Density Of States Spectrum Research Articles

Application of PLA/GO/ZnO and PLA/GO/Cu2O as sensor

Polylactic acid modified with graphene oxide (PLA/GO) is proposed to interact with ZnO through 6 different schemes. Density functional theory at B3LYP/LANL2DZ level was utilized to calculate total dipole moment (TDM), HOMO/LUMO energy gap (ΔE) and to map the molecular electrostatic potential (MESP). Results indicated that PLA/GO interacted with ZnO through O-atom forming PLA/GO/OZn composite. This composite interacts with methane, hydrogen sulfide, humidity (H2O), carbon dioxide and ethanol. The same gases were supposed to interact further with PLA/GO/Cu2O. Adsorption energy for the interaction between each composite and the proposed gases were calculated. Both PLA/GO/OZn and PLA/GO/Cu2O composites interacted favorably with H2O. Adsorption energy for interaction of other gases with studied structures are generally low compared to H2O. PLA/GO/OZn have adsorption energy slightly higher than that of PLA/GO/Cu2O. PLA/GO/OZn has higher TDM values than those of PLA/GO/Cu2O, indicating a more polar material. Conversely, PLA/GO/Cu2O exhibited larger ΔE values than those of PLA/GO/OZn. TDM and energy gap results for both studied structures indicated good sensing capabilities. Further insights come from analyzing the calculated density of states (DOS) and partial density of states (PDOS). PLA/GO/Cu2O exhibited high peak for copper in its DOS and PDOS spectra compared to zinc and oxygen in case of PLA/GO/OZn. This means a higher density of available electronic states associated with Cu.

Comparative bioengineering and optoelectronic properties of metoprolol by DFT, molecular docking, and molecular dynamic approaches

The biophysical properties of metoprolol are investigated by the full potential-linearized augmented plane wave method and molecular docking and molecular dynamic approaches. The exchange–correlation potentials are calculated by the Perdew–Burke–Ernzerhof generalized gradient approximation as implemented in the WIEN2k package. The electronic results show the insulator nature of metoprolol with the indirect bandgap of 3.74 eV between HOMO and LUMO states. In the density of state spectra, the p state of O, C, and N elements confirm the stability of metoprolol. Metoprolol exhibits a metallic behavior in the z direction, while it has a dielectric behavior in the x and y directions. The static refractive indices are obtained 1.49, 1.53, and 1.63 in the x, y, and z directions, respectively. It was found that the maximum reflectivity occurs at the ultraviolet region in the z-direction. The calculated absorption spectra also confirm the other’s experimental results. The obtained results of molecular docking indicate the formation of hydrogen bonds between metoprolol and the beta-2 adrenergic receptors, and molecular dynamics showed a human beta-2 adrenoceptor either in its free state or in complex with a metoprolol molecule. The calculated binding energies of elements by molecular docking and the other biological properties of metoprolol by molecular dynamic are in close agreement with obtained Density Functional Theory (DFT) results for Pharmacia applications.

Properties of bismuth based Bi2A3 (A = S, Se, Te) chalcogenides for optoelectronic and thermoelectric applications

Structural, electronic, optical, mechanical, thermoelectric and dielectric properties of binary Bi2A3 (A = S, Se, Te) chalcogenide semiconductors are studied by first-principles approach. Bismuth sulfide (Bi2S3) is found to be structurally stable in orthorhombic structure while bismuth selenide (Bi2Se3) and bismuth telluride (Bi2Te3) are stable in trigonal structure. Calculated mechanical properties reveal that all three Bi2A3 (A = S, Se, Te) compounds fulfil the mechanical stability criteria. Band structure calculations reveal that the Bi2S3 exhibits direct optical band gap (Eg = 1. 58 eV) which lies in the near-infrared (NIR) region, while the calculated Eg of Bi2Se3 and Bi2Te3 are found to be 0.53 eV and 0.35 eV, respectively lying in the far-infrared region. For Bi2S3 and Bi2Se3 compounds, the calculated dielectric properties show strong anisotropic behavior, while negligible anisotropic dielectric behavior is observed for Bi2Te3. Calculated optical properties show that all three Bi2A3 compounds possess high absorption coefficient (> 104 cm−1). For all three Bi2A3 (A = S, Se, Te) compounds, the calculated optical conductivity show prominent peak corresponding to the occurrence of optical conduction at energies 3.36 eV, 2.65 eV and 2.02 eV respectively. Calculated optical results support the results deduced from band structures and density of states spectra. Optical properties and dielectric behavior suggest that the Bi2S3 compound has suitable band gap and has potential to use for photovoltaic applications while Bi2A3 (A = Se, Te) compounds could be used in infrared detectors and other optical devices. Calculated thermal properties reveal that the Bi2A3 (A = S, Se, Te) chalcogenides could be potential materials for thermoelectric applications.

