scholarly journals Adsorption of Cr(OH)n(3−n)+ (n = 1–3) on Illite (001) and (010) Surfaces: A DFT Study

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2048
Author(s):  
Jia Du ◽  
Leilei Fan ◽  
Qinghe Wang ◽  
Fanfei Min
Keyword(s):  
Electrostatic Interactions ◽  
Density Functional ◽  
Covalent Bond ◽  
Hydroxyl Groups ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Highly Active ◽  
Adsorption Energies ◽  
State Densities ◽  
Covalent Interactions

The development of clay adsorption materials with high Cr(III) removal capacities requires an understanding of the adsorption mechanism at the atomic level. Herein, the mechanisms for the adsorption of Cr(OH)2+, Cr(OH)2+, and Cr(OH)3 on the (001) and (010) surfaces of illite were studied by analyzing the adsorption energies, adsorption configurations, charges, and state densities using density functional theory (DFT). The adsorption energies on the illite (010) and (001) surfaces decrease in the order: Cr(OH)2+ > Cr(OH)2+ > Cr(OH)3. In addition, the energies associated with adsorption on the (010) surface are greater than those on the (001) surface. Further, the hydrolysates are highly active and can provide adsorption sites for desorption agents. The silica (Si–O) ring on the illite (001) surface can capture Cr(OH)n(3−n)+ (n = 1–3). In addition, both Cr(OH)2+ and Cr(OH)2+ form one covalent bond between Cr and surface OS1 (Cr–OS1), whereas the hydroxyl groups of Cr(OH)3 form three hydrogen bonds with surface oxygens. However, increasing the number of hydroxyl groups in Cr(OH)n(3−n)+ weakens both the covalent and electrostatic interactions between the adsorbate and the (001) surface. In contrast, the Cr in all hydrolysates can form two covalent Cr–OSn (n = 1–2) bonds to the oxygens on the illite (010) surface, in which Cr s and O p orbitals contribute to the bonding process. However, covalent interactions between the cation and the (010) surface are weakened as the number of hydroxyl groups in Cr(OH)n(3−n)+ increases. These results suggest that the illite interlayer can be stripped to expose Si–O rings, thereby increasing the number of adsorption sites. Furthermore, regulating the generated Cr(III) hydrolysate can increase or weaken adsorption on the illite surface. Based on these findings, conditions can be determined for improving the adsorption capacities and optimizing the regeneration performance of clay mineral materials.

scholarly journals Density Functional Theory Study Of The Interaction Of Hydroxyl Groups With Iron Surface

2015 ◽  
Vol 60 (2) ◽  
pp. 931-933 ◽  
Author(s):  
N. Nunomura ◽  
S. Sunada
Keyword(s):  
Density Functional Theory ◽  
Iron Atom ◽  
Density Functional ◽  
Lone Pair ◽  
Hydroxyl Groups ◽  
Electronic Interaction ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Surface Iron ◽  
Adsorption Energies

AbstractThe electronic interaction of hydroxyl groups with Fe(100) surface is modelled using a density functional theory (DFT) approach. The adsorption energies and structures of possible adsorption sites are calculated. According to our calculations of the adsorption energies, the interaction between oxygen atom of OH species and surface iron atom is shown to be strong. It is likely to be due to the interaction of the lone-pair electrons of oxygen and the 3dorbital electrons of iron atom. At low coverage (0.25ML), the most favorable adsorption sites are found to be two-fold bridge sites, and the orientation of the O-H bond is tilted to the surface normal. Further, the adsorption energy is found to be decreasing with the increasing OH group coverage.

ADSORPTION SITES OF THE PRODUCTS OF GeH4 ON ASYMMETRIC Si(100)(2×1) SURFACE

2004 ◽  
Vol 18 (08) ◽  
pp. 1191-1202
Author(s):  
ŞENAY KATıRCıOĞLU
Keyword(s):  
Density Functional ◽  
Geometry Optimization ◽  
Density Functional Theory Method ◽  
Adsorption Model ◽  
Functional Theory ◽  
Adsorption Models ◽  
Adsorption Sites ◽  
Asymmetric Dimer ◽  
Adsorption Energies ◽  
Relative Adsorption

