Amount Of Charge Transfer Research Articles

The binding mechanism of ivermectin and levosalbutamol with spike protein of SARS-CoV-2.

In this study, we have investigated the binding mechanism of two FDA-approved drugs (ivermectin and levosalbutamol) with the spike protein of SARs-CoV-2 using three different computational modeling techniques. Molecular docking results predict that ivermectin shows a large binding affinity for spike protein (− 9.0 kcal/mol) compared to levosalbutamol (− 4.1 kcal/mol). Ivermectin binds with LEU492, GLN493, GLY496, and TRY505 residues in the spike protein through hydrogen bonds and levosalbutamol binds with TYR453 and TYR505 residues. Using density functional theory (DFT) studies, we have calculated the binding energies between ivermectin and levosalbutamol with residues in spike protein which favor their binding are − 22.4 kcal/mol and − 21.08 kcal/mol, respectively. The natural bond orbital (NBO) charge analysis has been performed to estimate the amount of charge transfer that occurred by two drugs during interaction with residues. Molecular dynamics (MD) study confirms the stability of spike protein bound with ivermectin through RMSD and RMSF analyses. Three different computer modeling techniques reveal that ivermectin is more stable than levosalbutamol in the active site of spike protein where hACE2 binds. Therefore, ivermectin can be a suitable inhibitor for SARS-CoV-2 to enter into the human cell through hACE2.

Be2+ and Mg2+-decorated sulflower: Potential systems for molecular hydrogen storage

The hydrogen binding efficiency of multiple metal-ion (Be2+, Mg2+)-decorated “First Generation” Sulflower (C16S8) systems has been investigated for the first time using density functional ω-B97XD method and 6311++G(d,p) basis set. Our calculations show that the central ring of the aforesaid system can be decorated by a single di-positive metal ion, followed by favorable decoration of at most one pair of metal ions (di-positive each) on the peripheral five-membered rings, both on same and opposite faces with certain preferences. All of the metal ion-decorated complexes are capable of efficient hydrogen binding. Be2+ and Mg2+-decked single ion complexes effectively bind six and four H2 molecules respectively. Moreover, each of the double ion-decorated systems can adsorb ten H2 molecules irrespective of the facial orientation of the metal ions. The average interaction energy (ΔE) between sulflower and metal ions (single and double ions) as well as the average binding energy (ΔBE) per molecular hydrogen of the concerned metal-ion-decorated complexes is found to be much higher for Be2+-decked systems. The nature of interaction between hydrogen molecules and metal ions is explicated by the topological analysis (AIM Analysis) and NBO formalisms. In case of Be2+-decked systems, the amount of charge transfer from H2 bonding orbital to metal anti-bonding orbital is much higher than analogous Mg2+-decorated systems. The Natural Population Analysis (NPA) evaluates the charge variation on the acceptor metal ions due to hydrogen adsorption. In short, our theoretical study gives a comprehensive account of the relationship between the metal ion-decorated sulflower systems and hydrogen molecules, which will further motivate researchers in the field of efficient hydrogen storage materials.

A computational study on the novel defects of graphene quantum dot as a promising anode material for sodium ion battery

The existence of defects in the graphene quantum dots can alter their electronic properties. In this study, the interaction of sodium ion/atom with defected graphene quantum dots (dGQDs) of F3.Gr, F3H3.Gr, N3.Gr and N3H3.Gr as the anode material for the sodium ion batteries was investigated using density functional theory calculations. The amount of charge transfer from Na atom to F3H3.Gr and from F3.Gr to Na ion is about 0.23 and 0.94|e|, respectively. In the complex of Na atom with dGQDs as an n-type-adsorbed dGQD, the Fermi level shifts towards the higher energy and it can be facilitated charge transfer from Na atom to dGQDs. The estimated electrical conductivity for the complexes of Na atom with F3.Gr and F3H3.Gr is 6.51 × 10−13 and 5.26 × 10−12, respectively. This can result in a favorable condition in the processes of battery charge and discharge. The cell voltage belonging to F- doped defects or N- doped defects is nearly 1.54–1.58 V or 0.58–0.61 V. It is concluded that the F- doped defects are more promising anode material for sodium ion batteries compared to N- doped defects because of their lower recovery time of adsorption, higher voltage, higher reactivity and better charge transfer.