Theoretical, structural, and electronic analyses of pyridin-based dyes for dye-sensitized solar cells applications.

The new series of donor-π-acceptor dyes have been designed using pyridine derivatives as a donor group and thienothiophene as a π-spacer group, which were linked via 10acceptor groups. The highest occupied molecular orbital energies range from - 6.177 to - 5.786eV, whereas the lowest unoccupied molecular orbital energies range from - 2.181 to - 3.664eV. A6 dye has smaller energy gap, lower hardness, higher electrophilicity index, and good photovoltaic performance than other sensitizers. The lowest dihedral angle is observed in A1, A2, A6, A7, and A8 which are appropriate for intramolecular charge transfer between the molecules. The A8 has higher light harvesting efficiency, which increases the photovoltaic efficiency of the designed dye. The A6, A7, and A8 dyes spend less time in the excited state, which means they emit photons more efficiently than other dyes. The interaction between donor to π-spacer (red line) parts of the dyes has the bonding interaction (positive), and π-spacer to acceptor (blue line) parts of the dyes have the bonding and antibonding (negative) behaviours. The dyes A5 and A9 have 305.79 and 357.71 times higher β0 values than urea (0.781 × 10-30 esu) molecules. The spectral properties of the A6 dye strongly affect the structural modification. The density functional theory (DFT) and time-dependent DFT (TD-DFT) approach B3LYP/6-311G (d,p) basic set were used to optimize the designed dyes. All the calculations are performed using Gauss view 6.0 and Gaussian 09 software. The density of state spectrum is plotted using Gauss sum 2.6.

First-Principles DFT Study of the Molecular Structure, Spectroscopic Analysis, Electronic Structures and Thermodynamic Properties of Ascorbic Acid

We present an analysis of the optimized geometry, vibrational spectroscopic frequencies, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gap, global reactivity parameters, molecular electrostatic potential (MEP), electrostatic potential (ESP), electronic density (ED), density of states (DOS), Mulliken charges and thermodynamic properties of Ascorbic acid (C6H8O6) using the density functional theory (DFT) with B3LYP/6-311G(d,p) basis set. Various vibrational modes including C-C and C-H stretching vibrations were observed and identified. Along with these, in-plane C-H bending vibrations were also detected within the range of 3000-3100 cm-1. Analysis of the calculated HOMO and LUMO energies revealing insights into its chemical stability and reactivity and inform significant charge transfer phenomenon with an energy gap of 5.6545 eV between them within the molecule. The DOS spectrum provided additional clarity on the energy levels of orbitals, complementing with our HOMO-LUMO analysis. The global reactivity parameters i.e. hardness, chemical potential, electronegativity, chemical softness and electrophilicity index were determined to be 2.8272 eV, -3.9892 eV, 3.9892 eV, 0.3481 eV⁻¹ and 2.8143 eV respectively suggesting valuable information on its chemical reactivity and interaction potential. Visualizations of ESP, MEP and ED offered a deeper understanding of its molecular interactions and charge distribution. The Mulliken charges analysis indicated that most of the carbon atoms except C10 and all the hydrogen atoms show positive charge while all the oxygen atoms together with C10 show the negative charges emphasizing key regions of positive and negative charge localization. Among them, C1 and O8 atoms have the highest positive and negative charges respectively. Heat capacities at constant volume and at constant pressure, internal energy, enthalpy and entropy were observed to increase with rise in temperature contrasting with the trend observed for Gibbs free energy providing insights into the molecule's behavior under different temperature.