The decomposition of GeH 4 on Si (100)(2×1) was investigated on different adsorption models of fragments using density functional theory method. The most probable adsorption model of fragments corresponding to the growth steps of SiGe film has been obtained by geometry optimization and single value total energy calculations. The relative adsorption energies of GeH 3, GeH 2 and GeH have been found to be -5.6, -5.1, and -4.5 eV for their most probable adsorption models respectively. It has been found that, the asymmetric dimer bond rows of Ge on Si (100) surface can be constructed by following the adsorption models corresponding to the relative adsorption energies of GeH 3, GeH 2 and GeH .

scholarly journals The influence of the grafted aryl groups on the solvation properties of the graphyne and graphdiyne - a MD study

2019 ◽  
Vol 17 (1) ◽  
pp. 703-710 ◽  
Author(s):  
Avni Berisha
Keyword(s):  
Molecular Dynamics ◽  
Aqueous Solution ◽  
Density Functional Theory ◽  
Density Functional ◽  
Phenyl Group ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Water As Solvent ◽  
Non Covalent Interactions ◽  
Covalent Interactions

AbstractThe mechanism of the adsorption and grafting of diazonium cations onto the surface of graphyne and graphdiyne was investigated using Density Functional Theory (DFT). The adsorption energy (both in vacuum and water as solvent) of the phenyl diazonium cation was evaluated at three different positions of the graphyne and graphdiyne surface. Moreover, the lowest energy adsorption sites were used to calculate and plot Non-covalent Interactions (NCI). The Bond Dissociation Energy (BDE) results (up to 66 kcal/mol) for the scission of the phenyl group support the remarkable stability of the grafted layer. As both of these materials are non-dispersible in aqueous solution, in this work through the use of Molecular Mechanics (MM) and Molecular Dynamics (MD) we explored also the effect of the grafted substituted aryl groups derived from aryldiazonium salts onto the solvation properties of these materials.

Theoretical Studies of the Atomic and Electronic Structure of Mercury/Aluminium Oxide Interface

2011 ◽  
Vol 255-260 ◽  
pp. 2972-2976 ◽  
Author(s):  
Ping He ◽  
Jiang Wu ◽  
Xiu Min Jiang ◽  
Nai Chao Chen
Keyword(s):  
Charge Density ◽  
Density Functional ◽  
Covalent Bond ◽  
Partial Density ◽  
Oxide Interface ◽  
Functional Theory ◽  
Adsorption Sites ◽  
Interacting Electrons ◽  
Strong Covalent Bond ◽  
Evolution Tendency

Density-functional theory (DFT) theory is conducted for the structural and electronic features at the Hg/Al2O3 interface by the analysis of optimal structural geometry, partial density of states (PDOS) and difference charge density. The two adsorption sites of on-top and hollow locations according to the symmetry is adopted to construct the associated interfacial models between Hg atom and free surface. The calculated studies show that the oxygen atoms near Hg atom in the Al2O3 surface, for both on-top and hollow sites, have the gathering effect by shifting toward Hg atom. But their interacting electrons at the interface exhibit different statues in terms of the PDOS analysis that there have no evolution tendency to form the bond between associated O and Hg atoms at the on-top site; and the occurrence of Hg-5d and O-2p overlapping orbitals reveals the strong covalent bond existed at the interface. The PDOS curves show that Al atom in the surface is not liable to contribute to the formation of corresponding bonds by mixing its electrons with Hg atom. Meanwhile, the calculated results derived from difference charge density are in good agreement with the PDOS analysis. The calculated results support some advanced atomic investigation on design a new sorbent refined from fly gas, especially improving the mercury removal from the flue gas.

Multistep reactions of water with small Pdn clusters: A first principles study

2015 ◽  
Vol 14 (03) ◽  
pp. 1550017 ◽  
Author(s):  
Yanhua Liang ◽  
Li Ma ◽  
Jianguang Wang ◽  
Guanghou Wang
Keyword(s):  
Water Molecule ◽  
Density Functional ◽  
Dissociative Chemisorption ◽  
Weakly Bound ◽  
Functional Theory ◽  
Site Specific ◽  
Molecular Adsorbates ◽  
Adsorption Sites ◽  
Adsorption Energies ◽  
Pd Clusters

