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The characteristics of active sites on the surface of albite were theoretically analyzed by density functional theory, and the activation of the C-H bond of methane using an albite catalyst and the reaction mechanism of preparing C2 hydrocarbons by nonoxidative coupling were studied. There are two frustrated Lewis pairs (FLPs) on the (001) and (010) surfaces of albite; they can dissociate H2 under mild conditions and show high activity for the activation of methane C-H bonds. CH4 molecules can undergo direct dissociative adsorption on the (010) surface, whereas a 50.07 kJ/mol activation barrier is needed on the (001) surface. The prepared albite catalyst has a double combination function of the (001) and (010) surfaces; these surfaces produce a spillover phenomenon in the process of CH4 activation reactions, where CH3 overflows from the (001) surface with CH3 adsorbed on the (010) surface to achieve nonoxidative high efficiently C-C coupling with an activation energy of 18.51 kJ/mol. At the same time, this spillover phenomenon inhibits deep dehydrogenation, which is conducive to the selectivity of the C2 hydrocarbons. The experimental results confirm that the selectivity of the C2 hydrocarbons is maintained above 99% in the temperature range of 873 K to 1173 K. [ABSTRACT FROM AUTHOR]

Sulfidization-amine is the most effective method for the recovery of smithsonite (ZnCO 3 ), however the interface interaction details remain unclear. The sulfidization-amine flotation mechanism of smithsonite has been studied by Density Functional based Tight Binding (DFTB+) method in this paper. The slab model of ZnCO 3 (1 0 1) surface was built and the adsorptions of a monolayer of OH − , HS − and S 2− ions were conducted to model the hydration effect of water and the sulfidization effect on the ZnCO 3 (1 0 1) surface adsorption. On the primitive smithsonite surface, the adsorption of dodecylamine (DDA) is stronger than dodecyl secondary amine (DSA) and dodecyl tertiary amine (DTA). However, DDA hardly interacts with the hydrated ZnCO 3 (1 0 1) surface. Under the low concentration of Na 2 S, HS − ions form a Zn SH SH structure on the ZnCO 3 (1 0 1) surface, which hinders the interaction between DDA and surface Zn atoms. Under the high concentration of Na 2 S, a layer of ZnS is formed on ZnCO 3 (1 0 1) surface, which is favorable for the adsorption of DDA on the surface. This is consistent with the flotation practice where smithsonite flotation requires a large amount of sodium sulfide. The results could provide a microscopic investigation into the sulfidization-amine flotation mechanism of smithsonite. [ABSTRACT FROM AUTHOR]

Oxidation of galena (PbS) is of crucial importance in environmental and geochemical processes. Hydrophobic nature of galena surface hinders the adsorption of water, which involves and determines the finally oxidative product of galena. In this work, DFT simulations of the adsorption of O 2 and H 2 O on the hydrophobic galena surface have been performed. Results show that the isolated O 2 molecule is dissociated and adsorbed on the S atoms of galena surface, and the isolated H 2 O molecule hardly interacts with the hydrophobic galena surface. However, the dissociation of both H 2 O and O 2 molecules occur after coadsorption, and water molecule dissociates into O w and H radicals, which then react with surface S atom and adsorbed O 2 molecule to form S O w radical and hydrogen peroxide, respectively. Further adsorption of hydrogen peroxide on surface Pb atoms produces lead hydroxyl radicals. This work could provide microscopic insight into the mechanism of galena oxidation. [ABSTRACT FROM AUTHOR]

Abstracts In froth flotation the molecular interaction between reagents and mineral surfaces take place at the solid liquid interface. In this paper, the effect of water molecule on the three typical thiol collectors (xanthate, dithiocarbomate and dithiophosphate) interactions at the galena (PbS) and sphalerite (ZnS) surfaces has been studied adopting density functional theory (DFT). The results suggests that the presence of water molecule shows a greater influence on the electron distribution of ZnS surface than PbS surface, and reduce the reactivity of ZnS surface atoms but improves the reactivity of PbS surface atoms during the reaction with xanthate. Water adsorption could also reduce the covalent binding between Zn and S atoms but have little influence on Pb-S bond. In the presence of water, xanthate, dithiocarbomate (DTC) and dithiophosphate (DTP) could not adsorb on the sphalerite surface. And for galena (PbS) surface, the interaction of DTP is the strongest, then the DTC and the interaction of xanthate is the weakest. These results agree well with the flotation practice. [ABSTRACT FROM AUTHOR]