First-principles calculations of ScMC2 (M = Fe, Co, Ni, Cu) ternary carbides: A suitable candidate for shielding purpose

Physical properties of scandium-based ternary ScMC2 (M = Fe, Co, Ni, Cu) carbides have been investigated using first-principles calculations. The Wien2k code based on Density Functional Theory (DFT) is employed for these calculations. The study validates that all examined carbides satisfy the criteria for structural, mechanical, thermal, and thermodynamic stability. Among the four studied carbides, ScCuC2 is found to exhibit the most stable structure. The lengths of carbon-carbon (C-C) bonds differ across the compounds under study. Further, physical properties such as elasto-mechanical, thermal and optoelectronic properties of ternary ScMC2 (M = Fe, Co, Ni, Cu) carbides have been calculated. Stiffness constants and elastic moduli are calculated and compared with previously reported results. Poisson's and Pugh's ratios suggest the ductile nature of ScMC2 (M = Fe, Co, Ni) carbides, while ScCuC2 carbide bears brittle behavior. The thermal shock resistance ranking is ScNiC2> ScCoC2> ScCuC2> ScFeC2. These carbides also show improved thermal properties, machinability, rigidity, melting point, resistance to bond elongation and torsional deformations. DOS (density of states) spectra indicate the metallic behavior of ScMC2 (M = Fe, Co, Ni, Cu) carbides with electronic states decreasing progressively at the Fermi level (EF) with different transition metals. Optical properties reveal anisotropy in ScMC2 carbides up to 30 eV and reflectance spectra suggest that ScCoC2 carbide is the most suitable candidate for shielding and solar heating mitigation among the studied compounds.

Structure, Spectroscopy, and Theoretical insights on Co-crystals of 2,4-Diamino-6-Methyl-1,3,5-Triazine Bis(4-Aminobenzoic acid) Monohydrate as a promising anti-cancer agent

Co-crystals of 2,4-diamino-6-methyl-1,3,5-triazine bis (4-aminobenzoic acid) monohydrate (hereafter named DMTAB) have been grown from a slow solvent method at room temperature. Single crystal XRD reveals the centrosymmetric nature of the grown crystal with the P21/n space group. Hirshfeld Surface analysis has been performed to visualize and analyse the spatial distribution of intermolecular interactions in a molecular system. The presence of functional groups has been analysed with Fourier Transform Infrared and Raman studies. By employing NBO analysis, valuable insights into the nature of chemical bonds, electron delocalization, and the overall stability of molecular systems have been examined. Theoretical UV–Vis spectrum studies using Time-Dependent - Density Functional Theory (TD-DFT) in different solvents provide a valuable computational tool to predict and understand the electronic transitions of molecules. HOMO-LUMO analysis and density of states spectrum in different solvents further shed light on the electronic structure and reactivity of molecules in their surroundings. First-order hyperpolarizability calculations have been used to analyse the nonlinear optical response of a grown material. Molecular docking studies were conducted to anticipate the binding conformation of the DMTAB ligand with the relevant target proteins, specifically the ovarian cancer target (Rad6 ubiquitin-conjugated enzyme [PDB ID: 2YB6]) and breast cancer target (protein kinase CK2 [PDB ID: 6HNY].

Computation insights of kagome structure for probing electronic and thermodynamic properties by applying external factors such as strain, spin-orbital coupling, and external magnetic field

In this study, we explored the electronic properties of a two-dimensional (2D) kagome lattice in the presence of an external magnetic field, spin-orbit coupling (SOC), and strain. Our focus was on investigating the energy-dependent behavior of the electronic heat capacity and paramagnetic spin susceptibility in response to changing factors. Employing the Green's function approach, we successfully determined the energy dependence of the electronic heat capacity and paramagnetic susceptibility using the tight-binding model. Notably, at low energies, the electronic heat capacity almost reaches the Schottky anomaly peak, while the paramagnetic susceptibility sharply decreases. Furthermore, we conducted a detailed investigation of the energy-dependent paramagnetic susceptibility and electronic heat capacity of a kagome lattice monolayer, considering the influences of SOC and magnetic field factors. Our investigation of the density of states (DOS) in the presence of SOC suggests that semimetal-to-insulator phase transitions occur. Additionally, throughout our study, we observed variations in the DOS spectrum, indicating the influence of both compressive and tensile strains. We found that these alterations, along with the splitting of levels under different conditions, led to changes in the material's electrical properties.

