Charge Density Difference Calculations Research Articles

NO adsorption on the Os, Ir, and Pt embedded tri-s-triazine based graphitic carbon nitride: A DFT study

In this work, we have studied the adsorption performance of NO gas in the pristine and Os, Ir and Pt embedded g-C3N4 using the density functional theory calculations. It is found that the hexagonal cavity is the most stable site for the embedding of Os, Ir, and Pt on the g-C3N4. The obtained outcomes indicate that NO is physisorbed on pristine g-C3N4 whereas chemisorbed on the Os, Ir, and Pt embedded g-C3N4. The bandgap energy considerably decreases after embedding Os, Ir, and Pt atoms and NO adsorption. Partial density of states plots indicates that embedded metals are a bridge to enhance the hybridization between NO and the g-C3N4. The repositioning of HOMO and LUMO is noticed in the Os, Ir, and Pt embedded g-C3N4. Furthermore, it is observed that Os, Ir, and Pt embedded g-C3N4 are magnetic with total magnetic moments of 3.4037, 2.0476, and 1.6641 μβ correspondingly, which undergoes a significant change after NO adsorption. The Bader charge analysis indicates the acceptor nature of the NO gas molecule further validated the charge density difference calculations. Our calculations reveal that Ir embedded g-C3N4 can be considered an outstanding candidate for sensing NO gas and its elimination from the atmosphere.

Interaction of Grafted Dextrin with a Hematite Surface: Effect of Functional Groups and Molecular Weight

AbstractReactive force field (ReaxFF) based molecular dynamics simulations were performed to study the interaction nature of grafted dextrin with hematite. Nature of interaction further explained by doing periodic density functional theory (DFT) calculations. It was observed that in presence of moisture, the polymer adsorbed on the hematite surface via hydrogen bond formation mediated by water. Upon heating, the interfacial water evaporated and boding interactions with the surface was were established. The oxygens present in the polymer backbone also took part in bonding interactions in addition to −COOH, −OH and −COOCH3 functional groups. The binding energies were estimated as −35.8 (Dextrin), −42.6 (Dextrin grafted with polyacrylic acid) and −38.0 kcal/mol (Dextrin grafted with polyacrylic acid and poly (methyl acrylate)) which indicated chemisorption and effect of molecular weight. Grafted dextrin, having higher molecular weight exhibited stronger interaction and it is anticipated that it will have better thermal stability. Binding energy estimated from DFT calculations as −34.8 kcal/mol. DFT charge density difference calculation showed that the oxygen present in the ring polymer structure also interacted with Fe d‐orbitals.

Enhanced SOx sensing performance of BC3 nanosheets functionalized with Na atoms: A first-principles study

Density functional theory calculations were performed to explore the interaction of gas molecules, including SO2 and SO3 with Na-functionalized C3B monolayers. Firstly, the electronic and geometric properties of Na-adsorbed C3B monolayers were examined to search for the most stable metal functionalized C3B based systems. The Na adatoms prefer the hollow site of the C-hexagon of C3B monolayer. Based on the charge density difference calculations, the electronic densities were depleted on the adsorbed Na metals. Thus, the adsorbed Na metals behave as charge donors. Contrary to the pure C3B monolayer with semiconducting property, the Na-adsorbed systems represent metallic character. The considered SO2 and SO3 gas molecules were adsorbed on the metal site of Na-functionalized C3B nanosheets through weak chemical bonds, which indicates the promising media for gas sensing and adsorption. The effects of van der Waals (vdW) interactions were taken into account for the adsorption of gas molecules on the considered C3B sheets. Thus, our results showed that Na-functionalized C3B sheet is a suitable material for gas sensing in the environment.

