close to 180º. These contacts indicate the presence of Sb•••Cl pnictogen bonding. To reveal its nature, the DFT calculations were performed followed by the analyses of the electrostatic potentials, the orbital interactions and topological analysis.
Chemistry: A European Journal, Oct 28, 2020
Supporting information (SI) for this article is given via a link at the end of the document.
Journal of Chemical Theory and Computation, Oct 28, 2011
The performance in describing hydration free energies of a broad class of neutral, cationic, and ... more The performance in describing hydration free energies of a broad class of neutral, cationic, and anionic solutes is tested for the recently proposed FESR (Field-Extremum Short-Range) implicit solvation model for interactions between the solute and nearby water molecules, as taken in conjunction with the previously developed SS(V)PE (Surface and Simulation of Volume Polarization for Electrostatics) dielectric continuum model for long-range interactions with bulk water. The empirical FESR model mainly describes soluteÀwater hydrogen bonding interactions by correlating them with the maximum and minimum values of the electric field produced by the solute at the surface of the cavity that excludes solvent. A preliminary report showed that, with only four adjustable parameters, the FESR model, in conjunction with SS(V)PE, can produce hydration energies comparable to the best analogous efforts in the literature that utilized many more parameters. Here, the performance of the FESR model is more fully documented in several respects. The dependence on the underlying quantum mechanical method used to treat the internal electronic structure of the solute is tested by comparing uncorrelated HartreeÀFock to correlated density functional calculations and by comparing a modest sized to a large basis set. The influence of cavity size is studied in connection with an isodensity contour construction of the cavity. The sensitivity of the results to the parameters in the FESR model is considered, and it is found that the dependence on the electric field strength is quite nonlinear, with an optimum exponent consistently in the range of 3 to 4. Overall, it is concluded that the FESR model shows considerable utility for improving the accuracy of implicit models of aqueous solvation.
Physical Chemistry Chemical Physics, 2016
A DFT study of thermal decomposition mechanisms of [M(NH 2 BH 3) 2 ] 4 clusters with M = Mg, Ca, ... more A DFT study of thermal decomposition mechanisms of [M(NH 2 BH 3) 2 ] 4 clusters with M = Mg, Ca, and Sr is presented. Multi-step reaction pathways leading to elimination of the first H 2 molecule are explored at the M06/TZVP level of theory. For all studied M, the clusters adopt similar structures and exhibit similar transformations along the reaction pathways. Their activation energies decrease in the order Mg o Ca r Sr. Four metal atoms in the cluster form a rigid planar construction that is found to be nearly unchanged during all transformations. Cleavage of the B-H bond in the environment of alkaline-earth metal atoms leads to the ''capture'' of the released H atom by neighboring metal atoms with the formation of a M 3 H moiety. While the activation energies for the cleavage of H dÀ can be as low as 14.3, 22.6 and 23.3 kcal mol À1 for M = Mg, Ca and Sr, respectively, barriers for the subsequent cleavage of H d+ via destruction of the M 3 H moiety are about twice larger.
International Journal of Quantum Chemistry, May 1, 2009
Photophysical properties of polyethylene structures embedding aromatic fragments (benzene, anthra... more Photophysical properties of polyethylene structures embedding aromatic fragments (benzene, anthracene, 4-dicyanomethylene-4H-pyran, tryptophan, and estradiol) responsible for existence lowest electronically excited states were studied by new technique involving the elongation method applied to quantum-chemical calculations. Absorption spectra and some photophysical properties were obtained. The comparison between the elongation and the conventional calculations was made, and it is shown that the elongation method is a powerful tool to determine the excited states as well as optical properties for large systems.
Journal of Physical Chemistry A, Feb 3, 2009
The statistical quantum chemical/molecular dynamical method is developed and employed to reproduc... more The statistical quantum chemical/molecular dynamical method is developed and employed to reproduce optical spectra. This technique includes quantum-mechanical calculations on energy states and photophysical properties of molecular conformers obtained during molecular dynamical simulation. Polycyclic organic molecule estradiol surrounded by solvent particles and protein structure including tryptophan fragment under thermodynamical conditions are considered. A wide absorption spectrum over several excited electronic states of estradiol is constructed. First longwave absorption band of tryptophan-cage mini protein is built involving the elongation method. These statistical spectra reflect the main features of the corresponding experimental ones.
Russian Journal of General Chemistry, Apr 1, 2023
Chemical Physics Letters, Jul 1, 2011
A novel model of short-range contributions to hydration free energies is introduced for use with ... more A novel model of short-range contributions to hydration free energies is introduced for use with dielectric continuum treatment of long-range bulk electrostatics. The empirical model invokes extrema of the solute normal electric field at the cavity surface that nominally separates solute from solvent. It involves only a small handful of adjustable parameters, which are fitted to experimental data on a large collection of neutral and ionic solutes. The results show mean unsigned errors from experiment of only 0.9kcal/mol for neutrals and 2.4kcal/mol for ions, which are comparable to the best analogous previous efforts that utilize many more parameters.