Performance analysis of carbon nanotube and graphene nanoribbon based biochemical sensors at atomic scale

Advancements in fabrication technologies have led to the possibility of synthesizing atomic-scale graphene nanoribbon (GNR) and carbon nanotube (CNT) based nanodevices. The purpose of this study was to model the electronic properties and electrical characteristics of these devices by atomistic modeling using density functional theory and the non-equilibrium Green’s function and compare the effects of molecular functionalization and sensing. The potential profile of the device was computed using the three-dimensional Poisson equation for smaller applied bias within one voltage range. Simulations showed a bandgap of 1 eV for armchair GNRs (AGNRs), which were insensitive to functionalized amine molecules, resulting in fewer alterations in the density of states (DoS), transmission spectra and the device current (ΔI). The bandgap further increased to 2 eV upon rolling the GNR into a armchair CNT (ACNT), which further decreased sensitivity. However, changing the configuration of the AGNR to a zigzag GNR (ZGNR) led to remarkable changes in the DoS and transmission spectra and a significant improvement in sensitivity. This improvement increased by 1.5–2 times upon rolling the ZGNR into a zigzag CNT (ZCNT). Thus, at lower dimensions in atomic scale, we found an alteration in device current of the carbon structures that was directly proportional to sensitivity in the following order: ΔI ACNT < ΔI AGNR < ΔI ZGNR < ΔI ZCNT. However, the same was found to fall for ZGNR and ZCNT with an increase in width to length (W/L) ratio. This highlights the importance of smaller atomic structures and this work provides a guideline for effective utilization of these structures for biochemical sensing.

Sensing ability of carbon nitride (C6N8) for the detection of carbon monoxide (CO) and carbon dioxide (CO2)

Carbon nitride (C6N8) is explored as an adsorption material for harmful industrial gases such as carbon monoxide (CO) and carbon dioxide (CO2). The complexation of CO and CO2 with C6N8 (analyte@C6N8) is deeply studied by the analyses of interaction energy (IE), frontier molecular orbital (FMO), non-covalent interactions (NCI), natural bond orbital (NBO), Bader’s quantum theory of atoms in molecules (QTAIM), density of state (DOS), reduced density gradient (RDG), and electron localization function (ELF). The results of interaction energy (−18.870 kJ/mol to −14.991 kJ/mol) showed the adsorption strength of CO and CO2 gases on the C6N8 surface. NCI and QTAIM investigations demonstrated that non-covalent interactions occurred in CO2 @C6N8 and CO@C6N8 complexes. The NCI and RDG analyses indicated surface interaction with CO and CO2 gases. The emergence of novel energy levels in the DOS spectrum highlighted the system's susceptibility to contaminants and the development of new excited states in the PDOS spectrum demonstrated the chemical reactivity of complexes. Moreover, the results of QNBO show that surface (C6N8) extracted a relatively greater amount of charge from CO (0.018 e−1) as compared to CO2 (0.006 e−1). At 300 K, the analyte@C6N8 complexes recovery time (4.06 ×10−10 s and 1.92 ×10−9 s) showed sensing behavior of surface for CO and CO2 gases. Our results suggested that the C6N8 surface is a superb option for CO and CO2 gases.

In silico investigation on sensing of tyramine by boron and silicon doped C60 fullerenes

The present communication deals with the adsorption of tyramine neurotransmitter over the surface of pristine, Boron (B) and Silicon (Si) doped fullerenes. Density functional theory (DFT) calculations have been used to investigate tyramine adsorption on the surface of fullerenes in terms of stability, shape, work function, electronic characteristics, and density of state spectra. The most favourable adsorption configurations for tyramine have been computed to have adsorption energies of − 1.486, − 30.889, and − 31.166 kcal/mol, respectively whereas for the rest three configurations, it has been computed to be − 0.991, − 6.999, and − 8.796 kcal/mol, respectively. The band gaps for all six configurations are computed to be 2.68, 2.67, 2.06, 2.17, 2.07, and 2.14 eV, respectively. The band gap of pristine, B and Si doped fullerenes shows changes in their band gaps after adsorption of tyramine neurotransmitters. However, the change in band gaps reveals more in B doped fullerene rather than pristine and Si doped fullerenes. The change in band gaps of B and Si doped fullerenes leads a change in the electrical conductivity which helps to detect tyramine. Furthermore, natural bond orbital (NBO) computations demonstrated a net charge transfer of 0.006, 0.394, and 0.257e from tynamine to pristine, B and Si doped fullerenes.