Construction of a novel supramolecular self‐assembly photocatalyst for full visible light spectrum photooxidation of phenol

AbstractThe sluggish full visible light response of organic supramolecular catalysts is a challenge that greatly restricts their development in the photocatalytic field. Herein, we successfully fabricated a K, Cl‐codoped Bi2WO6/perylene‐diimide(PDI) catalyst with a novel, general, and facile ultrasound assisted water bath heating method. The UV adsorption onset of K, Cl‐codoped Bi2WO6/PDI is redshifted from 750 to 760 nm compared with that of the heterojunction of Bi2WO6/PDI. Under visible light, the phenol is thoroughly mineralized into CO2 and H2O, and the phenol degradation rate was three times higher than that of pure Bi2WO6/PDI. The electrons transfer from PDI to K‐ and Cl‐codoped Bi2WO6/PDI according to the charge density difference calculation. The built‐in potential of K‐ and Cl‐codoped Bi2WO6/PDI could increase from 2.09 to 5.54 eV. The excellent full visible light spectrum photooxidation of phenol is attributed to the suitably strong built‐in potential at the heterojunction between PDI and K, Cl‐codoped Bi2WO6.

The effects of monovalent metal cations on the crystal and electronic structures of Cs2MBiCl6 (M = Ag, Cu, Na, K, Rb, and Cs) perovskites.

Lead-halide perovskites have attracted much attention over the past decade, while two main issues, i.e., the lead-induced toxicity and materials' instability, limit their further practice in widespread applications. To overcome these limitations, an effective alternative is to design lead-free perovskite materials with the substitution of two divalent lead ions with a pair of monovalent and trivalent metal ions. However, fundamental physics and chemistry about how tuning material's composition affects the crystal phase, electronic band structures, and optoelectronic properties of the material have yet to be fully understood. In this work, we conducted a series of density functional theory calculations to explore the mechanism that how various monovalent metal ions influence the crystal and electronic structures of lead-free Cs2MBiCl6 perovskites. We found that the Cs2MBiCl6 (M = Ag, Cu, and Na) perovskites preferred a cubic double perovskite phase with low carrier effective masses, while the Cs2MBiCl6 (M = K, Rb, and Cs) perovskites favored a monoclinic phase with relatively high carrier effective masses. The different crystal phase preferences were attributed to the different radii of monovalent metal cations and the orbital hybridization between the metal and Cl ions. The calculation showed that all Cs2MBiCl6 perovskites studied here exhibited indirect bandgaps. Smaller bandgap energies for the perovskites with a cubic phase were calculated than those of the monoclinic phase counterparts. Charge density difference calculation and electron localization functional analysis were also conducted and revealed that the carrier mobility can be improved via changing the characteristics of metal-halide bonds through compositional and, thus, crystal structure tuning. Our study shown here sheds light on the future design and fabrication of various lead-free perovskite materials for optoelectronic applications.

Engineering Electronic Structure of Single-Atom Pd Site on Ti 0.87 O 2 Nanosheet via Charge Transfer Enables C–Br Cleavage for Room-Temperature Suzuki Coupling

The palladium (Pd)-catalyzed Suzuki reaction is widely applied in the pharmaceutical industry, where constructing highly active and low-cost Pd sites are impendent. Here, we report the fabrication ...

New donor-acceptor-donor type of organic semiconductors based on the regioisomers of diketopyrrolopyrroles: A DFT study

The present work describes computational studies on structural, electronic, charge transport and photovoltaic properties of donor-acceptor-donor (D-A-D) type of compounds based on two regioisomers of diketopyrrolopyrrole. Diketopyrrolo[3,4-c]pyrrole (DPP1), a well known electron acceptor moiety and its regioisomer diketopyrrolo[3,2-b]pyrrole (DPP2) are coupled with various electron donor groups containing fused ring system to obtain model compounds of D-A-D type of architecture. The donor groups include meta-benzodithiophene, ortho-benzodithiophene, carbazole, dithienopyrrole, dithienosilole and dithienothiophene. An analysis of their properties reveal that these compounds possess unique characteristics and advantages over each other. Density functional theory (DFT) calculations show that the DPP2-based compounds exhibit lower hole reorganization energy (λh) than the corresponding DPP1-based compounds, while the DPP1-based compounds have lower electron reorganization energy (λe) than the corresponding DPP2-based compounds, which is in line with the observed ionizational potential (IP) and electron affinity (EA) values. The calculated open circuit voltage (Voc) and the fill factor (FF) values of the DPP2-based compounds as donors with fullerene-like PC61BM as an acceptor are higher than the DPP1-based compounds as donors. Charge density difference (CDD) calculation shows DPP2 based compounds exhibit better intramolecular charge transfer (ICT) properties as compared to their DPP1 counterpart. The weaker electron-hole coherence may lead to easy exciton dissociation in case of DPP1-based compounds at donor/acceptor interface, which is also supported by their comparatively lower exciton binding energy as compared to DPP2 counterparts.