Physical Chemistry Chemical Physics, 2016
The effect of electron-donating and electron-withdrawing terminal groups on the electronic struct... more The effect of electron-donating and electron-withdrawing terminal groups on the electronic structure of the rod-shaped X 3 [HGaNH] n Y 3 or needle-shaped XGa[HGaNH] n NY oligomers (X, Y = H, CH 3 , F, CF 3 ; n = 9, 30 and 114) was computationally studied at the B3LYP/SVP level of density functional theory. While the needle-shaped oligomers exhibit moderate variability in the electronic structure upon changing the terminal substituents X and Y, the energy gap of long rod-shaped oligomers varies within 2 eV. For oligomers with n = 114, F 3 [HGaNH] n (CH 3) 3 exhibits the largest HOMO-LUMO gap of 2.91 eV, while (CH 3) 3 [HGaNH] n F 3 has the smallest gap of 0.94 eV.
Journal of Physical Chemistry A, Jul 5, 2013
Implicit solvation models provide a very efficient means to estimate solvation energies. For exam... more Implicit solvation models provide a very efficient means to estimate solvation energies. For example, dielectric continuum models are commonly used to obtain the long-range electrostatic interactions. These may be parametrized to also include in some average manner short-range interactions such as dispersion and exchange, but it is preferable to instead develop additional implicit models specifically designed for the shortrange interactions. This work proposes new models for dispersion and exchange interactions between solute and solvent by adapting approaches previously developed for treatment of gas-phase intermolecular forces. The new models are formulated in terms of the charge densities of the solutes and use only three adjustable parameters. To illustrate the performance of the models, electronic structure calculations are reported for a large number of solutes in two nonpolar solvents where short-range interactions dominate and different balances pertain between attractive dispersion and repulsive exchange contributions. After empirical optimization of the requisite parameters, it is found that the errors compared to experimental solvation free energies are only about 0.4 kcal/mol on average, which is better than previous approaches in the literature that invoke many more parameters.
Nucleation and Atmospheric Aerosols, 2019
Using the methods of scanning electron microscopy (Scanning Electron Microscope-SEM) and X-ray ph... more Using the methods of scanning electron microscopy (Scanning Electron Microscope-SEM) and X-ray photoelectron spectroscopy (XPS), changes in the atomic structure and chemical state of multi-walled carbon nanotubes (MWCNTs) due to the action of ion beams of argon and helium with different irradiation parameters were investigated. Based on the experimental XPS and XANES (X-ray absorption near edge structure) data, as well as theoretical data, changes in the density of electronic states near the Fermi level in MWCNTs after ion-beam action were analyzed. It is shown that the use of beams of argon and helium ions can be used for directional functionalization of MWCNTs and applications in the chemical and petrochemical industries.
Springer eBooks, 2020
Synthetic approaches, structures, and reactivity of group 13–15 needle-shaped oligomers have been... more Synthetic approaches, structures, and reactivity of group 13–15 needle-shaped oligomers have been reviewed. Computational studies reveal that needle-shaped oligomers are more stable than fullerene-like isomers for all 13–15 pairs. Formation of such oligomers in the gas phase is energetically favorable and feasible from the thermodynamic point of view. However, many competitive reaction pathways are kinetically possible which leads to cascade of reactions and different reaction products. A systematic study of the various effects of structural variations on the electronic properties of Ga-N-based nanorods has been performed. On the basis of DFT computations, we demonstrate that terminal groups have a crucial impact on the electronic properties of the rod-shaped [RGaNH]3n (R=H, CH3) oligomers. Oligomers capped with GaR and NH groups adopt almost periodic structure in which terminal groups affect only the very edges of the oligomer. The band gap energy of the [HGaNH]3n+1 is defined by states localized at the different ends of the oligomer. The value of the band gap is converging fast with increase of n, and for n = 38 it is about 93% of the value of the band gap of the [HGaNH]3∞ polymer. In contrast, termination of the [HGaNH]3n rod-shaped oligomer by saturation of dangling bonds with H or CH3 groups destroys the periodic pattern and increases the number of states, localized at the ends of the oligomer. This way of termination is characterized by systematic change in structural parameters of the oligomer and near exponential decrease of the band gap energy with the oligomer length. The band gap energy for the rod-shaped oligomer of 10 nm of length (n = 38) amounts to only 27% of the value for the band gap of the [HGaNH]3∞ polymer. Substitution of Ga atoms by Al and In has also been considered. Absorption spectra undergo a red shift if Ga atoms are replaced by In atoms and a small blue shift if Ga atoms are replaced by Al atoms. The effect of electron-donating and electron-withdrawing terminal groups (H, CH3, F, CF3) on a dipole moment and energy gap values is found to be significant. The band gap energy of long tube-shaped Ga-N-based oligomers can be tuned within 2 eV by changing the substituents at the ends of the oligomer. A combined effect of all considered factors, substituent groups variations, rod’s elongation, and the way of ends’ termination, can help to vary energy gap of the [HGaNH]3n rod-shaped oligomer within the range 1–7 eV. Potential applications and further directions are also discussed.
