Artëm E Masunov | University of Central Florida (original) (raw)
Papers by Artëm E Masunov
Combustion and Flame, 2020
Dimethyl methyl phosphonate (DMMP) is an organo-phosphorous compound (OPC) used as a fire suppres... more Dimethyl methyl phosphonate (DMMP) is an organo-phosphorous compound (OPC) used as a fire suppressant and a simulant for sarin, a chemical warfare agent. There exists a critical need to gather combustion data at high heating rate and high temperatures conditions, similar to what exists during destruction process of chemical weapons. In the present work, DMMP pyrolysis and oxidation were carried out behind reflected shock waves at temperatures of 130 0-170 0 K and pressures of 1.5-1.8 atm. Lean, stoichiometric, and rich DMMP mixtures (= 0.23, 0.5, 1, 2) were investigated for oxidation experiments. Laser absorption spectroscopy utilizing a quantum cascade laser near 4.9 μm was used to measure intermediate CO concentration formed during the pyrolysis and oxidation processes. To the best of our knowledge, we present the first intermediate concentration data at the reported conditions for DMMP. A tentative kinetic model, based on the AramcoMech2.0 mechanism with Lawrence Livermore National Lab (LLNL)'s OPC incineration chemistry, was utilized in Chemkin-Pro to predict CO yield during the processes. The model provided fair prediction of CO yield during DMMP pyrolysis, however, overpredicted the CO yield for oxidation. Sensitivity and rate of production analyses were carried out to understand important reactions leading to CO formation.
Vestnik Moskovskogo universiteta. Seriâ 2, Himiâ/Vestnik Moskovskogo universiteta. Seriâ Himiâ, Jul 2, 2024
ChemInform, Aug 19, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Combustion and Flame, Sep 1, 2023
A combined experimental and chemical kinetic modeling study of the high-temperature ignition and ... more A combined experimental and chemical kinetic modeling study of the high-temperature ignition and pyrolysis of 1,3-dimethylcyclohexane (13DMCH) is presented. Ignition delay times are measured behind reflected shock waves over a temperature range of 1049−1544 K and pressures of 3.0−12 atm. Pyrolysis is investigated at average pressures of 4.0 atm at temperatures of 1238, 1302, and 1406 K. By means of mid-infrared direct laser absorption at 3.39 μm, fuel concentration time histories are measured under ignition and pyrolytic conditions. A detailed chemical kinetic model for 13DMCH combustion is developed. Ignition measurements show that the ignition delay times of 13DMCH are longer than those of its isomer, ethylcyclohexane. The proposed chemical kinetic model predicts reasonably well the effects of equivalence ratio and pressure, with overall good agreement between predicted and measured ignition delay times, except at low dilution levels and high pressures. Simulated fuel concentration profiles agree reasonably well with the measured profiles, and both highlight the influence of pyrolysis on the overall ignition kinetics at high temperatures. Sensitivity and reaction pathway analyses provide further insight into the kinetic processes controlling ignition and pyrolysis. The work contributes toward improved understanding and modeling of the oxidation and pyrolysis kinetics of cycloalkanes.
Energy & Fuels, Nov 3, 2016
Journal of Chemical Physics, Jun 7, 2009
The photophysical properties of a symmetric squaryllium dye, namely, 2,4-bis͓4-͑N , N-dibutyl-ami... more The photophysical properties of a symmetric squaryllium dye, namely, 2,4-bis͓4-͑N , N-dibutyl-amino͒-2-hydroxyphenyl͔ squaraine ͑SQ͒, in its monomer form in acetone solution, have been thoroughly studied by means of one-photon absorption ͑1PA͒ and two-photon absorption ͑2PA͒, excitation anisotropy, fluorescence emission, fluorescence quantum yield, and excited state absorption. The results show that there is a strong one-photon allowed absorption band in the near IR region associated with intramolecular charge transfer. Higher one-photon allowed and forbidden singlet excited states were also revealed by absorption and excitation anisotropy. A relatively high fluorescence quantum yield ͑0.44͒ was measured for this dye. The nonlinear optical characterization of SQ in solution confirms the ability of squaraine dyes to be used as good two-photon absorbers. Additionally, it was found that this dye presents both saturable and reverse saturable absorption effects. Density functional theory calculations of the 1PA and 2PA electronic spectra of SQ were carried out to support the experimental data. A detailed analysis of the symmetry and energy of the orbitals involved in the lowest five electronic transitions is presented and discussed in relation to the behavior observed experimentally.