Abstract: The adsorption of O2 on a sphalerite surface with vacancies and impurities is investigated through first-principle calculations based on density functional theory (DFT). The calculated results show that O2 adsorption is unavailable on perfect sphalerite surfaces, while the presence of vacancies (e.g., Zn-vacancy and S-vacancy) and impurity atoms (such as Fe, Mn, Cu and Cd) energetically favors the adsorption of O2. The results show that the adsorption energy of O2 on a S-vacancy surface is −408.25kJ/mol, which is stronger than that of a Zn-vacancy surface at −218.55kJ/mol. For a Zn-vacancy surface, the O 2p orbital interacts strongly with the S 3p orbital, and electrons transfer from the S atom to the O atom, which results in the oxidation of S. For the S-vacancy, the O 2p orbital interacts strongly with the Zn 3d orbital, and electrons transfer from the Zn atom to the O atom, which results in the oxidation of Zn. The adsorption energies of O2 on the sphalerite surface with Fe, Mn, Cu and Cd impurities are −181.40kJ/mol, −146.66kJ/mol, −95.53kJ/mol and −55.96kJ/mol, respectively, which indicates that Fe-bearing sphalerite is easily oxidized, while Cd-bearing sphalerite is not easily oxidized. The oxygen molecule dissociates on Fe-, Mn- and Cd-bearing sphalerite surfaces, while oxygen does not dissociate on the Cu-bearing surface. The 3p orbital of S and the 3d orbital of Fe, Mn and Cu atoms donate electrons to the antibonding orbital of the O atom, which enhances the bonding of oxygen with the sphalerite surface. However, the 4d orbital of the Cd atom donates fewer electrons, which weakens the bonding of oxygen with the surface. [Copyright &y& Elsevier]

• The effect of steric hindrance on xanthate adsorption with sphalerite is studied. • Surface S atoms coordinated with Zn atom hinder the Zn reaction spatially. • Adsorption of surface Zn with xanthate S atom has to overcome a potential barrier. • Cu-activation could reduce the energy barrier caused by steric hindrance effect. The influence of steric hindrance effect on xanthate adsorption on sphalerite surface has been studied by adopting density functional theory (DFT). On the relaxed sphalerite (1 1 0) surface, one surface zinc atom coordinates with three sulfur atoms and is located in the center of a planar triangular structure. The sulfur atom with a large atomic radius could spatially hinder the zinc atom, which subsequently results in steric hindrance effect. Consequently, the interaction of xanthate S atoms with surface Zn has to overcome a potential barrier caused by steric hindrance effect. In addition, the DFT simulation and LST search confirmed that the replacement of surface Zn atom by Cu atom could decrease the energy barrier caused by steric hindrance effect, which is favorable for the adsorption of xanthate. The results could explain why ethyl xanthate with short chain length is hard to adsorb on the clean sphalerite surface, but can strongly adsorb on the Cu-activated sphalerite surface. [ABSTRACT FROM AUTHOR]