Nucleation and Atmospheric Aerosols, 2007
ABSTRACT A method to build band structure of polymers from oligomer calculations has been develop... more ABSTRACT A method to build band structure of polymers from oligomer calculations has been developed. The correspondence between calculated energies of finite molecular chain and wave vector is obtained by projecting molecular orbitals (Mos) on the model Bloch functions. On the example of polydiacetylene, the reliability of the method for different computational methods (Hartree-Fock (HF), Density Functional Theory (DFT) with different basis sets) is shown.
Journal of Computational Chemistry, Jul 5, 2021
Energetic effects of solvation of SbF5, SbCl5, and 21 group 13 Lewis acids (LA) and their molecul... more Energetic effects of solvation of SbF5, SbCl5, and 21 group 13 Lewis acids (LA) and their molecular complexes with acetonitrile and pyridine are evaluated using SMD approach. Compared to the gas phase, solvation increases the stability of boron‐ and aluminum‐containing complexes but decreases the stability of gallium and indium‐containing homologs due to larger solation energies of free LA. New Lewis acidity scales, based on the Gibbs energy of dissociation of the molecular complexes LA·pyridine and LA·acetonitrile in the gas phase, in benzene and acetonitrile solutions, are proposed.
Journal of Physical Chemistry C, Jul 13, 2015
On the basis of DFT calculations, we demonstrate that terminal effects have a crucial impact on e... more On the basis of DFT calculations, we demonstrate that terminal effects have a crucial impact on electronic properties of rod-shaped [RGaNH] 3n (R = H, CH 3) oligomers. Capping of oligomers with GaR and NH groups results in an almost periodic structure in which terminal groups affect only the very edges of the oligomer. The [RGaNH] 3n+1 rod-shaped oligomers are considered as an intermediate between finite clusters and [RGaNH] 3∞ polymer. Electronic properties of the oligomers are extrapolated to the infinite limit and band structure of the polymer is extracted from oligomer calculations. The energy gap of the [RGaNH] 3n+1 is defined by states localized at the different ends of the oligomer. The value of the gap is converging fast with increase of n, and it is about 93% of the value of the band gap of the polymer at the infinite limit. In contrast, termination of the [RGaNH] 3n rod-shaped oligomer by saturation of dangling bonds with H or CH 3 groups destroys the periodic pattern and increases the number of ends localized sates. This way of termination is characterized by systematic change in structural parameters of the oligomer and near exponential reduction of the energy gap with the oligomer length. For the rod-shaped oligomer of 10 nm of length the gap is only 27% of the [RGaNH] 3∞ polymer band gap and the value is not yet converged.
Theoretical Chemistry Accounts, Sep 7, 2014
ABSTRACT Structural and electronic properties of the rod-like oligomers formed by stacking of thr... more ABSTRACT Structural and electronic properties of the rod-like oligomers formed by stacking of three [RMNH]3 rings and have been theoretically investigated using DFT/TDDFT methods. Two types of oligomers have been considered: closed ones (terminated by RM and NH units) and open ones (terminated by three methyl groups and three hydrogen atoms). It is shown that terminal groups have significant influence on the electronic properties of oligomers due to the highly edge-localized nature of band gap states and huge difference in dipole moments. Ground state DFT calculations reveal that compared to closed oligomers, a profound reduction of energy gaps (by 1.6, 1.3 and 0.8 eV for M = Al, Ga, and In, respectively) is observed for open oligomers. Substitution of Ga atoms by Al results in moderate increase of energy gaps (up to 0.5 eV). Effect of substitution Ga atoms by In depends on the position of the substituted atoms. Excited states follow the same tendencies observed for the energy gaps.
Chemistry: A European Journal, Oct 24, 2018
Chain and ring [H2PEH2]n oligomers (E = B, Al; n = 2-15) have been computationally studied at the... more Chain and ring [H2PEH2]n oligomers (E = B, Al; n = 2-15) have been computationally studied at the B3LYP/def2-TZVP level of theory. A strong tendency to cyclization is found for the chain Al-P oligomers with n > 7, while analogous long B-P oligomers can exist as chain structures. Subsequent oligomerization enthalpies approach each other very closely for the ring and chain oligomers with the increase of n. However, these oligomers have very different electronic properties with band gaps below 0.2 eV for the chain [H2PBH2]15 and more than 5 eV for the ring isomer [H2PEH2]15. The MOs in the ring oligomers are highly delocalized, while, for the chain isomers, HOMO and LUMO are localized at the different ends of the oligomeric chain.