Journal of Cluster Science, Jun 16, 2022
Journal of Physical Chemistry A, Jul 23, 2021
About 9000 structures of magnesium clusters Mgn (n = 2-13) generated via different methods were o... more About 9000 structures of magnesium clusters Mgn (n = 2-13) generated via different methods were optimized at the DFT levels in order to estimate the number of all possible stable structures that can exist for the given cluster size (∼820,000 PES points were explored in total). It was found that the number of possible cluster isomers N quickly grows with a number of atoms n; however, it is significantly lower than the number of possible nonisomorphic graph structures, which can be drawn for the given n. At the DFT potential energy surface, we found only 543 local minima corresponding to the isomers of Mg2-Mg13. The number of isomers obtained in the DFT optimizations grows with n approximately as n4, whereas the N values extrapolated to the infinite generation process grow as n8. The cluster geometries obtained from the global DFT optimization were then used to adjust two empirical potentials of Gupta type (GP) and modified Sutton-Chen type (SCG3) describing the interactions between the magnesium atoms. Using these potentials, the extensive sets of structures Mg2-Mg55 (up to 30,000 clusters for each n) were optimized to obtain the dependence of the cluster isomer count on n in the continuous range of n = 2-30 and for selected n up to n = 55. It was found that the SCG3 potential, which is closer to the DFT results, gives a number of possible isomers growing as approximately n8.9, whereas GP potential results in the n4.3 dependence.
RSC Advances, 2023
The isotropic electrostatic polarizability (IEP) of sub-nanosized magnesium clusters Mg 2-Mg 32 w... more The isotropic electrostatic polarizability (IEP) of sub-nanosized magnesium clusters Mg 2-Mg 32 was studied in an extensive set comprising 1237 structurally unique isomers. These isomers were found in the course of the global search for the potential energy surface minima of the magnesium clusters at the BP86/6-31G(d) level. The calculation of the polarizability at the same DFT level reveals an unexpected property of the IEP: the linear correlation between the polarizability of the most favorable isomers (and only them) and the cluster nuclearity n. Moreover, for each n, the most stable cluster isomer demonstrates nearly minimal IEP value among all found isomers of a given nuclearity. Surprisingly, these observed features are independent of the cluster structures which are quite different. We hypothesize that the energetic favorability of a cluster structure is related to their low polarizability. Apparently, the atoms forming the cluster tend to arrange themselves in such a way as to provide the most compact distribution of the cluster electron density. A possible explanation of the observed trends, their significance for cluster structure prediction, and the practical applications are discussed.
Journal of Physical Chemistry A, Jul 7, 2021
The 4-hydroxypyrrolidine-2-carboxanilide podand salt demonstrates catalytic activity in asymmetri... more The 4-hydroxypyrrolidine-2-carboxanilide podand salt demonstrates catalytic activity in asymmetric Biginelli reaction. The systematic search for prevalent conformational state of the cation was carried out by computer simulations in combination with one- and two-dimensional NMR experiments. For that purpose, we proposed a novel algorithm for the generation and selection of conformers based on molecular dynamics and clustering in the space of principal components. The search had found an important trend of the podand to form a pseudocyclic structure with a horseshoe-shaped conformation of the oligooxyethylene fragment. This conformation is stabilized by different types of intramolecular hydrogen bonds between the acidic and basic centers of the two 4-hydroxypyrrolidine-2-carboxanilide residuals (branches). The proposed approach had made it possible to identify the major structural factors, providing a correlation between the calculated and experimental chemical shifts of hydrogen atoms in the 1H NMR spectra of the protonated podand.