• Interaction mechanism of three sulfydryl collectors with Au is studied by DFT. • Three collectors' collecting performance is predicted by frontier orbital energy. • Water droplets wetting process on Au surface with/without collectors is discussed. • Collecting performance of three collectors over Au is DTPI > ADD > AMX. Amyl xanthate (AMX), ammonium dibutyl dithiophosphate (ADD) and diisobutyl dithiophosphinate (DTPI) have proved to be common and effective sulfydryl collectors for gold flotation. In this study, density functional theory (DFT) and molecular dynamics (MD) methods are used to investigate the interaction mechanism and collecting performance of three sulfydryl collectors with Au(1 0 0) surface. The adsorption energy of DTPI is −283.30 kJ/mol, which is the largest among the three, suggesting its chemisorption on gold surface is the most stable. This is agreed with the prediction of polarizability and frontier orbital energy difference. The gold-collector interaction on the surface is realized by the bonding of surface Au atom and collector S atom. Density of states (DOS) results suggest that after collector adsorption the delocalization of S 3p orbital is increased, resulting in the enhancement of nephelauxetic effect, and this proves that the covalency of Au − S bond has been facilitated. DOS analysis further confirms that the S atom of DTPI is most likely to form a covalent bond with Au atom because of its strongest reactivity. Besides, molecular dynamics simulation suggests that the wetting process of water droplets on the gold surface would be hindered by the adsorption of three collectors, thus the wettability of the gold surface would change significantly. In summary, it can be considered that the gold collecting performance of three collectors follows the order of DTPI > ADD > AMX. This comparative study is helpful to understand the interaction mechanism between sulfydryl collectors and gold surface. [ABSTRACT FROM AUTHOR]

Pyrite is an attractive material as its good photovoltaic performance; however, the presence of marcasite phase is considered to be detrimental to pyrite as a photovoltaic material due to its low band gap. Density functional theory (DFT) combined with Hubbard U correction was used to perform the calculations on the crystal structures, electronic structures, and optical properties of pyrite and marcasite in the present work. When a U value of 1.5 eV is adopted to Fe 3d, the band gaps of pyrite and marcasite are calculated to be 1.05 eV and 1.33 eV, respectively, compared to 0.54 eV and 1.05 eV without adopting U. It is found that the fundamental band gap in pyrite is formed by Fe 3d-S 3p transition while in marcasite it is formed by Fe 3d-Fe 3d transition. The larger band gap of marcasite suggests that the presence of marcasite could not deteriorate the photovoltaic performance of pyrite. The subsequent calculations on the optical properties confirmed a very similar optical absorption performance of marcasite to pyrite, even finding a redshift of the optical absorption edge of marcasite compared to pyrite in the low energy region and a wider absorption range in the high energy region. These results were associated with the Fe octahedron differences in the crystals, which resulted in a different d orbital splitting scheme proposed in our study. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-Ni-ZIF@NC was applied as anodic material in MFC for the first time. • Doping of polyaniline preserved the original morphology of MOF. • DFT confirmed interaction of material surface and cytochrome active center. • Functional bacteria and cytochromes were described from the level of genes. • This work indicated that carbonized MOFs have the potential for use as anode in MFC. As a green conversion/energy storage device, the practical application of microbial fuel cell (MFC) was limited with its low power generation. The extracellular electron transfer efficiency was one of the key factors affecting the power generation performance of MFC. This paper reported the carbonized derivative Co-Ni-ZIF@NC derived from PANI-doped Co-Ni-ZIF with conductivity, biocompatibility and high electrocatalytic activity. Density functional theory (DFT) confirmed the strong interaction between the electrode surface and microorganisms. The maximum power density of the MFC with Co-Ni-ZIF@NC anode (8.67 W/m3) was 1.47 time higher than that of Co-Ni-ZIF@C-800 (5.96 W/m3). High-throughput sequencing revealed that Co-Ni-ZIF@NC catalyst facilitated the screening of relevant functional microbial communities in microbial membranes, leading to the reinforcement of power generation in MFC. PICRUSt predicted the relative abundance of functional genes, confirmed the spontaneous enrichment behaviour of functional microorganisms to the electrode surface, and identified cytochrome c552 as the dominant role in the EET process. The above foregoing mainly due to the doping of PANI, improved the content of pyrrolic N on the surface of derivatives, protected the original crystal morphology, promoted the approaching behaviour of conductive flagella to the anode surface and shortened the electron transport distance, thus Co-Ni-ZIF@NC exhibited superb bioelectrocatalytic activity. [ABSTRACT FROM AUTHOR]