Investigating the Nucleation Kinetics of Calcium Carbonate Using a Zero-Water-Loss Microfluidic Chip

Density functional theory (DFT) calculations have been performed to investigate the electronic structure and photocatalytic activity of a hybrid Ag3PO4(111)/g-C3N4 structure. Due to Ag(d) and O(p) states forming the upper part of the valence band and C(p), N(p), and Ag(s) the lower part of the conduction band, the band gap of the hybrid material is reduced from 2.75 eV for Ag3PO4(111) and 3.13 eV for monolayer of g-C3N4 to about 2.52 eV, enhancing the photocatalytic activity of the Ag3PO4(111) surface and g-C3N4 sheet in the visible region. We have also investigated possible reaction pathways for photocatalytic CO2 reduction on the Ag3PO4(111)/g-C3N4 nanocomposite to determine the most favored adsorption geometries of reaction intermediates and the related reaction energies. For CO2 reduction, our findings demonstrate that the Ag3PO4(111)/g-C3N4 heterostructure thermodynamically exhibits a higher selectivity toward CH4 production than that of CH3OH. The CO2 reduction process takes place through either HCOOH* or HOCOH* as an intermediate species, where the highest exothermic reaction energy of −2.826 eV belongs to the hydrogenation of t-COOH* to HCOOH* and the lowest reaction energy of −0.182 eV for hydrogenations of CH2O* to CH2OH* and HCO* to c-HCOH*. Our results from charge density difference calculations of the Ag3PO4(111)/Ag/g-C3N4 revealed that the charge transfer between the Ag3PO4(111) slab and g-C3N4 monolayer occurs through mediation of atomic Ag, thus proposing a Z-scheme mechanism. Moreover, a smaller band gap energy of 0.73 eV is calculated for this ternary nanocomposite due to the midgap states of the atomic Ag at the interface. These results provide in depth understanding of the reaction mechanism in the reduction and conversion of CO2 to useful chemicals via an Ag3PO4 and g-C3N4-based nanocomposite photocatalyst under visible light.

RETRACTED: Adsorption of gas molecules on the defective stanene nanosheets with single vacancy: A DFT study

Abstract Using the first-principles calculations, we have systematically examined the adsorption of gas molecules on the pristine and vacancy defective stanene monolayers. The adsorption of gas molecules on the defective monolayers is much stronger than that on the perfect ones, indicating the suitability of defective stanene nanosheets for adsorption processes. The large adsorption energies for SO2 and SO3 adsorbed complexes indicate the strong reactivity of stanene systems with adsorbed gas molecules, leading to the formation of multiple contacting points at the interface. The formation energies for the defective stanene systems were calculated. Our results indicated that the single vacancy defective stanene monolayers are thermodynamically stable, and can be used as effective gas sensors. The charge density difference calculations indicate that the electronic densities were largely accumulated between the atoms interacting with each other. This strong chemical interaction was also evidenced by the large overlaps of the density of states between the interacting atoms. The band structure calculations reveal the semiconductor features for defective stanene monolayers with adsorbed gas molecules. Our obtained results would be useful to search for promising gas sensor devices based on vacancy defective stanene monolayers.

Adsorption of thiophene and SOx molecules on Cr-doped and Ti-doped graphene nanosheets: a DFT study

Density functional theory calculations were carried out to investigate the structural and electronic properties of Cr- and Ti-embedded graphene monolayers. Sequentially, the adsorption of some gas molecules and thiophene molecule on these modified two-dimensional materials were examined in detail. The results suggest that the adsorption of all gas molecules on Cr- and Ti-embedded graphene monolayers is more energetically favorable than that on the pristine ones. Band structure calculations indicate that Cr-embedded graphene monolayer exhibits metallic behavior, while Ti-embedded one acts as a semiconductor. All the studied gas molecules were strongly adsorbed on the transition metal site of doped monolayer with the formation of covalent bonds. These strong chemical adsorptions were confirmed by the projected density of states and charge density difference plots. Charge density difference calculations also show that the electronic densities were mainly accumulated on the adsorbed gas molecules. The results presented in this study shed light on the prospective capability of transition metal decorated graphene nanosheets in sensing devices.