Journal of Physical Chemistry A, Mar 29, 2019
Tri-ethyl phosphate (TEP) is an organophosphorous compound (OPC) used as a simulant for highly to... more Tri-ethyl phosphate (TEP) is an organophosphorous compound (OPC) used as a simulant for highly toxic nerve agents such as Sarin GB. High temperature decomposition pathway during TEP pyrolysis has been proposed previously and takes place via seven concerted elimination reactions. Computational study to investigate the kinetics of these seven reactions is carried out at CBS-QB3 level of theory. The transition state optimization is done at B3LYP/6-311G(2d,d,p) theory level and CanTherm is used to derive the Arrhenius coefficients. The pre-exponential factors of the rate constant of these reactions are found to be up to 50 times lower than the estimated values from the literature. In addition, kinetics of reaction of trioxidophosphorus radical (PO3) with H2 (H2+PO3=HOPO2+H); which is one of the important reactions in predicting CO formation during TEP decomposition, is also investigated computationally at the same theory level. The new kinetic parameters derived from the computational study is used with TEP kinetic model proposed recently by our group. In addition, an alternative decomposition pathway for TEP decomposition
Materials Advances
Push–pull chromophores exhibit useful electro-optic (EO) properties that have the potential to si... more Push–pull chromophores exhibit useful electro-optic (EO) properties that have the potential to significantly improve non-linear EO applications ranging from telecommunications to quantum informatics.
Crystal Growth & Design
Crystal Growth & Design, 2020
We report on development of the novel methodology for computational predictions of the mechanical... more We report on development of the novel methodology for computational predictions of the mechanical properties of single crystals. This methodology is based on constrained optimization using dispersion-corrected density functional theory level, and can be dubbed Virtual Tensile Test. The approach was validated on the example of 4-bromophenyl 4-bromobenzoate, an organic compound known to form three polymorphs with different mechanical characteristics. Each one of these polymorphic crystal structures was stretched stepwise along each crystallographic axis, while relaxing remaining lattice parameters and atomic coordinates. The geometrical properties of halogen bonds and the other non-covalent interactions were monitored at each step to understand the nature of mechanical response. The unit cell volumes and lattice energies were plotted as functions of the stretching parameter, and these curves were analyzed in terms of mechanical properties of the brittle, plastic, and elastic polymorphs.
The Journal of Physical Chemistry A, 2018
Pyrolysis and oxidation of triethyl phosphate (TEP) were performed in the reflected shock region ... more Pyrolysis and oxidation of triethyl phosphate (TEP) were performed in the reflected shock region at temperatures of 1462-1673 K and 1213-1508 K, respectively, and at pressures near 1.3 atm. CO concentration time histories during the experiments were measured using laser absorption spectroscopy at 4580.4 nm. Experimental CO yields were compared with model predictions using the detailed organophosphorus compounds (OPC) incineration mechanism from the Lawrence Livermore National Lab (LLNL). The mechanism significantly underpredicts CO yield in TEP pyrolysis. During TEP oxidation, predicted rate of CO formation was significantly slower than the experimental results. Therefore, a new improved kinetic model for TEP combustion was developed, which was built upon the AramcoMech2.0 mechanism for C0-C2 chemistry and the existing LLNL submechanism for phosphorus chemistry. Thermochemical data of 40 phosphorus (P)-containing species were reevaluated, either using recently published group values for P-containing species or by quantum chemical calculations (CBS-QB3). The new improved model is in better agreement with the experimental CO time histories within the temperature and pressure conditions tested in this study. Sensitivity analysis was used to identify important reactions affecting CO formation, and future experimental/theoretical studies on kinetic parameters of these reactions were suggested to further improve the model. To the best of our knowledge, this is the first study of TEP kinetics in a shock tube under these conditions and the first time-resolved laser-based species time history data during its pyrolysis and oxidation.
Journal of Dispersion Science and Technology, 2018
The molecular dynamics (MD) simulation method was used to simulate the aggregation of four types ... more The molecular dynamics (MD) simulation method was used to simulate the aggregation of four types of surfactants at the oil/water interface. The effect of different cations such as Na þ , Mg 2þ and Ca 2þ was compared. The results show that the interaction between different types and concentrations of cationic and head group of surfactants causes the surfactant adsorption layer to bend and changes the aggregation morphology of the micelles. The radial distribution function (RDF) of the surfactant head groups with water molecules and cations is calculated. The calculated results show that it exists a chemical hydration layer and a physical hydration layer between the surfactant head groups and the water molecules. Cation has different degrees of impact, thus changes the original hydration structure. Nonionic and zwitterion surfactants have good salt resistance. Potential of Mean Force (PMF) was used to analyze the energy change when the cation interacted with the polar head. The nonionic and zwitterion surfactants are determined to have a good oil displacement effect even under the conditions of high calcium-magnesium mineralization. The present results could help in choosing surfactants used in oil/water with inorganic salts.