Abstracts The interaction of collector with the mineral surface plays a very important role in the froth flotation of sphalerite. The adsorptions occurred at the interface between the mineral surface and waters; however most of DFT simulations are performed in vacuum, without consideration of water effect. Semiconductor surface has an obvious proximity effect, which will greatly influence the surface reactivity. To understand the mechanism of xanthate interacting with sphalerite surface in the presence of water molecules, the ethyl xanthate molecule adsorption on un-activated and Cu-activated ZnS(110) surface in the absence and presence of water molecules were performed using the density functional theory (DFT) method. The calculated results show that the adsorption of water molecules dramatically changes the properties of ZnS surface, resulting in decreasing the reactivity of surface Zn atoms with xanthate. Copper activation of ZnS surface changes the surface properties, leading to the totally different adsorption behaviors of xanthate. The presence of waters has little influence on the properties of Cu-activated ZnS surface. The xanthate S atom can interact with the surface S atom of Cu-substituted ZnS surface, which would result in the formation of dixanthogen. [ABSTRACT FROM AUTHOR]

Sulphate-induced corrosion of rebars has been reported to plague the lifespan of concrete structures. However, the associated mechanism underlying this issue is still unclear and therefore deserves further investigation. To fill in this gap, three electrochemical experiments including OCP, EIS and LPR were conducted in this study, alongside XPS and SEM characterizations. Moreover, a Density Functional Theory (DFT) was adopted to simulate the depassivation behaviour of rebar under the sulphate condition. Taking together, the underlying mechanism was disclosed. The results reveal that the presence of sulphate ions appeared to reduce the thickness of the rebar passive film and the Fe3+/Fe2+ ratio in the outer layer. In addition, the threshold value of [SO 4 2−]/[OH−] to cause the depassivation of rebar was experimentally found about 1.26–1.51 in the saturated Ca(OH) 2 solution. Further, the pristine and vacancy-contained α-Fe 2 O 3 (001) surfaces were chosen respectively, to simulate the passive film surface surrounding rebars via DFT. It was found that the SO 4 2− adsorption boosted the formation of surface vacancy, and compared to the pristine surface, the increase in SO 4 2− coverage also promoted the ensuing formation of Fe vacancy on the O vacancy-contained surface. Then, the Fe-O pair vacancy was so formed, and in turn, boosted the following adsorption of SO 4 2− on the passive film of rebars. Combining the experimental results and DFT simulation, the vicious cycle is believed to exist during the sulphate-induced depassivation of rebar, specifically composed of (i) the adsorption of SO 4 2−, (ii) the vacancy formation and increase, and (iii) the progressively enhanced adsorption of SO 4 2−. [Display omitted] • A threshold concentration of sulphate that induce the deterioration of rebar passive film was proposed. • Sulphate attack decreased the thickness of the passive film. • Sulphate mainly destructs the outer layer of rebar passive film. • Interactions of SO 4 2- with the α-Fe 2 O 3 surface were studied based on DFT. • The mutual effect between SO 4 2− adsorption and vacancy formation on the α-Fe 2 O 3 surface was revealed. [ABSTRACT FROM AUTHOR]

[Display omitted] • The electron loss of iron induced by SO 4 2− adsorption was found at atomic scale. • SO 4 2− adsorption induces more serious corrosion of iron than Cl− adsorption. • The present of SO 4 2− would weaken the adsorption of Cl− on iron surface. • The coupled interaction of SO 4 2− and Cl− with iron was revealed at atomic scale. The chloride and sulphate attacks, either individually or parallelly, are the main reasons for the corrosion of the rebar. In this study, the interactions between chloride or/and sulphate and the Fe (1 0 0) surface were simulated by using the density functional theory to reveal the mechanism of rebar corrosion led by the chloride-sulphate adsorption. The adsorption of lone chloride and sulphate on the Fe (1 0 0) surface has been modelled separately. The results show that the interaction of the iron surface with the sulphate is stronger than that with the chloride. The adsorption of sulphate causes more electron loss of the iron surface. In the case of combined chloride-sulphate attack, these two ions mutually compete and thereby, weaken the further interactions with the iron surface. This work may provide guidance for studying the corrosion performance of rebar when subjected to the combined chloride-sulphate attack. [ABSTRACT FROM AUTHOR]