Multistep dissociative chemisorption reactions of water with Pd 4 and Pd 7 clusters were studied using density functional theory. The adsorption energies and referred adsorption sites from water molecule ( H 2 O ) to partially dissociative ( H 2+ O and OH + H ), then to fully dissociative ( O + H + H ) configurations are carefully determined. It is found that the adsorption energies of three dissociative reactions are 5–6 times larger than that of water molecule. Atop sites of Pd 4 and Pd 7 clusters are found to be the most stable sites for the adsorbed H 2 O molecule. For the coadsorption cases of partially and fully dissociated products, H 2 and OH molecules preferably tend to bind at the low coordination (atop or bridge) sites, and O and H atoms prefer to adsorb on the high coordination (hollow) sites. It is also found that the most favorable adsorption sites for the molecular adsorbates ( H 2 O , H 2 and OH ) are adjacent to the Pd atoms with the largest site-specific polarizabilities. Therefore, site-specific polarizability is a good predictor of the favorable adsorption sites for the weakly bound molecules. The different directions of charge transfer between the Pd clusters and the adsorbate(s) is observed. Furthermore, the processes of the adsorption, dissociation, and the dissociative products diffusion of H 2 O are analyzed.

Intrinsic Stacking Interactions of Natural and Artificial Nucleobases

2019 ◽  
Author(s):  
Drew P. Harding ◽  
Laura J. Kingsley ◽  
Glen Spraggon ◽  
Steven Wheeler
Keyword(s):  
Gas Phase ◽  
Electrostatic Interactions ◽  
Density Functional ◽  
Molecular Descriptors ◽  
Stacking Interactions ◽  
Interaction Energies ◽  
Functional Theory ◽  
Binding Partner ◽  
Heavy Atoms ◽  
Wide Range

The intrinsic (gas-phase) stacking energies of natural and artificial nucleobases were explored using density functional theory (DFT) and correlated ab initio methods. Ranking the stacking strength of natural nucleobase dimers revealed a preference in binding partner similar to that seen from experiments, namely G > C > A > T > U. Decomposition of these interaction energies using symmetry-adapted perturbation theory (SAPT) showed that these dispersion dominated interactions are modulated by electrostatics. Artificial nucleobases showed a similar stacking preference for natural nucleobases and were also modulated by electrostatic interactions. A robust predictive multivariate model was developed that quantitively predicts the maximum stacking interaction between natural and a wide range of artificial nucleobases using molecular descriptors based on computed electrostatic potentials (ESPs) and the number of heavy atoms. This model should find utility in designing artificial nucleobase analogs that exhibit stacking interactions comparable to those of natural nucleobases. Further analysis of the descriptors in this model unveil the origin of superior stacking abilities of certain nucleobases, including cytosine and guanine.

scholarly journals Role of Chemistry and Crystal Structure on the Electronic Defect States in Cs-Based Halide Perovskites

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1032
Author(s):  
Anirban Naskar ◽  
Rabi Khanal ◽  
Samrat Choudhury
Keyword(s):  
Crystal Structure ◽  
Density Functional ◽  
Covalent Bond ◽  
Density Functional Theory Calculations ◽  
Antisite Defect ◽  
Defect States ◽  
Functional Theory ◽  
Electronic Defect ◽  
Constituent Elements

The electronic structure of a series perovskites ABX3 (A = Cs; B = Ca, Sr, and Ba; X = F, Cl, Br, and I) in the presence and absence of antisite defect XB were systematically investigated based on density-functional-theory calculations. Both cubic and orthorhombic perovskites were considered. It was observed that for certain perovskite compositions and crystal structure, presence of antisite point defect leads to the formation of electronic defect state(s) within the band gap. We showed that both the type of electronic defect states and their individual energy level location within the bandgap can be predicted based on easily available intrinsic properties of the constituent elements, such as the bond-dissociation energy of the B–X and X–X bond, the X–X covalent bond length, and the atomic size of halide (X) as well as structural characteristic such as B–X–B bond angle. Overall, this work provides a science-based generic principle to design the electronic states within the band structure in Cs-based perovskites in presence of point defects such as antisite defect.

scholarly journals Weak Interactions in Cocrystals of Isoniazid with Glycolic and Mandelic Acids

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 328
Author(s):  
Raquel Álvarez-Vidaurre ◽  
Alfonso Castiñeiras ◽  
Antonio Frontera ◽  
Isabel García-Santos ◽  
Diego M. Gil ◽  
...  
Keyword(s):  
Density Functional ◽  
Glycolic Acid ◽  
Weak Interactions ◽  
Three Dimensional ◽  
Functional Theory ◽  
Molecular Systems ◽  
X Ray Crystallography ◽  
Hydroxycarboxylic Acids ◽  
Non Covalent Interactions ◽  
Covalent Interactions