The Journal of Physical Chemistry A, 2017
The supercritical carbon dioxide diluent is used to control the temperature and to increase the e... more The supercritical carbon dioxide diluent is used to control the temperature and to increase the efficiency in oxycombustion fossil fuel energy technology. It may affect the rates of combustion by altering mechanisms of chemical reactions, compared to the ones at low CO 2 concentrations. Here, we investigate potential energy surfaces of the four elementary reactions in the CH 3 + O 2 reactive system in the presence of one CO 2 molecule. In the case of reaction CH 3 + O 2 → CH 2 O + OH (R1 channel), van der Waals (vdW) complex formation stabilizes the transition state and reduces the activation barrier by ∼2.2 kcal/mol. Alternatively, covalently bonded CO 2 may form a six-membered ring transition state and reduce the activation barrier by ∼0.6 kcal/mol. In case of reaction CH 3 + O 2 → CH 3 O + O (R2 channel), covalent participation of CO 2 lowers the barrier for the rate limiting step by 3.9 kcal/mol. This is expected to accelerate the R2 process, important for the branching step of the radical chain reaction mechanism. For the reaction CH 3 + O 2 → CHO + H 2 O (R3 channel) with covalent participation of CO 2 , the activation barrier is lowered by 0.5 kcal/mol. The reaction CH 2 O + OH → CHO + H 2 O (R4 channel) involves hydrogen abstraction from formaldehyde by OH radical. Its barrier is reduced from 7.1 to 0.8 kcal/mol by formation of vdW complex with spectator CO 2. These new findings are expected to improve the kinetic reaction mechanism describing combustion processes in supercritical CO 2 medium.
Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration; Organic Rankine Cycle Power Systems, 2016
Journal of Luminescence, 2017
Abstract The steady-state and time-resolved linear spectral properties, two-photon absorption spe... more Abstract The steady-state and time-resolved linear spectral properties, two-photon absorption spectra and fast relaxation processes in the excited states of styryl base-type derivatives were investigated. The nature of linear absorption, fluorescence and excitation anisotropy spectra were analyzed in solvents of different polarity at room temperature and specific dependence of the solvatochromic behavior on the donor-acceptor strength of the terminal substituents was shown. Two-photon absorption (2PA) efficiency of styryl dye bases was determined in a broad spectral range using two-photon induced fluorescence technique, and cross-sections maxima of ~ 100 GM were found. The excited state absorption (ESA) and fast relaxation processes in the molecular structures were investigated by transient absorption femtosecond pump-probe methodology. The role of twisted intramolecular charge transfer (TICT) effect in the excited state of styryl dye base with dimethylamino substituent was shown. The experimental spectroscopic data were also verified by quantum chemical calculations at the Time Dependent Density Functional Theory level, combined with a polarizable continuum model.
Combustion and Flame, 2020
Dimethyl methyl phosphonate (DMMP) is an organo-phosphorous compound (OPC) used as a fire suppres... more Dimethyl methyl phosphonate (DMMP) is an organo-phosphorous compound (OPC) used as a fire suppressant and a simulant for sarin, a chemical warfare agent. There exists a critical need to gather combustion data at high heating rate and high temperatures conditions, similar to what exists during destruction process of chemical weapons. In the present work, DMMP pyrolysis and oxidation were carried out behind reflected shock waves at temperatures of 130 0-170 0 K and pressures of 1.5-1.8 atm. Lean, stoichiometric, and rich DMMP mixtures (= 0.23, 0.5, 1, 2) were investigated for oxidation experiments. Laser absorption spectroscopy utilizing a quantum cascade laser near 4.9 μm was used to measure intermediate CO concentration formed during the pyrolysis and oxidation processes. To the best of our knowledge, we present the first intermediate concentration data at the reported conditions for DMMP. A tentative kinetic model, based on the AramcoMech2.0 mechanism with Lawrence Livermore National Lab (LLNL)'s OPC incineration chemistry, was utilized in Chemkin-Pro to predict CO yield during the processes. The model provided fair prediction of CO yield during DMMP pyrolysis, however, overpredicted the CO yield for oxidation. Sensitivity and rate of production analyses were carried out to understand important reactions leading to CO formation.