Abstract: First-principles calculations based on density functional theory are performed to study the adsorption and diffusion of hydrogen on ordered Ni3Fe(111) surface and in the bulk. The adsorption of H2 molecule on surface is weak, but the adsorption of H atom on surface is strong. H2 decomposition on surface can easily take place and the largest barrier of H2 decomposition is 0.25 eV. The adsorption of H on surface and in the bulk is both exothermic relative to isolated H atom. The minimum barrier for H diffusion between two nearest sites on surface is 0.11 eV, indicating the H has good mobility on the surface. The minimum barrier for H diffusion from surface to the first subsurface is 0.78 eV. Once H atom diffuses into the first subsurface, it can more easily further diffuse into bulk with barrier values in the range 0.22–0.46 eV, which are very close to those values obtained in ordered bulk Ni3Fe. Moreover, the dependence of adsorption and diffusion properties on surface coverage is also discussed. [Copyright &y& Elsevier]

The impact of a series of precious metal-based (Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au) trimetallic single-cluster catalysts (SCCs) loaded on graphdiyne (U x V y W z @GDY) on the performance of the oxygen reduction reaction (ORR) was systematically analyzed using density functional theory (DFT) calculations. Furthermore, the intricate mechanism underlying the enhancement of the ORR in SCCs was revealed. [Display omitted] • Efficient anchoring of trimetallic SCCs by homogeneously distributed pores of GDY. • Modulate intermediates adsorption energy via electron arrangement difference in SCCs. • Exploring structure–activity of SCCs offers new insights for diverse catalytic fields. Single-cluster catalysts (SCCs) have become a research hotspot due to their abundant active sites and tunable interatomic electronic structure, demonstrating excellent catalytic properties. However, the diversity of metal species in SCCs leads to unclear intrinsic activity toward metals and interaction between different metal species. In this manuscript, the impact of a series of precious metal-based (Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au) trimetallic SCCs loaded on graphdiyne (U x V y W z @GDY) on the performance of the oxygen reduction reaction (ORR) is investigated using first-principles. The results show that the 18 holes of graphdiyne (GDY) efficiently achieve uniform doping of trimetallic clusters. In the U x V y W z @GDY structure, Pt 3 @GDY, Pt 2 Pd@GDY, and AuPdPt@GDY displayed high thermodynamic limit potentials near the top of the volcano plot at 0.79 eV, 0.80 eV, and 0.82 eV, respectively. These catalysts also show low overpotentials of 0.44 V, 0.43 V and 0.50 V, respectively. Deeper scrutiny of the interaction mechanism between *OH and the catalytic sites on Pt 3 @GDY, Pt 2 Pd@GDY, and AuPdPt@GDY unveils the pivotal role of electron transfer and intermetallic interactions in modulating the d-band center. Notably, the observed left shift of the d-band center in these catalysts, leading to the generation of more electron-deficient centers, effectively mitigates the issue of over-absorption between *OH and metal active sites, thereby significantly enhancing *OH desorption. This work provides inspiration for the efficient design of trimetallic SCCs. [ABSTRACT FROM AUTHOR]