Reversible lithium storage capacity on carbon nitride by electric field

Abstract Graphitic carbon nitride (g-C3N4) has attracted enormous interest because of its prominent photocatalytic performance. Due to the planar π conjugation structure which should provide good binding energy for adsorption of metal atoms including lithium (Li) and sodium (Na), g-C3N4 also possesses great application potential in ion batteries. Here, first-principles calculations are performed to investigate its application in lithium ion batteries (LIBs), focusing on the electric field effect on the Li storage. Our results revealed that Li adsorbed C3N4 (Li–C3N4) exhibits good modulation of its Li binding energy by applying external vertical electric field. The Bader charge analysis and charge density difference calculations provide a deep insight into the tunable Li adsorption to C3N4 sheets. Our theoretical results suggest that C3N4 is a suitable anode material for LIBs.

Mechanism of Photocatalytic Reduction of CO2 by Ag3PO4(111)/g-C3N4 Nanocomposite: A First-Principles Study

Density functional theory (DFT) calculations have been performed to investigate the electronic structure and photocatalytic activity of a hybrid Ag3PO4(111)/g-C3N4 structure. Due to Ag(d) and O(p) states forming the upper part of the valence band and C(p), N(p) and Ag(s) the lower part of the conduction band, the band gap of the hybrid material is reduced from 2.75 eV for Ag3PO4(111) and 3.13 eV for monolayer of g-C3N4 to about 2.52 eV, enhancing the photocatalytic activity of the Ag3PO4(111) surface and g-C3N4 sheet in the visible region. We have also investigated possible reaction pathways for photocatalytic CO2 reduction on the Ag3PO4(111)/g-C3N4 nanocomposite to determine the most favored adsorption geometries of reaction intermediates and the related reaction energies. For CO2 reduction, our findings demonstrate that the Ag3PO4(111)/g-C3N4 heterostructure thermodynamically exhibits a higher selectivity towards CH4 production than that of CH3OH. The CO2 reduction process takes place through either HCOOH* or HOCOH* as an intermediate species, where the highest exothermic reaction energy of -2.826 eV belongs to the hydrogenation of t-COOH* to HCOOH* and the lowest reaction energy of -0.182 eV for hydrogenations of CH2O* to CH2OH* and HCO* to c-HCOH*. Our results from charge density difference calculations of the Ag3PO4(111)/Ag/g-C3N4 revealed that the charge transfer between the Ag3PO4(111) slab and g-C3N4 monolayer occurs through mediation of atomic Ag, thus proposing a Z-scheme mechanism. Moreover, a smaller band gap energy of 0.73 eV is calculated for this ternary nanocomposite due to the mid-gap states of the atomic Ag at the interface. These results provide in depth understanding of the reaction mechanism in the reduction and conversion of CO2 to useful chemicals via an Ag3PO4 and g-C3N4-based nanocomposite photocatalyst under visible light.

Adsorption of CO and NO molecules on Al, P and Si embedded MoS2 nanosheets investigated by DFT calculations

Using density functional theory (DFT), we presented a theoretical investigation of CO and NO gas molecules adsorption on the Al-doped, P-doped and Si-doped MoS2 monolayers. Our main focus is on the interactions between the dopants (Al, P and Si) and gas molecules. The properties of the adsorption system were analyzed in view of the density of states, electron density distribution, charge density differences and electronic band structures. Various orientations of CO and NO molecules were considered on the MoS2 monolayer to search for the most stable configurations. The results suggest that the adsorption of gas molecules on the doped MoS2 monolayers is more favorable in energy than that on the pristine monolayers. This means that the interaction between doped MoS2 and gas molecules is stronger than that between pristine MoS2 and gas molecules. Our calculations show shorter adsorption distance and higher adsorption energy for Al-doped and Si-doped monolayers than the P-doped and pristine ones. Charge density difference calculations show the charge accumulation between the interacting atoms, suggesting the formation of covalent bonds, as evidenced by the projected density of states of the interacting atoms. Our results confirm that Al-doped and Si-doped MoS2 can be used as efficient and promising sensor materials for CO and NO detection in the environment.