Vestnik Moskovskogo universiteta. Seriâ 2, Himiâ/Vestnik Moskovskogo universiteta. Seriâ Himiâ, Jul 2, 2024
ChemInform, Aug 19, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Combustion and Flame, Sep 1, 2023
A combined experimental and chemical kinetic modeling study of the high-temperature ignition and ... more A combined experimental and chemical kinetic modeling study of the high-temperature ignition and pyrolysis of 1,3-dimethylcyclohexane (13DMCH) is presented. Ignition delay times are measured behind reflected shock waves over a temperature range of 1049−1544 K and pressures of 3.0−12 atm. Pyrolysis is investigated at average pressures of 4.0 atm at temperatures of 1238, 1302, and 1406 K. By means of mid-infrared direct laser absorption at 3.39 μm, fuel concentration time histories are measured under ignition and pyrolytic conditions. A detailed chemical kinetic model for 13DMCH combustion is developed. Ignition measurements show that the ignition delay times of 13DMCH are longer than those of its isomer, ethylcyclohexane. The proposed chemical kinetic model predicts reasonably well the effects of equivalence ratio and pressure, with overall good agreement between predicted and measured ignition delay times, except at low dilution levels and high pressures. Simulated fuel concentration profiles agree reasonably well with the measured profiles, and both highlight the influence of pyrolysis on the overall ignition kinetics at high temperatures. Sensitivity and reaction pathway analyses provide further insight into the kinetic processes controlling ignition and pyrolysis. The work contributes toward improved understanding and modeling of the oxidation and pyrolysis kinetics of cycloalkanes.
Energy & Fuels, Nov 3, 2016
Journal of Chemical Physics, Jun 7, 2009
The photophysical properties of a symmetric squaryllium dye, namely, 2,4-bis͓4-͑N , N-dibutyl-ami... more The photophysical properties of a symmetric squaryllium dye, namely, 2,4-bis͓4-͑N , N-dibutyl-amino͒-2-hydroxyphenyl͔ squaraine ͑SQ͒, in its monomer form in acetone solution, have been thoroughly studied by means of one-photon absorption ͑1PA͒ and two-photon absorption ͑2PA͒, excitation anisotropy, fluorescence emission, fluorescence quantum yield, and excited state absorption. The results show that there is a strong one-photon allowed absorption band in the near IR region associated with intramolecular charge transfer. Higher one-photon allowed and forbidden singlet excited states were also revealed by absorption and excitation anisotropy. A relatively high fluorescence quantum yield ͑0.44͒ was measured for this dye. The nonlinear optical characterization of SQ in solution confirms the ability of squaraine dyes to be used as good two-photon absorbers. Additionally, it was found that this dye presents both saturable and reverse saturable absorption effects. Density functional theory calculations of the 1PA and 2PA electronic spectra of SQ were carried out to support the experimental data. A detailed analysis of the symmetry and energy of the orbitals involved in the lowest five electronic transitions is presented and discussed in relation to the behavior observed experimentally.
Journal of Cluster Science, Jun 16, 2022
Journal of Physical Chemistry A, Jul 23, 2021
About 9000 structures of magnesium clusters Mgn (n = 2-13) generated via different methods were o... more About 9000 structures of magnesium clusters Mgn (n = 2-13) generated via different methods were optimized at the DFT levels in order to estimate the number of all possible stable structures that can exist for the given cluster size (∼820,000 PES points were explored in total). It was found that the number of possible cluster isomers N quickly grows with a number of atoms n; however, it is significantly lower than the number of possible nonisomorphic graph structures, which can be drawn for the given n. At the DFT potential energy surface, we found only 543 local minima corresponding to the isomers of Mg2-Mg13. The number of isomers obtained in the DFT optimizations grows with n approximately as n4, whereas the N values extrapolated to the infinite generation process grow as n8. The cluster geometries obtained from the global DFT optimization were then used to adjust two empirical potentials of Gupta type (GP) and modified Sutton-Chen type (SCG3) describing the interactions between the magnesium atoms. Using these potentials, the extensive sets of structures Mg2-Mg55 (up to 30,000 clusters for each n) were optimized to obtain the dependence of the cluster isomer count on n in the continuous range of n = 2-30 and for selected n up to n = 55. It was found that the SCG3 potential, which is closer to the DFT results, gives a number of possible isomers growing as approximately n8.9, whereas GP potential results in the n4.3 dependence.
