Addition Reactivity of C_（36） Cage Controlled by the Curvature and the Electronic Factors：A DFT Study

The molecular geometries and electronic structures of the fullerene derivatives C36(OH)n(n = 1～2) have been investigated on the basis of density functional theory calculation at the B3LYP/6-31++G* level.The geometry optimization results indicate that the location of C2 atom is the most active site in the three potential adding patterns,and the C1 or C2 site has a larger binding energy than C3 for the addition reactions of C36(D6h) cage and OH radicals resulting from the larger curvature.The electronic structure calculation results disclose that the C2 site has larger electronic population in HOMO and larger spin density,and the addition reaction on the C2 site need overcome a lesser energy gap than that on the C1 or C3 site.Thus,the addition is controlled jointly by the curvature and the electronic factors.Besides,when two hydroxyls are added to the C36 surface,the C2 sites are also the most active locations.The most stable addition adduct of C36(OH)2 is the isomer which holds Ci symmetry,and the spin multiplicity seriously affects the stabilities of the adducts.     

Study of Two Puzzled Questions on the Fullerene C_（70）：A First-principles Study

The cycloaddition reactions of NH to different bonds on C70 have been studied by the first-principles calculations.The results indicate that the reactivity of cycloaddition reactions is determined by the directional curvature,KD,and the larger binding energy of Eb on the bond C5-C'5 can be ascribed to the unique bond which can be treated as the shortest bond of(5.5)-SWCNT in the four [6,6] ring fusion bonds.This work also discloses that the energy gap of different spin states is decided by the electronic density,and that of the frontier obitals for the bond C5-C'5 is larger than the value for the C4-C'4 bond.Furthermore,the transition state investigation of the two bond addition reactions provides a reaction barrier of 11.10 kcal/mol for the NH cycloaddition to the C5-C'5 bond;whereas,the addition reaction on C4-C'4 is a spontaneous pathway.Herein,the dynamics effect illustrates the [2+1] cycloaddition reaction on the equatorial C5-C'5 bond to be unfavorable.     

HCN Adsorption on the Fe(100), Fe(111) and Fe(110) Surfaces: a Density Functional Theory Study

Twenty kinds of adsorptions of HCN on the Fe(100), Fe(111) and Fe(110) surfaces at the 1/4 monolayer coverage are found using the density functional theory. For Fe(100), the adsorption energy of the most stable configuration where the HCN locates at the fourfold site with the C-N bonded to four Fe atoms is 1.928 eV. The most favored adsorption structure for HCN on Fe(111) is f-η3(N)-h-η3(C), in which the C-N bond is almost parallel to the surface, and the adsorption energy is 1.347 eV. On Fe(110), the adsorption energy in the most stable configuration in which HCN locates at the two long-bridge sites is 1.777 eV. The adsorption energy of the parallel orientation for HCN is larger than that of the perpendicular configuration. The binding mechanism of HCN on the Fe(100), Fe(111) and Fe(110) surfaces is also analyzed by Mulliken charge population and the density of states in HCN. The result indicates that the configurations in which the adsorbed HCN becomes the non-linear are beneficial to the formation of the addition reaction for hydrogen. The nature that the introduction of Fe into the catalyst could increase the catalytic activity of the bimetallic catalyst in the addition reaction of hydrogen for nitriles is revealed.     

Adsorption of cyclohexene and its dehydrogenation intermediates on nAu/Pt(100)(n＝0,1,2) surfaces:A DFT study

Adsorption of cyclohexene and its dehydrogenation intermediates on the nAu/Pt(100) (n = 0, 1, 2 means clean Pt, one monolayer and two layers of Au covered Pt surfaces, respectively.) has been investigated by self-consistent (GGA-PW91) density functional theory combined with periodic slab model. It is found that on the clean platinum, there are two kinds of favorable adsorption sites, i.e., hollow sites and bridge sites, and the adsorption energy at the hollow site is larger than that at the bridge site. However, on the Au/Pt and 2Au/Pt surfaces, there are three kinds of adsorption sites, and the adsorption energies are alike at both the bridge site and the top site. The magnitude order of the adsorption energies is as follows: clean Pt > Au/Pt > 2Au/Pt. The configurations of cyclohexene molecule have been distorted a little during the geometry optimizations. The lengths of C–M (M = Pt or Au, on the top layer of the slab) bonds are closely related to the corresponding adsorption energies.     