Theoretical Investigation of The interaction Between Noble Metals (Ag, Au, Pd, Pt) and Stanene Nanosheets: A DFT Study

Adsorption of noble metals (Ag, Au, Pd and Pt) on the pristine stanene monolayers was investigated using the density functional theory calculations. Three different adsorption positions of noble metals on the stanene monolayer were considered, namely the top, valley and hollow sites. The structural stability of the metal adsorbed systems were discussed in term of adsorption energies. The results predict that the adsorption of noble metals on the hollow site of the stanene hexagon is more energetically favorable than that on the top and valley sites. Charge density difference calculations show that the charges were mainly accumulated over the adsorbed noble metals. The significant overlaps between the PDOS spectra of the noble metal and tin atoms indicate the formation of chemical bonds between them. Charge analysis based on Hirshfeld net atomic charges reveals a noticeable charge transfer from the stanene sheet to the adsorbed noble metals. Furthermore, the band structure calculations confirm that Ag and Au adsorbed stanene systems exhibit metallic behavior, whereas Pd and Pt adsorbed ones show semiconductor characteristics. The inclusion of SOC effect does not change the electronic phase of the systems, while the band gap gets narrower. The results confirm that noble metal embedded stanene monolayer can be used as effective and potential candidates for application in next-generation nanoelectronic devices.

Modulation of the electronic properties of pristine and AlP-codoped stanene monolayers by the adsorption of CH2O and CH4 molecules: a DFT study

The adsorption of formaldehyde (CH2O) and methane (CH4) on the pristine and AlP-codoped stanene monolayers were investigated using the density functional theory calculations in order to search for potential sensors for detection of CH2O and CH4 molecules. The effects of CH2O and CH4 adsorption on the structural and electronic properties of stanene monolayers were systematically studied. The results indicated that both CH2O and CH4 molecules were physisorbed on the stanene sheets with small adsorption energy and large adsorption distance. The adsorption of CH2O and CH4 on the AlP-codoped stanene is more energetically favorable than that on the pristine one. Band structure calculations indicate that CH2O and CH4 adsorbed pristine and AlP-codoped stanene show semiconductor characteristics. The charge density difference calculations represent the significant charge accumulation on the adsorbed gas molecules. The considerable changes in the electronic properties of stanene induced by gas adsorption suggest the potential application of these group-IV buckled nanomaterials for CH2O and CH4 detection.

Adsorption of phenol, hydrazine and thiophene on stanene monolayers: A computational investigation

The adsorption of phenol, hydrazine and thiophene molecules on the stanene monolayers were investigated using the density functional theory calculations. Various adsorption positions of molecules on the stanene monolayers were tested. The properties of the adsorption systems were investigated in terms of adsorption distance, adsorption energy, band structures, molecular orbitals, charge density difference (CDD) and projected density of states (PDOS). Adsorption energy results indicate that the adsorption of phenol, hydrazine and thiophene molecules on the stanene is energetically favorable. Phenol and thiophene molecules show a weak physisorption on the stanene monolayers due to the lack of covalent bond at the interface region, whereas hydrazine exhibits chemisorption on the stanene sheet. The adsorption of phenol, hydrazine and thiophene molecules induces a narrow band gap at the Fermi level of stanene, leading to the semiconductor property of the combined system (stanene + adsorbate). The adsorption of hydrazine on the surface makes a more significant change on the electronic properties of stanene than that of phenol and thiophene. The large PDOS overlaps between the PDOS spectra of the tin and nitrogen atoms indicate the formation of chemical bonds between these atoms. The charge density difference calculations represent charge accumulation on the adsorbed molecules.