RSC Advances, 2023
The isotropic electrostatic polarizability (IEP) of sub-nanosized magnesium clusters Mg 2-Mg 32 w... more The isotropic electrostatic polarizability (IEP) of sub-nanosized magnesium clusters Mg 2-Mg 32 was studied in an extensive set comprising 1237 structurally unique isomers. These isomers were found in the course of the global search for the potential energy surface minima of the magnesium clusters at the BP86/6-31G(d) level. The calculation of the polarizability at the same DFT level reveals an unexpected property of the IEP: the linear correlation between the polarizability of the most favorable isomers (and only them) and the cluster nuclearity n. Moreover, for each n, the most stable cluster isomer demonstrates nearly minimal IEP value among all found isomers of a given nuclearity. Surprisingly, these observed features are independent of the cluster structures which are quite different. We hypothesize that the energetic favorability of a cluster structure is related to their low polarizability. Apparently, the atoms forming the cluster tend to arrange themselves in such a way as to provide the most compact distribution of the cluster electron density. A possible explanation of the observed trends, their significance for cluster structure prediction, and the practical applications are discussed.
Journal of Physical Chemistry A, Jul 7, 2021
The 4-hydroxypyrrolidine-2-carboxanilide podand salt demonstrates catalytic activity in asymmetri... more The 4-hydroxypyrrolidine-2-carboxanilide podand salt demonstrates catalytic activity in asymmetric Biginelli reaction. The systematic search for prevalent conformational state of the cation was carried out by computer simulations in combination with one- and two-dimensional NMR experiments. For that purpose, we proposed a novel algorithm for the generation and selection of conformers based on molecular dynamics and clustering in the space of principal components. The search had found an important trend of the podand to form a pseudocyclic structure with a horseshoe-shaped conformation of the oligooxyethylene fragment. This conformation is stabilized by different types of intramolecular hydrogen bonds between the acidic and basic centers of the two 4-hydroxypyrrolidine-2-carboxanilide residuals (branches). The proposed approach had made it possible to identify the major structural factors, providing a correlation between the calculated and experimental chemical shifts of hydrogen atoms in the 1H NMR spectra of the protonated podand.
Journal of Physical Chemistry A, Mar 29, 2019
Tri-ethyl phosphate (TEP) is an organophosphorous compound (OPC) used as a simulant for highly to... more Tri-ethyl phosphate (TEP) is an organophosphorous compound (OPC) used as a simulant for highly toxic nerve agents such as Sarin GB. High temperature decomposition pathway during TEP pyrolysis has been proposed previously and takes place via seven concerted elimination reactions. Computational study to investigate the kinetics of these seven reactions is carried out at CBS-QB3 level of theory. The transition state optimization is done at B3LYP/6-311G(2d,d,p) theory level and CanTherm is used to derive the Arrhenius coefficients. The pre-exponential factors of the rate constant of these reactions are found to be up to 50 times lower than the estimated values from the literature. In addition, kinetics of reaction of trioxidophosphorus radical (PO3) with H2 (H2+PO3=HOPO2+H); which is one of the important reactions in predicting CO formation during TEP decomposition, is also investigated computationally at the same theory level. The new kinetic parameters derived from the computational study is used with TEP kinetic model proposed recently by our group. In addition, an alternative decomposition pathway for TEP decomposition
Materials Advances
Push–pull chromophores exhibit useful electro-optic (EO) properties that have the potential to si... more Push–pull chromophores exhibit useful electro-optic (EO) properties that have the potential to significantly improve non-linear EO applications ranging from telecommunications to quantum informatics.