First-principles calculations to investigate Structural, mechanical, electronic, magnetic and thermoelectric properties of MRh2O4 (M = Mg, Mn, Cd) spinel oxides

Structural, mechanical, magnetic, electronic and thermoelectric properties of MRh2O4 (M = Mg, Mn, Cd) spinel oxides are studied through first-principles calculations. Calculations of structural and elastic stiffness constants (Cij’s) show that the MRh2O4 oxides are stable structurally and mechanically. Elastomechanical results show that the CdRh2O4 is ductile, MnRh2O4 is brittle, while MgRh2O4 lies on the borderline differentiating the ductile and brittle character. MnRh2O4 has high bulk modulus and high Young’s modulus which indicate its ability to resist plastic deformation. MnRh2O4 spinel oxide bears the highest values of Debye temperature (TD = 634.4 K) and melting temperature (Tm = 3530.4 K) among the MRh2O4 (M = Mg, Mn, Cd) oxides. Band structure calculations and density of states spectra indicate the p-type semiconducting nature of MRh2O4 (M = Mg, Mn, Cd) oxides. Spin-polarized electronic structure of CdRh2O4 show 100 % spin-polarized behavior, while MgRh2O4 and MnRh2O4 oxides show 0.12 % and 0.29 % spin-polarization, respectively. MnRh2O4 exhibits saturation magnetization Ms = 172 emu/g and total magnetic moment mtot = 9.99 µB/f.u. Temperature dependent thermoelectric properties (thermal conductivity, electrical conductivity, Seebeck coefficient, Hall coefficient, power factor and figure of merit) are also studied for MRh2O4 oxides. Calculated thermoelectric properties of MRh2O4 (M = Mg, Mn, Cd) oxides show that these oxides are promising for applications as novel thermoelectric materials.

Synthesis, structural and X-ray analysis evaluations and computational studies of newly tetrahydroisoquinoline derivatives as potent against microsomal prostaglandin E synthase 1

Tetrahydroisoquinolines (THIQs) are a significant class within the broad range of natural compounds known as isoquinoline alkaloids. Natural and manmade drugs based on THIQ have a variety of biological effects that protect against different infectious pathogens and neurological diseases. In this study, two new THIQ derivatives were synthesized and characterized using by X-ray crystallographic analysis. The performed Hirshfeld analysis shows the intermolecular interactions and reactive sites of compounds. The 2D fingerprints reveal dominants H···C interactions up to 8.8% in 3a while 43% H···H elemental interactions are observed in compound 3b. In studied compound 3a, the repulsion energies (k-rep) dominate the other energies where the highest amount of 63.8 kJ/mol is obtained whereas 3b has a significant contribution from E-dis to the total energy of the molecule from the energy framework study. Moreover, the density functional theory study reveals better thermodynamic and electronic stabilities. These compounds have reduced HOMO-LUMO gaps (EH-L) ranging from 3.66 to 3.60 eV, indicating their remarkable conductive and electronic properties. The significant reduction in EH-L also guarantees our synthesized compounds’ soft nature and reactivity. Our studied compound’s NBO charges and MEPs analysis show electron-rich sites and donor–acceptor mechanism. Our synthesized compounds have remarkable polarizability (αo) and hyperpolarizability (βo) values (446.23 − 1312.73 au), which indicates their optical and nonlinear optical properties. The density of states spectra further illustrates their notable structural-electronic properties and reduced band gaps. Based on structural activity relationship studies, we found that these tetrahydro-isoquinolines derivatives are potent against microsomal prostaglandin E synthase 1(MPGES1), the docking analysis shows that studied compounds have a good binding affinity with MPGES1, and further ADME/T analysis was carried out for both compounds. In addtion to this molecular dynamics, studies were performed to understand the binding stability of both compounds in protien complex system during 100 ns simulation. Communicated by Ramaswamy H. Sarma