MECHANISM OF METHANOL DECOMPOSITION ON CLEAN AND OXYGEN-MODIFIED Fe,Cu SURFACES:BOND-ORDER CONSERVATION APPROACH

Bond-order conservation-Morse potential (BOC-MP) approach hasbeen used to study the mechanism of methanol decomposition on the clean andoxygen-modified Fe(100), Cu (100) surfaces. On the clean Cu (100) surfacemethanol was adsorbed in molecular forms and desorbed without dissociation,but on the clean Fe(100) surface it decomposed via a methoxy (CH_3O) inter-mediate into carbon monoxide (CO) and hydrogen (H_2) mainly, or into methyl(CH_3) and hydroxyl (OH) species directly. The thermal stability of methoxyincreased in the presence of pre-adsorbed oxygen(O_3). Hollow site O_3 poisonedthe decomposition of methanol, but non-hollow site O_3 promoted the decomposi-tion of methanol into the methoxy, which decomposed and selectively led to theformation of formaldehyde (H_2CO) on oxygen-modified Cu surfaces. The for-mation of formaldehyde via a disproportionation reaction of methoxy is also dis-cussed.     

Decomposition of methylamine on Mo(100) surface: A DFT study

The initial decomposition of methylamine on Mo(100) surface has been investigated by self-consistent (GGA-PW91) density functional theory combined with periodic slab model. The adsorption energies of possible species and the activation energies for possible elementary reactions involved are obtained in the present work. Our results indicate that the barriers decreased with the order of C-N>N-H>C-H. In addition, metastable adsorption of the abstracted hydrogen atom on the hollow site in the final state is also considered for the N-H and C-H bond breaking. For the C-H bond cleavage, the reaction barrier that the abstracted hydrogen located on the hollow site in the final state is lower than that on the bridge site. However, for the N H bond breaking, the barriers are alike for the abstracted hydrogen on both hollow and bridge sites in the final state.     

A DFT Study of Alkenes and Alkynes Reacting with H-GaN （0001） Surface

The addition reactions of alkenes and alkynes to the H-terminated GaN （0001） surface with a Ga dangling-bond have been studied employing periodic density functional theory （PDFT） calculations. Detailed information on the reaction pathways of these alkenes and alkynes with H-GaN （0001） surface is provided, which indicates that the reactions contain two steps separated by the metastable intermediates： elementary addition reaction and H-abstraction process. From the energy curves, the reactions are clearly viable in the cases of ethene, styrene and phenylacetylene; while for ethyne, the H-abstraction barrier is higher than the desorption barrier of the intermediate, so the adsorbed C2H2 in intermediate is more likely to be desorbed back into the gas phase than to form a stable adsorbed species. Furthermore, it is obvious that for either alkenes or alkynes, the systems substituted by phenyl have more stable intermediates because π conjugation could improve their stabilities.     

High-throughput calculation-based rational design of Fe-doped MoS2 nanosheets for electrocatalytic p H-universal overall water splitting

Electrocatalytic water splitting is crucial for H₂ generation via hydrogen evolution reaction(HER) but subject to the sluggish dynamics of oxygen evolution reaction(OER).In this work,single Fe atomdoped MoS₂ nanosheets(S_Fe-DMNs) were prepared based on the high-throughput density functional theory(DFT) calculation screening.Due to the synergistic effect between Fe atom and MoS₂ and optimized intermediate binding energy,the S_Fe-DMNs could deli...     

A DFT Study of Thiophene Adsorption on the Rh（111） Surfaces

Thiophene adsorption on the Rh(111) surfaces has been investigated by density functional theory.The results show that the adsorption at the hollow and bridge sites is the most stable.The molecular plane of the thiophene ring is distorted,the C=C bond is stretched to 1.448  and the C-C bond is shortened to 1.390.The C-H bonds tilt 22～42oaway from the surface.The calculated adsorption geometries are in reasonable agreement with population analysis and density of states.The thiophene molecule obtains 0.74 electrons,reflecting the interaction between the lone pair of sulfur and the d-orbitals of metal.The reaction paths and transition states for desulfurization of the molecule have been investigated.The bridge adsorption structure of thiophene leads to a thiol via an activated reaction with an energetic barrier of 0.30 eV.This second step is slightly difficult,and dissociation into a C4H4 fragment and a sulfur atom is possible,with an energetic barrier of 0.40 eV.     