Impurity-bearing sphalerite is widely found in nature and plays a vital role in photocatalysis. A systematic theoretical study of the crystal structure, band gap and optical properties of ZnS containing Si, Se and P impurities, respectively, is carried out using density functional theory calculations. The results show that non-metallic atoms in the interstices narrow the ZnS bandgap, improving the electrical conductivity of sphalerite. Analysis of the optical properties reveals that ZnS containing non-metallic impurities produces light absorption at higher energies. Meanwhile, the presence of all three impurities leads to a red shift in the absorption band edge of ZnS, which favors the extension of the light absorption range of sphalerite. The effect of the Si impurity is greater than that of the remaining two impurities, with the highest red shift. This research contributes to the application of sphalerite (ZnS) containing natural impurities in the field of new luminescent materials. • Si changes ZnS from P-type semiconductor to N-type. • Three models of impurity-bearing ZnS are discussed. • Non-metallic atoms in the interstices narrow the ZnS bandgap. • Si、P、Se impurities leads to red shift in the absorption band edge of ZnS. [ABSTRACT FROM AUTHOR]

Reuse of sludge-derived Fe-rich biochar as sludge conditioner is an attractive route for management of waste activated sludge at source. Homogeneous and heterogeneous Fenton reactions have been proved in sludge conditioning with Fe-rich biochar activating H 2 O 2 to enhance sludge dewaterability. The FeAl 2 O 4 phase in Fe-rich biochar was first identified during pyrolysis of sewage sludge after adding both Fe 2 O 3 and Al 2 O 3 , since Fe and Al elements are two of major metal elements in Fe-rich sludge. Compared with the Fe-rich biochar that did not comprise FeAl 2 O 4 phase, the capillary suction time (CST) and specific resistance to filterability (SRF) of the sludge conditioned with the Fe-rich biochar comprising FeAl 2 O 4 phase could be efficiently decreased by 23% and 44%, respectively. The results indicated that FeAl 2 O 4 phase in Fe-rich biochar could improve sludge dewaterability by enhancing heterogeneous Fenton reaction. Synergistic effect between Fe and Al in FeAl 2 O 4 contributed to weak the O–O bond in H 2 O 2 and reduce the activation energy of H 2 O 2 decomposition for enhancing · OH generation, which could be explained by density functional theory (DFT) calculations for the first time. Thus, the decomposition rate of H 2 O 2 and the amount of · OH generation were obviously promoted by FeAl 2 O 4 phase in sludge-derived biochar during sludge conditioning, attributing to the destruction of sludge flocs, the release of bound water, and the improvement of sludge dewaterability. Image 1 • Phase transformations of Fe and Al species in sludge during pyrolysis were studied. • FeAl 2 O 4 in biochar contributed to heterogeneous Fenton during sludge conditioning. • The model of H 2 O 2 decomposition on surface of FeAl 2 O 4 was proposed by VASP. • Synergistic effect of Fe and Al of FeAl 2 O 4 enhanced the adsorption energy of H 2 O 2. • Heterogeneous Fenton reaction contributed to destroy inner part of sludge flocs. [ABSTRACT FROM AUTHOR]

The interactions between formaldehyde (HCHO) molecule and TiO 2 (1 0 1) surface without and with water and oxygen were studied using density functional theory calculations. The adsorption energy of HCHO adsorption on TiO 2 surface without water and oxygen is −360.96 kJ/mol, and HCHO molecule is not dissociated. The oxygen and carbon atoms of HCHO are bonded to the titanium and oxygen (O1) atoms of TiO 2 surface, respectively, and form a dioxymethylene (CH 2 O 2 ) structure. The adsorption energy of HCHO adsorption on TiO 2 surface system with water and oxygen is −723.40 kJ/mol, and O 2 , H 2 O and HCHO molecules are all dissociated. HCHO molecule not only interacts with TiO 2 surface, but also combines with O 2 molecule. Two C H bonds of HCHO are broken, one hydrogen atom (H1) is bonded to the oxygen atom (O2) of O 2 , while another hydrogen atom (H2) is bonded to the O atom (O1) of TiO 2 surface. The remaining C O bond that the dissociated and new formed H O bonds can be oxidized to form carbon dioxide and water in subsequent action by oxygen from the atmosphere. H 2 O and O 2 molecules have a great effect on the degradation process of HCHO molecule on TiO 2 (1 0 1) surface. [ABSTRACT FROM AUTHOR]