Histamine sensing by boron and silicon doped C60 fullerenes: A first principles investigation

The present study reports adsorption mechanism of histamine on the surfaces of pure, B- or Si-doped fullerenes. The adsorption of histamine on pure and doped fullerenes has been investigated through density functional theory calculations in the terms of stability, geometry, work function, electronic properties, and density of state spectra. The magnitude of adsorption energies has been computed to be −1.66, −35.29, and −37.43 kcal/mol for histamine corresponding to the most favorable adsorption configurations respectively. The band gap analysis revealed that the electrical conductivity of pure fullerene remains nearly constant even after histamine adsorption. However, the doping of boron and silicon leads to the decrease of the band gap after histamine adsorption resulting increment in the electrical conductivity which infers that boron and silicon doped fullerenes are more sensitive towards histamine adsorption than pure fullerene. Moreover, the NBO calculations showed charge transfer of 0.008, 0.409, and 0.272e from histamine to pure, boron and silicon doped fullerenes in the most favorable adsorption configurations, respectively.

Investigate the ability of deep eutectic solvent (ChCl-glycerol) to sense the sulphur dioxide using density functional theory calculations and molecular dynamics simulations

SO2 gas is one of the major industrial pollutants, by-product obtained from the combustion of fossil fuels, is an indirect greenhouse gas. Hence, deep eutectic solvent can offer an inexpensive and efficient way for its sensing and removal. A theoretical investigation for deep eutectic solvent (DES) consisted of choline chloride and glycerol has been done with density function theory (DFT) calculations. DES was investigated for adsorption of SO2. Herein, feasibility of adsorption ability of the DES for different concentration or amount of SO2 was performed; on varying the ratio of DES: SO2 from 1:1 to 1:4. The change in feasibility of interaction of the DES and SO2 was also studied with the change in temperature using DFT computation. The study was done by analyzing the interactions, thermodynamic properties obtained from DFT calculations. The stability & interaction between DES and SO2 as well as the extent of charge transfer was analyzed with the help of natural bond orbital (NBO) analysis and density of states spectra (DOS). Molecular dynamic (MD) simulations of the DES and DES:SO2 (1:1 to 1:4) were performed and the interactions were analyzed using root mean square deviation (RMSD), root mean square fluctuation (RMSF) and radial distribution function (RDF). It was observed that the DES exhibited most stable interactions in the gaseous state. DES in gaseous state exhibited very stable interaction with the SO2 molecule as the concentration of the SO2 was increased the stability of interaction was also observed to increase. With the increase in temperature, the feasibility of interaction between DES and SO2 decreases.

Fluorine derivatives of piceatannol for photobiological and photophysical applications by DFT approach

In the present work, we have calculated the electrical and optical properties of pure piceatannol (PI) and its six fluorinated derivatives (F1-F6). The first-principles calculations are performed in the framework of density functional theory employing the full-potential linearized augmented plane wave (FP-LAPW) method using PBE-GGA. It is found that the PI and its F-substituted derivatives are semiconductors with a HOMO-LUMO bandgap of 0.38 to 2.29 eV. Calculated partial density of states (DOS) of carbon and oxygen atoms show that the nature of C-O bonds is polar at PI. The effect of F substitution on the bandgap of PI are analyzed by comparing the DOS spectra. The size of the band gap can be controlled by changing the F sites in the PI. It is found that the band gap value decreases by substation of F at the F1, F2, F3, and F4 sites along with the F-O bonds at the LUMO state. However, in F5 and F6 sites, the change of the band gap is not significant. The dielectric behavior of the PI is observed at the y-direction. The calculated dielectric function spectra show the optical anisotropy at the x and the y-directions. The optical spectra revealed that F substitution in PI led to reduction of the optical band gap values and a red-shift occurs in the absorption spectra. The calculated absorption spectra of PI are in good agreement with the experimental data.