Density Functional Theory Study of C2Hx（x=4～6） Adsorption on the Fe（110） Surface

The density functional theory(DFT) and self-consistent periodic calculation were used to investigate the C2Hx(x = 4～6) species adsorption on the Fe(110) surface. The adsorption energy and equilibrium geometry of the species C2Hx(x = 4～6) on four possible sites(top,hcp,SB and LB) on the Fe(110) surface were predicted and compared. Mulliken charges and density of states analysis of the most stable site have been discussed. It is found that the species of C2H6 and C2H5 are adsorbed strongly on the Fe(110) surface with calculated adsorption energy of -80.24 and -178.89 kJ·mol-1 at the Fe-LB(long-bridge) ,respectively. However,the C2H4 is adsorbed strongly on the Fe(110) surface with calculated adsorption energies of -114.96 kJ·mol-1 at the top. The results indicate that the charge transferring process can be completed by chemisorption between Fe(110) surface and the species. Moreover,the chemical bands can be formed by chemisorptions between the Fe(110) surface and the species,too.     

Density Functional Theory Study on the Adsorption of CN on Transition Metal M（100） （M = Ni,Pd, Pt,Cu, Ag and Au） Surfaces

The adsorption of cyanide on the top site of a series of transition metal M（100） （M = Cu, Ag, Au, Ni, Pd, Pt） surfaces via carbon and nitrogen atoms respectively, with the CN axis perpendicular to the surface, has been studied by means of density functional theory and cluster model. Geometry, adsorption energy and vibrational frequencies have been determined, and the present calculations show that the adsorption of CN through C-end on metal surface is more favorable than that via N-end for the same surface. The vibrational frequencies of CN for C-down configuration on surface are blue-shifted with respect to the free CN, which is contrary to the change of vibrational frequencies when CN is adsorbed by N-down structure. Furthermore, the charge transfer from surface to CN causes the increase of surface work function.     

A MODEL POTENTIAL FOR CHEMISORPTION:CO+Ni(100)

A model LEPS potential has been applied to describe the interac-tion of carbon monoxide with the Ni(100)crystal face.The binding energiescomputed from the potential function agree with the trend of previous theo-retical calculations and experimental results,with the hollow site most stable,the bridge site intermediate and the on-top position least stable.The twiatomicadsorption is also possible,which is metastable.     

Study of H2O and HOCH2CH2OH Adsorption on the Relaxation Surface of β-Si3N4（0001） by Density Functional Theory

Density functional theory （DFT） B3LYP method is used to theoretically investigate the adsorption conformations of H2O and glycol on the relaxation surface of β-Si3N4（0001） with cluster models. For H2O, the most stable structure is that adsorbed through the H atom lying above a N（3） site of the relaxation surface of β-Si3N4（0001）; while for glycol, it is the one adsorbed via the H atom lying above the center of Si（2） and N（3） of the same relaxation surface. The adsorption energy, adsorption bond and transfer electrons of the two adsorbed substances prove that glycol is easy to be adsorbed on the relaxation surface of β-Si3N4（0001）.     

The origin of the site preference of H adsorption on Pd(100)

Spin-polarized density functional theory(DFT)calculations are carried out to determine the site preference of H adsorption on Pd(100)surface and subsurface.We carefully scrutinize the energy difference between different patterns at=0.50 ML and confirm the LEED observation that surface adsorption can form c(2×2)ordering structure.On the contrary,we disclose that p(2×1)structure become more favorable than c(2×2)for subsurface adsorption.These site preferences are rationalized via an analysis of the layer and orbital resolved density of states.Furthermore,we propose that the interstitial charge as a key factor determining the preferred H adsorbed site.     

Ferric perchlorate-mediated radical reactions of [60]fullerene

Transition-metal-salt-mediated radical reactions of fullerenes have attracted extensive attention as a new and important method for fullerene functionalization. The application of relatively cheap and easily available ferric perchlorate (Fe(ClO 4 ) 3 ) to the synthesis of [60]fullerene (C 60 ) has demonstrated remarkable advantages and afforded a series of novel fullerene derivatives. In this review we present our recent progress in this area and summarize the reactions of C 60 with malonate esters, β-keto esters, nitriles, aldehydes/ketones, and arylboronic acids in the presence of Fe(ClO 4 ) 3 to afford the C 60-fused disubstituted lactones, C 60-fused hemiketal, C 60-fused dihydrofuran, C 60-fused oxazoles, C 60-fused 1,3-dioxolanes, and fullerenyl boronic esters. The possible reaction mechanisms for the above-mentioned reactions are also described in detail.     