The adsorption of cyanide ions (CN − ) on pyrite, marcasite and pyrrhotite surfaces was studied using density functional theory. The depressing effects of CN − on these three minerals were then investigated by flotation tests. The calculated results show that the adsorption energy of CN − on the marcasite surface is the largest, −374.91 kJ/mol; followed by pyrrhotite, −364.34 kJ/mol; and pyrite, −327.94 kJ/mol. These results indicate that the interaction between CN − and marcasite surface is the strongest, then pyrrhotite, followed by pyrite. The depression effect of cyanide on the pyrite, marcasite and pyrrhotite in concentrate with increasing NaCN dosage was analysed by X-ray diffraction (XRD). The results show that the depression effect is in decreasing order of marcasite, pyrrhotite and pyrite, and the greater the cyanide dosage, the stronger depression effect is, which is in good agreement with the calculated results. [ABSTRACT FROM AUTHOR]

The galvanic interaction between pyrite and galena surface has been investigated using density functional theory (DFT) method. The calculated results show that galvanic interactions between pyrite and galena surface are decreased with the increase of contact distance. The galvanic interactions still occurs even the distance larger than the sum of two atoms radius (≈2.8 Å), and the limit distance of galvanic interaction between galena and pyrite surface is about 10 Å, which is consistent with the quantum tunneling effect. Through Mulliken charge population calculation, it is found that electrons transfer from galena to pyrite. For galena surface, Pb 6s and 6p states lose electrons and S 3p state loses a small amount of electrons, which causes the electron loss of galena. For pyrite surface, Fe 4p state obtains large numbers of electrons, resulting in the decrease of positive charge of Fe atom. However, the 3p state of S atom loses a small numbers of electrons. The reactivity of mineral surface has also been studied by calculating the frontier orbitals of minerals. Results suggest that the highest occupied molecular orbital (HOMO) coefficients of galena are increased whereas those of pyrite are decreased with the enhancing galvanic interaction, indicating that the oxidation of galena surface would be enhanced due to the galvanic interaction. The Fukui indices and dual descriptor values of surface atoms suggest that the nucleophilicity of the galena surface increases, meanwhile, the electrophilicity of pyrite surface increases with the decrease of the contact distance. In addition, the density of states (DOS) of atoms results show that the activity of electrons in Pb 6s and 6p orbitals enhances while the activity of electrons in Fe 3d orbitals weaken due to the galvanic contact between minerals. [ABSTRACT FROM AUTHOR]

• Coadsorption of O 2 and H 2 O on the Fe (1 0 0) surface could produce Fe-O and Fe-OH. • Further oxidation of the iron surface causes O to react with Fe-OH to form FeOOH. • DFT simulation provides microscopic insight into the corrosion mechanism of steel bar. Corrosion of steel bar is a major problem influencing the long-term performance of reinforced concrete structures. It is known that both oxygen and water involve in the initiation of corrosion of steel bars and determine the formation of the final corrosion products. In this paper, the interaction of oxygen and water on the Fe (1 0 0) surface have been simulated by using density functional theory (DFT), to study the mechanism of steel bar corrosion and the formation process of the corrosion product (FeOOH). The results show that the preadsorbed water on the iron surface has little effect on the O 2 adsorption, but the adsorption of O 2 weakens the interaction between H 2 O and iron surface. On the other hand, the preadsorbed oxygen strengthens the adsorption of H 2 O via the formation of hydrogen bond between the O atom of O 2 and the H atom of H 2 O. Strong interaction of oxygen and water promotes the dissociation of O 2 and H 2 O molecules on the Fe (1 0 0) surface, and forms a Fe-O and two Fe-OH groups on the iron surface. Moreover, it is found that the Fe-OH group is unstable, and reacts easily with the newly introduced O atom to form the FeOOH, which confirms that FeOOH is the main corrosion product of steel bar instead of Fe-OH. This work could provide a microscopic insight into the mechanism of reinforcement steel corrosion. [ABSTRACT FROM AUTHOR]