DFT studies of single and multiple alkali metals doped C24 fullerene for electronics and nonlinear optical applications

The geometric, electronic and nonlinear properties of exohedral and endohedral single and multiple alkali metal (Li, Na and K) atom doped C24 fullerene are studied. First, the most stable orientations at the most stable spin state are evaluated. Complexes with odd metal atoms are stable at doublet spin state and complexes with even number of metal atoms are stable at singlet spin state. Thermodynamic analysis shows that Li4C24 among all complexes with highest thermodynamic stability has interaction energy of −190.78 kcal mol−1. The energy gaps (GH-L) are fairly reduced in single and multi-doped cages, and the lowest energy gap is observed for K4C24 complex. NBO analysis is performed to validate the charge transfer from alkali metal toward C24. The largest amount of charge (0.95 |e|) transfer is monitored in exohedral K2C24 complex where the highest charge transfer is for potassium (K) metal. Total density of states (TDOS) spectra of doped complexes justify the involvement of alkali metals and nanocage in new HOMO formation for the excess electrons. First hyperpolarizability is descriptor of NLO properties of single and multi-doped complexes are calculated. It is observed that doping of alkali metal atoms (Li, Na and K) greatly enhances the first hyperpolarizability. Among all the complexes of C24, Na3C24 shows the highest hyperpolarizability value of 2.74 × 105 au. The results of this study are a guideline for the computational designing of highly efficient and thermodynamically stable complexes for the optical and optoelectronic technologies.

Utilizing complex oxide substrates to control carrier concentration in large-area monolayer MoS2 films

Bandgap engineering is central to the design of heterojunction devices. For heterojunctions involving monolayer-thick materials like MoS2, the carrier concentration of the atomically thin film can vary significantly depending on the amount of charge transfer between MoS2 and the substrate. This makes substrates with a range of charge neutrality levels—as is the case for complex oxide substrates—a powerful addition to electrostatic gating or chemical doping to control the doping of overlying MoS2 layers. We demonstrate this approach by growing monolayer MoS2 on perovskite (SrTiO3 and LaAlO3), spinel (MgAl2O4), and SiO2 substrates with multi-inch uniformity. The as-grown MoS2 films on these substrates exhibit a controlled, reproducible, and uniform carrier concentration ranging from (1–4) ×1013 cm−2, depending on the oxide substrate employed. The observed carrier concentrations are further confirmed by our density-functional theory calculations based on ab initio mismatched interface theory (MINT). This approach is relevant to large-scale heterostructures involving monolayer-thick materials in which it is desired to precisely control carrier concentrations for applications.

Electronic properties of donor:acceptor complexes in all-polymer solar cells based on density functional theory

The electronic properties at the donor (D):acceptor (A) interface are a crucial factor in determining the efficiency of organic photovoltaic devices. Here, based on first-principles calculations, the electronic properties of ten configuration complexes composed of D polymer PDPPTPT and A polymer PNDI2OD-TVT were simulated. Results show that the bandgap values of the homo-/heterojunctions decrease with the increase of the number of molecular layers, and that of AAA is close to zero. This indicates that the homogeneous stacking is favorable for charge transport; furthermore, the bandgap of the complexes is affected by the molecular arrangement. Through the differential charge density and Bader charge analysis method, it was found that charge transfer will occur intermolecularly, which promotes the formation of a dipole moment at the D:A interface, and the dipole electric field then helps the dissociation of excitons in the active layer. The amount of charge transfer at the D:A interface in the DDA, DAA and DDAA configurations is about twice that in the DA configuration alone, demonstrating that homogeneous accumulation in complexes can enhance the interface dipole interaction. The comprehensive analysis suggests that homogeneous accumulation is conducive to charge transport, that heterogeneous stacking helps to promote exciton dissociation, and that there should be an optimal ratio. Furthermore, the dipole electric fields formed at the D:A interface exhibit the characteristics of local and non-uniform distribution.