Adsorption of O3, SO2 and SO3 gas molecules on MoS2 monolayers: A computational investigation

Owing to the wide surface area, two-dimensional materials such as MoS2 are being used for chemical sensing of harmful gas molecules, which reduce the concentration of these pollutants to an environmentally acceptable value. Using density functional theory calculations, the adsorptions of SO2, SO3 and O3 gas molecules on MoS2 monolayers were studied in terms of adsorption energy, charge transfer, band structures, and charge density differences. The results suggest that the adsorption of gas molecules on the MoS2 is energetically favorable, which gives rise to the most stable configurations. Besides, the gas molecules were physisorbed on the monolayer surface due to the weak interaction between them and MoS2. The OO and SO bonds of the adsorbed gas molecules were elongated after the adsorption process. This elongation of bond lengths is mostly attributed to the transfer of electronic density from the old bonds to the newly formed bonds between the molecules and MoS2. The band structure calculations indicate that the electronic properties of the MoS2 monolayers are altered upon the adsorption of gas molecules. Furthermore, the charge density difference calculations reveal the charge accumulation on the adsorbed molecules, which indicate the acceptor property of these gas molecules.

Structural and electronic properties of group-IV tin nanotubes and their effects on the adsorption of SO2 molecules: Insights from DFT computations

The structural and electronic properties of pristine and SO2 adsorbed buckled tin nanotubes were investigated using density functional theory calculations. The effects of SO2 gas adsorption on the electronic structure of the nanotubes were analyzed in detail. SO2 molecule was initially positioned on the armchair and zigzag stanene based nanotubes with orientations through both interacting sulfur and oxygen sites. The results suggest that the considered armchair nanotubes have direct bandgaps at the K point, indicating the semiconductor characteristics of these nanotubes. Thus, these nanotubes are efficient candidates for gas sensing applications. Moreover, the considered (9, 0) and (10, 0) zigzag nanotubes also exhibit semiconductor behavior. Among the armchair nanotubes, the highest (most negative) adsorption energy belongs to (8, 8) armchair nanotube, which indicates that SO2 interaction with (8, 8) nanotube is energetically most favorable. The adsorption energy slightly increases with increasing the nanotube diameter. Besides, the adsorption of the SO2 molecule on the nanotube surface through its oxygen atoms is more favorable in energy than that through its central sulfur atom. The projected density of states of the interacting tin and oxygen atoms show the formation of chemical bonds between these atoms, as evidenced by the accumulation of electronic density at the middle of the newly formed bonds. Based on charge density difference calculations, we found the charge accumulation on the adsorbed SO2 molecule, which represents that SO2 acts as a charge acceptor.

First-principles hydrogen adsorption properties of Li-decorated ThMoB4-type graphene

The hydrogen storage (1–10H2) properties of single- and double-side lithium decorated ThMoB4-type graphene (Li/ThMoB4C) are systematically investigated by density functional first-principles calculations within Dmol3 package. After well-converged geometry optimizations, it is found that the binding energy of Li adatom is higher enough, and there is no adatom clustering. The average adsorption energies of 1–6 H2 deviate in 0.20–0.27 eV/H2 range, which is providing a convenient physical adsorption-desorption cycle. A detailed examination of the binding mechanism between the constituents of the H2 adsorbed Li-decorated systems is presented by density of states, Mulliken charge analysis, electron density and density difference calculations. For further decoration and adsorption with 12Li adatom and 72H2 molecules, the computation yields a high gravimetric density of 14.5 wt % with the acceptable adsorption energy. In this way, it is concluded that Li/ThMoB4 system can be considered as a promising hydrogen storage medium.

Insight into the optoelectronic properties of designed solar cells efficient tetrahydroquinoline dye-sensitizers on TiO2(101) surface: first principles approach

Seven ‘lead’ dye-sensitizers from Tetrahydroquinoline (THQ) family were proposed and designed based on the structural attributes via quantitative-structure property relationship (QSPR) modeling. They were screened rationally through different computational approaches to explore their potential applications as photosensitizers for dye-sensitized solar cells (DSSCs). Compelling photophysical properties such as electron injection driving force, electron injection time, and dye regeneration were studied for the isolated dyes under the DFT and TD-DFT frameworks. Index of spatial extent (S, D, and ∆q), the strength of charge transfer and separation along with the charge transfer process is explored. First principle approach including van der Waals density functional calculation of dye@TiO2 interface indicates that all of the designed dyes have optimal interfacial behavior. Bader charge analysis, partial density of state (PDOS), charge density and electrostatic potential difference calculation confirms that THQ7 and THQ9 are the most efficient dye-sensitizers. The other five designed dyes also possess the required properties to emerge as effective dye-sensitizers potentially better than those already utilized.