Adsorption and Diffusion of O Atoms on Ag（210） Stepped Surface

The O-Ag(210)surface adsorption system was studied via the five-parameter Morse potential theory.Meanwhile,the 2O-Ag(210)system was investigated via the extended London-Eyring-Polanyi-Sato(LEPS)potential theory to learn the interaction between the adsorption states.Calculated results demonstrate that there are two stable on-surface adsorption sites(B and H)for O atoms on Ag(210)stepped surface.And the perpendicular vibrations are 30.3 and 42.9 meV,which are close to that observed in high resolution electron energy loss spectroscopy(HREELS).Also,there exists an octahedral subsurface adsorption state with a high vibrational frequency,and the interaction between the on-surface and subsurface O species is slight.The mode at 54.6 meV,which is close to that observed in HREELS(54-56 meV),is because of the vibration of the O atom on B site under the influence of that on H site.     

Theoretical study on the reaction mechanism of CN radical with ketene

The bimolecular single collision reaction potential energy surface of CN radical with ketene (CH2CO) was investigated by means of B3LYP and QCISD(T) methods. The calculated results indicate that there are three possible channels in the reaction. The first is an attack reaction by the carbon atom of CN at the carbon atom of the methylene of CH2CO to form the intermediate NCCH2CO followed by a rupture reaction of the C-C bond combined with -CO group to the products CH2CN CO. The second is a direct addition reaction between CN and CH2CO to form the intermediate CH2C(O)CN followed by its isomerization into NCCH2CO via a CN-shift reaction, and subsequently, NCCH2CO dissociates into CH2CN CO through a CO-loss reaction. The last is a direct hydrogen abstraction reaction of CH2CO by CN radical. Because of the existence of a 15.44 kJ/mol reaction barrier and higher energy of reaction products, the path can be ruled out as an important channel in the reaction kinetics. The present theoretical computation results, which give an available suggestion on the reaction mechanism, are in good agreement with previous experimental studies.     

Studies on the binding of vinpocetine to human serum albumin by molecular spectroscopy and modeling

The interaction between vinpocetine(VPC) and human serum albumin(HSA) in physiological buffer(pH 7.40) was investigated by fluorescence,FT-IR,UV-vis absorption and molecular modeling.VPC effectively quenched the intrinsic fluorescence of HSA via static quenching.The binding site number n and apparent binding constant K_a,corresponding thermodynamic parametersΔG,ΔH andΔS at different temperatures were calculated.The synchronous fluorescence and FT-IR spectra were used to investigate the structural change of HSA molecules with addition of VPC.Molecular modeling indicated that VPC could bind to the site I of HSA and hydrophobic interaction was the major acting force,which was in agreement with the binding mode study.     

Studies on Reaction Mechanism Between Sparfloxacin and Bovine Serum Albumin

The binding of sparfloxacin and bovine serum albumin(BSA) in aqueous solution was studied by means of fluorescence and absorbance spectra, and the interactions influenced by Fe^3 and Cu^2 were explored. Based on the Scatchard‘s site binding model and fluorescence quenching, practical formulas for a small molecule ligand attaching to a bio-macromolecule are proposed. The binding parameters were measured according to the suggested models, and the binding distance, the transfer efficiency of energy between sparfloxacin and BSA were obtained in view of the F6rster theory of non-radiation energy transfer. The effect of sparfloxacin on the conformation of BSA was analyzed by means of synchronous fluorescence spectroscopy.     

Adsorption of Fe（CO）4 on the Sidewall of Boron Nitride Nanotubes： A Periodic DFT Study

The adsorption of Fe（CO）4 on various types of boron nitride nanotubes （BNNTs） areinvestigated by employing density functional theory. Our results indicate that Fe（CO）4 prefers to adsorb on the top of nitrogen atom via Fe atom, and the electronic property analysis indicates that the adsorption of Fe（CO）4 can reduce the band-gap of BNNTs.