Electronic charge transfer during metal/SiO2 contact: Insight from density functional theory

Contact charging of hydroxylated SiO2/metal interfaces is studied using density functional theory calculations. Atomic scale models are generated for hydroxylated α-cristobalite interfaced with three different fcc metals: Al, Pt, and Au. Regions of electron accumulation and depletion are highest in magnitude near the SiO2/Pt and SiO2/Au interfaces and lower at the SiO2/Al interface. One key finding of this work is that the presence of a metal surface near the hydroxylated SiO2 induces electronic states at the SiO2 surface within the apparent insulating bandgap. The magnitude of these states is highest for Pt and Au contacts and lowest for Al, indicating that the amount of charge transfer at the interface trends with the density of electronic defect states. Such electronic defect states reside near the fermi level of the system and it is proposed that these states from surface oxygen atoms are at least partly responsible for the electronic charge transfer mechanism between a metal and an insulator.

The interaction of two-dimensional P2SiS nanosheet with environmental toxic NCG molecules for sensor application: A DFT study

Gas sensors are vital ingredient substances for the detection of gas molecules on two-dimensional material due to their high surface-to-volume ratios. In this context, we have performed the environmentally toxic gas molecules sensing properties for NCG (NH3, NO2, and NO) molecules adsorbed on the 2D P2SiS nanosheet using density functional theory and NEGF approach. The significant effects are shown through the variation in adsorption strength, electronic properties, charge transfer, conductivity, work function, and recovery time. It is found that NH3 and NO molecules show physisorption through van der Waals forces, whereas NO2 prefers chemisorption on the P2SiS surface. We observed that at room temperature, NH3 and NO molecules exhibit a very short recovery time of 2.49 μs and 3.6 μs, respectively, while the same is noted to be quite large for the NO2 gas molecule. The amount of charge transfer found to be -0.03e, 0.74e, and 0.15e for NH3, NO2, and NO, respectively. The frequency calculation has also confirmed that structures belong to true local minima. NH3 molecule performs as the charge accepter, whereas NO and NO2 are noticed to donate charge to the 2D P2SiS nanosheet. Moreover, a superior I–V response and sensitivity of NCG molecules towards the 2D P2SiS nanosheet is also revealed in the present study. Thus, we suggest that 2D P2SiS nanosheet may be used as a highly sensitive and multi-time reusable gas sensor material for NH3 and NO gas molecules, whereas disposable gas sensor material for NO2 molecule.

Systematic optimization of triboelectric nanogenerator performance through surface micropatterning

Abstract Since the first papers on triboelectric nanogenerators (TENG) were published in 2012, the performance and efficiency of these novel devices have continued to improve dramatically. Early on, it was found that adding nanostructures to the surfaces of the active materials improved the efficiency as it increased the surface area and thus the amount of charge transfer. While this method of optimization makes logical sense, there has been little systematic work to show exactly how the increased surface area improves TENG performance. Here we propose a simple geometric model showing how arrays of hemispheres can interlock with each other and increase the amount of surface contact based on the spacing between pattern features. We were able to correlate this with a polyamide and polyvinylidene fluoride (PVDF) model system TENG which were patterned using a method based on hot microcontact printing. By tuning the spacing between the pattern features, the output voltage and current can be improved by several times compared to a planar sample. By deepening our understanding of the surface interactions in TENG we can optimize TENG devices in smarter ways to reduce cost and improve performance.

Helium-nitrogen mixtures at high pressure

The energy landscape of helium-nitrogen mixtures is explored by ab initio evolutionary searches, which predicted several stable helium-nitrogen compounds in the pressure range from 25 to 100 GPa. Among these high-pressure compounds, the monoclinic structure of ${\mathrm{HeN}}_{22}$ consists of neutral He atoms, partially ionic dimers ${\mathrm{N}}_{2}^{\ensuremath{\delta}\ensuremath{-}}$, and lanternlike cages ${\mathrm{N}}_{20}^{\ensuremath{\delta}+}$, showing a certain amount of charge transfer within the nitrogen framework. The monoclinic (${\mathrm{HeN}}_{20}{)}^{\ensuremath{\delta}+}{\mathrm{N}}_{2}^{\ensuremath{\delta}\ensuremath{-}}$ may be quenchable to ambient pressure with the estimated energy density of 10.44 kJ/g, which is $\ensuremath{\sim}2.4$ times larger than that of trinitrotoluene, indicating a very promising high-energy-density material.