Crystal Growth & Design
Crystal Growth & Design, 2020
We report on development of the novel methodology for computational predictions of the mechanical... more We report on development of the novel methodology for computational predictions of the mechanical properties of single crystals. This methodology is based on constrained optimization using dispersion-corrected density functional theory level, and can be dubbed Virtual Tensile Test. The approach was validated on the example of 4-bromophenyl 4-bromobenzoate, an organic compound known to form three polymorphs with different mechanical characteristics. Each one of these polymorphic crystal structures was stretched stepwise along each crystallographic axis, while relaxing remaining lattice parameters and atomic coordinates. The geometrical properties of halogen bonds and the other non-covalent interactions were monitored at each step to understand the nature of mechanical response. The unit cell volumes and lattice energies were plotted as functions of the stretching parameter, and these curves were analyzed in terms of mechanical properties of the brittle, plastic, and elastic polymorphs.
The Journal of Physical Chemistry A, 2018
Pyrolysis and oxidation of triethyl phosphate (TEP) were performed in the reflected shock region ... more Pyrolysis and oxidation of triethyl phosphate (TEP) were performed in the reflected shock region at temperatures of 1462-1673 K and 1213-1508 K, respectively, and at pressures near 1.3 atm. CO concentration time histories during the experiments were measured using laser absorption spectroscopy at 4580.4 nm. Experimental CO yields were compared with model predictions using the detailed organophosphorus compounds (OPC) incineration mechanism from the Lawrence Livermore National Lab (LLNL). The mechanism significantly underpredicts CO yield in TEP pyrolysis. During TEP oxidation, predicted rate of CO formation was significantly slower than the experimental results. Therefore, a new improved kinetic model for TEP combustion was developed, which was built upon the AramcoMech2.0 mechanism for C0-C2 chemistry and the existing LLNL submechanism for phosphorus chemistry. Thermochemical data of 40 phosphorus (P)-containing species were reevaluated, either using recently published group values for P-containing species or by quantum chemical calculations (CBS-QB3). The new improved model is in better agreement with the experimental CO time histories within the temperature and pressure conditions tested in this study. Sensitivity analysis was used to identify important reactions affecting CO formation, and future experimental/theoretical studies on kinetic parameters of these reactions were suggested to further improve the model. To the best of our knowledge, this is the first study of TEP kinetics in a shock tube under these conditions and the first time-resolved laser-based species time history data during its pyrolysis and oxidation.
Journal of Dispersion Science and Technology, 2018
The molecular dynamics (MD) simulation method was used to simulate the aggregation of four types ... more The molecular dynamics (MD) simulation method was used to simulate the aggregation of four types of surfactants at the oil/water interface. The effect of different cations such as Na þ , Mg 2þ and Ca 2þ was compared. The results show that the interaction between different types and concentrations of cationic and head group of surfactants causes the surfactant adsorption layer to bend and changes the aggregation morphology of the micelles. The radial distribution function (RDF) of the surfactant head groups with water molecules and cations is calculated. The calculated results show that it exists a chemical hydration layer and a physical hydration layer between the surfactant head groups and the water molecules. Cation has different degrees of impact, thus changes the original hydration structure. Nonionic and zwitterion surfactants have good salt resistance. Potential of Mean Force (PMF) was used to analyze the energy change when the cation interacted with the polar head. The nonionic and zwitterion surfactants are determined to have a good oil displacement effect even under the conditions of high calcium-magnesium mineralization. The present results could help in choosing surfactants used in oil/water with inorganic salts.