Investigation of heterostructures based on hafnium oxide

We presented ab initio calculations of bulk structures and thin films of hafnium oxide, and heterostructures based on hafnium oxide in the tetragonal phase and silicon, structural and electronic properties are investigated. The density of states spectra is considered, the results obtained are analyzed, and some of them are compared with previously obtained data (for the studied systems).

The molecular level study of the fate of the CH3CH2C(O)OCH(O)CH3 radical derived from ethyl propionate

ABSTRACT A quantum chemical study has been presented on the decomposition of CH3CH2C(O)OCH(O • )CH3 which is derived from ethyl propionate (CH3CH2C(O)OCH2CH3) using the M06-2X/6-31 + G(d,p) level of theory. The thermal decomposition of CH3CH2C(O)OCH(O • )CH3 is essential to understand the chemistry of combustion of ethyl propionate. Here, the decomposition and oxidative pathways, bond fission and alpha ester rearrangement of CH3CH2C(O)OCH(O • )CH3 have been explored. We have obtained transition states for the different pathways and further verified each transition state by performing intrinsic reaction coordinate (IRC) calculations. The density of state spectra (DOS) was calculated using GaussSum software. The single-point energy calculations are performed at the same function but using larger basis sets such as 6-311++G(d,p) and 6-311++G(3df,2p). We have shown all stationary points and transition states involved in reaction pathways on the potential energy surface (PES) diagram and also discussed the thermochemistry of each reaction pathway. The thermal rate constants of various channels in the decomposition of CH3CH2C(O)OCH(O • )CH3 are determined using the Conventional Transition State Theory (CTST) in the temperature range of 250–450 K and 1atm. From PES, thermochemistry and kinetics analysis, we found that α-ester rearrangement produces propionic acid, which is dominant over the oxidative pathway for the decomposition of CH3CH2C(O)OCH(O • )CH3.

A DFT modulated analysis of manganese doped graphene nanoribbons as a potential material for sensing of highly toxic gases CO, PH3 and SbH3

A theoretical Density-functional theory (DFT) study has been carried out to explore the interaction of highly toxic gases carbon monoxide (CO), phosphine (PH3) and stibine (SbH3) with pristine (AGNR) and manganese (Mn) doped armchair graphene nanoribbon (AGNR-Mn). The adsorption behaviour of these gases has been analyzed by calculating the binding distance, adsorption energy (Eads), band structure, density of state spectrum, and current-voltage characteristics. In the case of AGNR, the highest Eads = −0.19 eV has been observed for the CO gas. The Mn doping leads to the high stability and substantial improvement in adsorption performance due to covalent interaction with gas molecules. The enhancement in adsorption energy by 19, 26 and 23 times for CO, PH3 and SbH3 respectively has been observed using AGNR-Mn instead of AGNR. The adsorption of these gases shows a considerable enhancement in the DOS around Fermi level. Furthermore, using I-V characteristics, the response of all these gases is observed and it has been found that the response of PH3 and SbH3 gas to AGNR-Mn are 48% and 45% respectively. These findings indicate that the AGNR-Mn system can be explored as a highly sensitive material for potential gas sensing of PH3 and SbH3.

Energy spectrum and light absorption of arsenene quantum dots

As a close relative of phosphorene, puckered arsenene is stable and has been demonstrated experimentally as a promising two-dimensional semiconductor material. By means of a multi-orbital tight-binding model, we investigate theoretically the energy spectrum and magneto-optical properties of circular and rectangular arsenene quantum dots (AQDs). The tight-binding parameters are obtained by reproducing accurately the electron energy bands of puckered arsenene from the first-principle calculation. For both AQDs, the density of states (DOS), probability distribution and inverse participation ratio (IPR) of eigenstates, and optical absorption spectrum are calculated numerically. It is found that edge states of AQDs fill up the bulk band gap of puckered arsenene and are only localized near the armchair edges of AQDs. These features differ greatly from those in quantum dots made of graphene or phosphorene. The band edges of arsenene monolayer can be located roughly from the IPR and DOS spectrum. The light absorptivity of both AQDs under zero magnetic field depends strongly on the polarization direction of incident light. The position and intensity of absorption peaks can be tuned by the shape of quantum dots and the applied magnetic field. The anisotropy ratio of light absorption can be reduced by one order of magnitude under a magnetic field of tens of Tesla.