Theoretical modification of C24 fullerene with single and multiple alkaline earth metal atoms for their potential use as NLO materials

Density functional theory (DFT) calculations have been performed for the single and multi-alkaline earth metal atoms doped C24 fullerene. All possible orientations have been optimized with different spin states to achieve the most stable geometry. Be4@C24 shows the highest interaction energy of −182.87 kcal mol−1 among all complexes. The H-Lgap is increased in single doped complexes but is fairly reduced in all multi-doped cages, and the lowest H-Lgap is observed for Mg4@C24 (0.83 eV) which indicates the conductor behavior of this newly designed complex. NBO analysis is performed to confirm the charge transfer from metal toward the cage. The largest amount of charge (1.18 |e|) transfer has been observed for endohedral Mg@C24 nanocage. Involvement of new HOMO orbitals (due to excess electrons) is confirmed from total density of states (TDOS) spectra of doped cages. It was observed that doping of alkaline earth metal atoms (Be, Mg and Ca) greatly enhanced the first hyperpolarizability. Among all these AEMn@C24 (AEM = Be, Mg and Ca, n = 1, 2, 3, 4) cages, Mg4@C24 shows the highest hyperpolarizability value of 3.62 × 106 au with H-Lgap of 0.83 eV. The results of this study provide a guideline for the synthesis of highly efficient and thermodynamically stable nanocages for the optical and optoelectronic applications.

Theoretical study on water adsorption and dissociation on the nickel surfaces.

Using density functional theory methods, H2O dissociation was investigated on the Ni(111), Ni(100), and Ni(110) surfaces. H and O atom as well as OH species adsorb stably at the high coordination sites. While on the Ni(110) surface, the OH species prefers at the twofold short bridge site because the adsorption on the fourfold hollow site is less feasible due to the increased distances between the nickel atoms. The amount of charge transfer is related to the adsorption stability. The more charge transfer, the more stable the adsorption. The charge transfer decreases in the order of O > OH > H. H2O molecule adsorbs at the top site in a configuration parallel to the surface. The final products are different for H2O dissociation due to the different mechanisms. On the Ni(111) surface, the final product is the O atom. On the Ni(100) and Ni(110) surfaces, the most abundant species are OH and H, but the reaction mechanisms were different. It is not necessary to linear BEP relationship for a given reaction on different surfaces. These results could provide fundamental insights into water behaviors and a favorable theoretical basis for further understanding and research on the interaction between water and metal surfaces.

Determining Partial Atomic Charges for Liquid Water: Assessing Electronic Structure and Charge Models.

Partial atomic charges provide an intuitive and efficient way to describe the charge distribution and the resulting intermolecular electrostatic interactions in liquid water. Many charge models exist and it is unclear which model provides the best assignment of partial atomic charges in response to the local molecular environment. In this work, we systematically scrutinize various electronic structure methods and charge models (Mulliken, natural population analysis, CHelpG, RESP, Hirshfeld, Iterative Hirshfeld, and Bader) by evaluating their performance in predicting the dipole moments of isolated water, water clusters, and liquid water as well as charge transfer in the water dimer and liquid water. Although none of the seven charge models is capable of fully capturing the dipole moment increase from isolated water (1.85 D) to liquid water (about 2.9 D), the Iterative Hirshfeld method performs best for liquid water, reproducing its experimental average molecular dipole moment, yielding a reasonable amount of intermolecular charge transfer, and showing modest sensitivity to the local water environment. The performance of the charge model is dependent on the choice of the density functional and the quantum treatment of the environment. The computed molecular dipole moment of water generally increases with the percentage of the exact Hartree-Fock exchange in the functional, whereas the amount of charge transfer between molecules decreases. For liquid water, including two full solvation shells of surrounding water molecules (within about 5.5 Å of the central water) in the quantum chemical calculation converges the charges of the central water molecule. Our final pragmatic quantum chemical charge-assigning protocol for liquid water is the Iterative Hirshfeld method with M06-HF/aug-cc-pVDZ and a quantum region cutoff radius of 5.5 Å.