This work deals with the preparation of pyridine-3-carbohydrazide (isoniazid, inh) cocrystals with two α-hydroxycarboxylic acids. The interaction of glycolic acid (H2ga) or d,l-mandelic acid (H2ma) resulted in the formation of cocrystals or salts of composition (inh)·(H2ga) (1) and [Hinh]+[Hma]–·(H2ma) (2) when reacted with isoniazid. An N′-(propan-2-ylidene)isonicotinic hydrazide hemihydrate, (pinh)·1/2(H2O) (3), was also prepared by condensation of isoniazid with acetone in the presence of glycolic acid. These prepared compounds were well characterized by elemental analysis, and spectroscopic methods, and their three-dimensional molecular structure was determined by single crystal X-ray crystallography. Hydrogen bonds involving the carboxylic acid occur consistently with the pyridine ring N atom of the isoniazid and its derivatives. The remaining hydrogen-bonding sites on the isoniazid backbone vary based on the steric influences of the derivative group. These are contrasted in each of the molecular systems. Finally, Hirshfeld surface analysis and Density-functional theory (DFT) calculations (including NCIplot and QTAIM analyses) have been performed to further characterize and rationalize the non-covalent interactions.

scholarly journals 1,3,5-Triaza-7-Phosphaadamantane (PTA) as a 31P NMR Probe for Organometallic Transition Metal Complexes in Solution

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1390 ◽  
Author(s):  
Ilya G. Shenderovich
Keyword(s):  
Chemical Shift ◽  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Density Functional ◽  
Molecular Structures ◽  
Basis Sets ◽  
Functional Theory ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Due to the rigid structure of 1,3,5-triaza-7-phosphaadamantane (PTA), its 31P chemical shift solely depends on non-covalent interactions in which the molecule is involved. The maximum range of change caused by the most common of these, hydrogen bonding, is only 6 ppm, because the active site is one of the PTA nitrogen atoms. In contrast, when the PTA phosphorus atom is coordinated to a metal, the range of change exceeds 100 ppm. This feature can be used to support or reject specific structural models of organometallic transition metal complexes in solution by comparing the experimental and Density Functional Theory (DFT) calculated values of this 31P chemical shift. This approach has been tested on a variety of the metals of groups 8–12 and molecular structures. General recommendations for appropriate basis sets are reported.

scholarly journals Atoms in Highly Symmetric Environments: H in Rhodium and Cobalt Cages, H in an Octahedral Hole in MgO, and Metal Atoms Ca-Zn in C20 Fullerenes

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1281
Author(s):  
Zikri Altun ◽  
Erdi Ata Bleda ◽  
Carl Trindle
Keyword(s):  
Density Functional Theory ◽  
Quantum Theory ◽  
Coordination Number ◽  
Electronic Structures ◽  
Density Functional ◽  
Functional Theory ◽  
Metal Atoms ◽  
Tetragonal Pyramidal ◽  
Non Covalent Interactions ◽  
Covalent Interactions

An atom trapped in a crystal vacancy, a metal cage, or a fullerene might have many immediate neighbors. Then, the familiar concept of valency or even coordination number seems inadequate to describe the environment of that atom. This difficulty in terminology is illustrated here by four systems: H atoms in tetragonal-pyramidal rhodium cages, H atom in an octahedral cobalt cage, H atom in a MgO octahedral hole, and metal atoms in C20 fullerenes. Density functional theory defines structure and energetics for the systems. Interactions of the atom with its container are characterized by the quantum theory of atoms in molecules (QTAIM) and the theory of non-covalent interactions (NCI). We establish that H atoms in H2Rh13(CO)243− trianion cannot be considered pentavalent, H atom in HCo6(CO)151− anion cannot be considered hexavalent, and H atom in MgO cannot be considered hexavalent. Instead, one should consider the H atom to be set in an environmental field defined by its 5, 6, and 6 neighbors; with interactions described by QTAIM. This point is further illustrated by the electronic structures and QTAIM parameters of M@C20, M=Ca to Zn. The analysis describes the systematic deformation and restoration of the symmetric fullerene in that series.

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