The Journal of Physical Chemistry A, 2017
The supercritical carbon dioxide diluent is used to control the temperature and to increase the e... more The supercritical carbon dioxide diluent is used to control the temperature and to increase the efficiency in oxycombustion fossil fuel energy technology. It may affect the rates of combustion by altering mechanisms of chemical reactions, compared to the ones at low CO 2 concentrations. Here, we investigate potential energy surfaces of the four elementary reactions in the CH 3 + O 2 reactive system in the presence of one CO 2 molecule. In the case of reaction CH 3 + O 2 → CH 2 O + OH (R1 channel), van der Waals (vdW) complex formation stabilizes the transition state and reduces the activation barrier by ∼2.2 kcal/mol. Alternatively, covalently bonded CO 2 may form a six-membered ring transition state and reduce the activation barrier by ∼0.6 kcal/mol. In case of reaction CH 3 + O 2 → CH 3 O + O (R2 channel), covalent participation of CO 2 lowers the barrier for the rate limiting step by 3.9 kcal/mol. This is expected to accelerate the R2 process, important for the branching step of the radical chain reaction mechanism. For the reaction CH 3 + O 2 → CHO + H 2 O (R3 channel) with covalent participation of CO 2 , the activation barrier is lowered by 0.5 kcal/mol. The reaction CH 2 O + OH → CHO + H 2 O (R4 channel) involves hydrogen abstraction from formaldehyde by OH radical. Its barrier is reduced from 7.1 to 0.8 kcal/mol by formation of vdW complex with spectator CO 2. These new findings are expected to improve the kinetic reaction mechanism describing combustion processes in supercritical CO 2 medium.
Volume 3: Coal, Biomass and Alternative Fuels; Cycle Innovations; Electric Power; Industrial and Cogeneration; Organic Rankine Cycle Power Systems, 2016
Journal of Luminescence, 2017
Abstract The steady-state and time-resolved linear spectral properties, two-photon absorption spe... more Abstract The steady-state and time-resolved linear spectral properties, two-photon absorption spectra and fast relaxation processes in the excited states of styryl base-type derivatives were investigated. The nature of linear absorption, fluorescence and excitation anisotropy spectra were analyzed in solvents of different polarity at room temperature and specific dependence of the solvatochromic behavior on the donor-acceptor strength of the terminal substituents was shown. Two-photon absorption (2PA) efficiency of styryl dye bases was determined in a broad spectral range using two-photon induced fluorescence technique, and cross-sections maxima of ~ 100 GM were found. The excited state absorption (ESA) and fast relaxation processes in the molecular structures were investigated by transient absorption femtosecond pump-probe methodology. The role of twisted intramolecular charge transfer (TICT) effect in the excited state of styryl dye base with dimethylamino substituent was shown. The experimental spectroscopic data were also verified by quantum chemical calculations at the Time Dependent Density Functional Theory level, combined with a polarizable continuum model.
Journal of the American Chemical Society, 2001
... s^ern2nclex, ^,X<, (pr2nci8co Xl>, 1952- 1ntroc1uction to peNurb2tion tneorv in qu2ntum... more ... s^ern2nclex, ^,X<, (pr2nci8co Xl>, 1952- 1ntroc1uction to peNurb2tion tneorv in qu2ntum mecnllnic8/pr2nci8co ^l. pernänclex, p, cm, lnclucle8 biblioßr2pnic2l ...
We found unexpected near infrared (NIR) photo response in CdSe nanocrystal superlattice film anne... more We found unexpected near infrared (NIR) photo response in CdSe nanocrystal superlattice film annealed above 400 C in air. The current voltage characteristic measured in a planer device geometry show a large increase in NIR current over dark current. The calculated external ...
iv Abstract MOLECULAR AND CRYSTAL ORBITAL STUDIES OF ORGANIC CRYSTAL FORMATION by Artem Masunov A... more iv Abstract MOLECULAR AND CRYSTAL ORBITAL STUDIES OF ORGANIC CRYSTAL FORMATION by Artem Masunov Adviser: Professor J. J. Dannenberg Ab initio molecular orbital and crystal orbital methods are applied to the study of the geometry of hydrogen-bonded organic crystals and to predict the relative stability of polymorphic modifications. Cluster calculations of para-benzoquinone, of urea and of thiourea at HF, DFT, and AM1 levels with pseudotranslational constraints allow for the analysis of the energies for each type of H-bonds and their dependence on the cluster size. Periodical calculations on infinite systems are in good agreement with the results of cluster calculations. The cooperative components of intermolecular interaction, which are neglected in the most empirical force-field models account for up to 30% of the total interactions in the systems considered. This non-additivity is shown to lead to experimentally observed differences in crystal packing between urea and thourea, and can be successfully reproduced at the practically justified approximations. One important application of MO calculations is to build simple yet accurate models for intermolecular interactions. Modifications of the basis set by optimizing the centroid positions of each basis function (floating basis set) combined with 2.