First principles study of atomic adsorption on (111) and (100) surfaces of iridium

We have investigated the adsorption of nine different adatoms on the (111) and (100) surfaces of Iridium (Ir) using first principles density functional theory. The study explores surface functionalization of Ir which would provide important information for further study of its functionality in catalysis and other surface applications. The adsorption energy, stable geometry, density of states and magnetic moment are some of the physical quantities of our interest. The study reveals that the three-/four-fold hollow site is energetically the most favorable adsorption site on the (111)/(100) surface of Ir. The investigation on a wide range of coverages (from 0.04 to 1 monolayer) reveals the strong coverage dependence of adsorption energy of the adsorbate atoms. The adsorption energy is found to increase as the coverage increases, implying a repulsive interaction between the adsorbates. Strong hybridization between the adsorbates and the substrate electronic states is revealed to impact the adsorption, while the magnetic moment of the adsorbates is found to be suppressed. The Bader analysis reveals significant amount of charge transfers between the adsorbate atoms and the substrate. The binding of adsorbate atoms on the (100) surface is observed to be moderately stronger as compared to that on the (111) surface.

Dependency of solvation effects on metal identity in surface reactions

Solvent interactions with adsorbed moieties involved in surface reactions are often believed to be similar for different metal surfaces. However, solvents alter the electronic structures of surface atoms, which in turn affects their interaction with adsorbed moieties. To reveal the importance of metal identity on aqueous solvent effects in heterogeneous catalysis, we studied solvent effects on the activation free energies of the O–H and C–H bond cleavages of ethylene glycol over the (111) facet of six transition metals (Ni, Pd, Pt, Cu, Ag, Au) using an explicit solvation approach based on a hybrid quantum mechanical/molecular mechanical (QM/MM) description of the potential energy surface. A significant metal dependence on aqueous solvation effects was observed that suggests solvation effects must be studied in detail for every reaction system. The main reason for this dependence could be traced back to a different amount of charge-transfer between the adsorbed moieties and metals in the reactant and transition states for the different metal surfaces.

Synthesis and spectral analysis of (S)-7-(4-chlorophenyl)-6,7-dihydrothiazolo [4,5-d]pyrimidine-2,5(3H,4H)-dione and study of its quantum chemical properties

In this article, synthesis and quantum chemical properties of novel (S)-7-(4-chlorophenyl)-6,7-dihydrothiazolo[4,5-d]pyrimidine-2,5(3H,4H)-dione (CPTHZ) are described. The aim of this synthesis was to obtain biologically active thiazolidinone scaffolds and correlates its quantum chemical properties with its experimental results. The structure of the compound was characterized by using different spectral analysis. The chemical calculations were computed with the help of DFT level of theory using Becke3–Lee–Yang–Parr (B3LYP)) and Coulomb–Attenuated–Method–Becke3–Lee–Yang–Parr (CAM-B3LYP)/6-31G(d,p) basis set. Thermodynamic properties were calculated at diverse temperatures. Various structural and thermodynamic parameters such as electrophilicity, chemical potential, chemical hardness and maximum amount of electronic charge transfer were done for this compound. The local reactivity descriptors showed that most reactive site for nucleophilic attack was C(7). In addition to it, correlation graphs between experimental and calculated values of 1 HNMR and 13 CNMR were also presented

Adsorption of Cs-O on Graphene: Modification of the Anderson–Newns Model for the Calculation of Work Function Variation

A modified Anderson–Newns (A–N) model for calculating the work function and the charge transfer of Cs-O-adsorbed graphene surface with the coverage of adsorbed particles is proposed. The calculation of the length of adsorption bond λ is optimized. The work function and the amount of charge transfer for different coverage of Cs-O molecules are calculated, and the calculated results variations are in reasonable agreement with the experimental data. As coverage θ increases, the amount of charge transfer Z decreases and the work function φ first decreases to a certain value and then increases slightly. When θ = 0.8, the work function φ reaches a minimum value of 0.7.

Designing Noble Benzimidazole-Based Bipolar Hosts for Blue Organic Light-Emitting Diodes Using Thermally Activated Delayed Fluorescence Materials.

We designed a novel thermally activated delayed fluorescence (TADF) host molecules for blue elec-trophosphorescence by combining the electron acceptor benzimidazole (BI) unit and the electron donor acridine derivatives into a single molecular unit based on density functional theory (DFT). We obtained the energies of the first singlet (S1) and the first triplet (T1) excited states of the TADF materials by performing DFT and time-dependent DFT (TD-DFT) calculations on the ground state using dependence on charge transfer amounts for the optimal Hartree-Fock percentage in the exchange-correlation of TD-DFT. The DFT and TD-DFT calculations showed that the large separation between the highest occupied molecular orbital and the lowest unoccupied molecular orbital caused a small difference in energy (ΔEST) between the S1 and T1 states. The host molecules retained a high triplet energy and demonstrated a great potential for use in blue phosphorescent organic light-emitting diodes. The results showed that these molecules are promising host materials for TADF OLEDs because they have a low barrier to hole and electron injection, a balanced charge transport for both holes and electrons, and a small ΔEST.

Водородные связи в молекулярных кристаллах аланина и тирозина: NBO анализ

At present, the theoretical concepts of the hydrogen bond (H-bond) in condensed media, for example, in living systems, biomolecules, are not fully solved. Quantum chemical modeling is used as one of the methods for studying the nature and determining the strength of the H-bond. In this paper, we continue to study the system of hydrogen bonds in molecular crystals of alanine and tyrosine. The dimers of these amino acids were modeled using the DFT method using the B97D functional with bases 6-31++G**. In the framework of NBO analysis, the stabilization energies of the formed hydrogen bond and the value of the transferred charge are calculated. It is shown that in alanine dimers, the main factor affecting the h-bond stabilization energy is the geometric parameters and, first of all, (N-H...O). The binding σ-orbital of the hydrogen bond is the result of the interaction of a hybrid NBO of the lone electron pairs of an oxygen atom and a loosening σ*-NBO N−H bond. The nature of bond formation in all three cases is the same, and the charge transfer value is greater than the value of the bond criterion, which indicates the presence of hydrogen bonds in all analyzed alanine systems. In tyrosine dimers, two H-bonds are formed that are similar in nature, as well as in geometric and energy parameters. The third H-bond is very weak, and the amount of charge transfer indicates its absence. The main interaction between the molecules in the third tyrosine dimer is the H-bond between the –СОО− and –OH groups. It was found that the scheme of formation of hydrogen bonds in molecular crystals of tyrosine is somewhat different from that of alanine.

A Linear Relationship between the Charge Transfer Amount and Level Alignment in Molecule/Two-Dimensional Adsorption Systems.

We systematically study the adsorption of tetrathiafulvalene (TTF), tetracyanoquinodimethane (TCNQ), and tetracyanoethylene (TCNE) on a variety of two-dimensional (2D) monolayers with weak van der Waals (vdW) interactions based on density functional theory. We confirm that TTF can act as an effective donor when its highest occupied molecular orbital (HOMO) level is higher than the conduction band minimum (CBM) state of 2D materials, while TCNQ and TCNE can act as effective acceptors when their lowest unoccupied molecular orbital (LUMO) levels are lower than the valence band maximum (VBM) state of 2D materials. Moreover, our calculations reveal a linear relationship between the charge transfer amount and level alignment between the molecule and 2D monolayer. In other words, the charge transfer is linearly dependent on the energy difference between the HOMO level and 2D CBM state for the donor molecule or the energy difference between the LUMO level and 2D VBM state for the acceptor molecule. The linear relationship indicates that the charge transfer is insensitive to the local binding environments due to the weak vdW interaction. However, the linear relationship cannot be applied to atoms or molecules that are chemisorbed on 2D materials.