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Adsorption and activation of CO2 can be considered as the first steps of the reaction mechanism of methanol synthesis via CO2 hydrogenation on Cu-based bimetallic clusters. In this work, the adsorp...

A facile one-pot method for synthesizing different morphologies of PdCu nanocrystals (NCs) has been introduced. The morphologies of PdCu NCs can be controlled by tuning the amount of the single cap...

The electronic structures and optical properties of the rutile TiO 2 doped by C, (2Sb, C), (2Nb, C), (Nb + Sb, C) have been investigated by density functional theory plus U calculations. It is found that (2Sb, C), (2Nb, C), (Nb + Sb, C) codoping results in band gap narrowing, due to the appearance of the mid-bandgap states from C 2p and the introduction of Sb 5s and Nb 4d states. In addition, the rutile TiO 2 codoped by (Nb + Sb, C) and (2Nb, C) is much more effective for the enhancement of visible light absorption than that for C monodoping and (2Sb, C) codoping.

Using first-principle calculations within density functional theory, we investigate the energetics and kinetics of small carbon clusters on a bimetallic Cu/Ni(111) surface, which is proposed by replacing the subsurface of Ni(111) with a single layer of Cu. For small carbon clusters up to 10 atoms, the adsorption strength on the Cu/Ni(111) surface is much stronger than that of the same structure on either Ni(111) or Cu(111). Furthermore, linear chains are found to be more favorable than rings. It is also found that linear carbon chains on the Cu/Ni(111) surface can diffuse quickly, even faster than the adatom. Moreover, their mobility is higher than that of the same structure on Ni(111) (or Cu(111) for dimer diffusion).

In this study, hybrid density functional theory calculations have been used to investigate the electronic structures of (Mg, S), (2Al, S), (Ca, S), and (2Ga, S) codoped anatase TiO2, aiming at improving their photoelectochemical performance for water splitting. It is found that the acceptor metals (Mg, Al, Ca, and Ga), assisting the coupling of the incorporated S with the neighboring O in TiO2, lead to the fully occupied energy levels in the forbidden band of TiO2, which is driven by the antibonding state π* of the S–O bond. It is also found that the metal-assisted S–O coupling can prevent the recombination of the photo-generated electron–hole pairs and effectively reduce the band gap of TiO2. Among these systems, the (Mg, S) codoped anatase TiO2 has the narrowest band gap of 2.206 eV, and its band edges match well with the redox potentials of water. We propose that this metal-assisted S–O coupling could improve the visible light photoelectrochemical activity of anatase TiO2.

In order to combine the advantages of both 0D and 1D nanostructured materials into a single catalyst, density functional theory (DFT) calculations have been used to study the PdCu alloy NP-decorated Cu nanotubes (PdCu@CuNTs). These present a significant improvement of the electrocatalytic activity of formic acid oxidation (FAO). Motivated by our theoretical work, we adopted the seed-mediated growth method to successfully synthesize the nanostructured PdCu@CuNTs. The new catalysts triple the catalytic activity for FAO, compared with commercial Pd/C. In summary, our work provides a new strategy for the DFT prediction and experimental synthesis of novel metal NP-decorated 1D nanostructures as electrocatalysts for fuel cells.

Understanding the phase diagram is the first step to identifying the structure-performance relationship of a material at the nanoscale. In this work, a modified nanothermodynamical model has been developed to predict the phase diagrams of Ag-Co nanoalloys with the size of 1 ∼ 100 nm, which also overcomes the difference in the predicted results between theory and simulation for the first time. Based on this modified model, the phase diagrams of Ag-Co nanoalloys with various polyhedral morphologies (tetrahedron, cube, octahedron, decahedron, dodecahedron, rhombic dodecahedron, truncated octahedron, cuboctahedron, and icosahedron) have been predicted, showing good agreement with molecular dynamics simulations at the nanoscale of 1 ∼ 4 nm. In addition, the surface segregation of Ag-Co nanoalloys has been predicted with a Co-rich core/Ag-rich surface, which is also consistent with the simulation results. Our results highlight a useful roadmap for bridging the difference between theory and simulation in the prediction of the phase diagram at the nanoscale, which will help both theorists and experimentalists.

By means of hybrid density functional theory (DFT) computations, we found that (Li,K)-codoped WO3 shows a significantly enhanced near-infrared (NIR) absorption ability for smart windows, and investigated the influence of doping through the analysis of the electronic structures of pure and doped hexagonal WO3. Furthermore, this codoped material, with a hexagonal tungsten bronze nanostructure, was successfully prepared via a simple one-step hydrothermal reaction for the first time. Transmission electron microscopy images showed that the as-prepared products possessed a nanorod-like morphology with diameters of about 5-10 nm. It was demonstrated that (Li,K)-codoped WO3 presents a better NIR absorption ability than pure, Li-monodoped or K-monodoped WO3, which is in good agreement with our theoretical predictions. The experiment and simulation results reveal that this enhanced optical property in NIR can be explained by the existence of high free electrons existing in (Li,K)-codoped WO3.

Applicability of rutile Ti 1− x In x O 2 as a new p-type TiO 2 -based transparent conducting oxide has been investigated by examining their electronic structures and optical absorption properties, based on density functional theory plus U calculations. It is found that In doped rutile TiO 2 displays metal-like characteristics and the edges of the optical absorption spectra are gradually blue-shifted with the increase of In doping concentration. In addition, the proper In doping level, 12.5% ≤ x ≤ 18.75%, is proposed in order to achieve excellent conducting properties and high transparency in the visible light region from the calculations of optical absorption spectra in this work.

We use periodic density functional theory to investigate the adsorption properties of O and OH on different Pt–Ni alloy systems, including Pt(1 1 1), Pt(1 1 1) with surface Ni (surface for short), PtNi3(1 1 1), PtNi(1 1 1), Pt3Ni(1 1 1), Pt(1 1 1)-skin-Pt3Ni, Pt(1 1 1) with subsurface Ni (subsurface for short), and Ni(1 1 1). It is found that the adsorption strength of both O and OH displays the order of subsurface

We have used density functional theory (DFT) to investigate the adsorption and first dissociation step of ammonia on both clean and Pt-covered TiO2 rutile (1 1 0) surfaces. On clean rutile TiO2 (1 1 0) surface, NH3 and NH2 prefer to chemisorb on the five-coordinated titanium (Ti5c) site, and H is adsorbed favorably on the bridging oxygen (01) site, while a single Pt atom prefers to adsorb on the hollow (H2) site. It is found that the preadsorbed Pt atom enhances significantly the adsorption of NH3, NH2 and H species on rutile TiO2 (1 1 0) surface by binding with Pt adatom directly. It is also found that the first dissociation step of ammonia (NH3 >= NH2 + H) on the clean rutile TiO2 (1 1 0) surface is endothermic by 0.89 eV, and no transition state exists. In addition, the first dissociation step of ammonia on Pt-covered rutile TiO2 (1 1 0) surface is found to be endothermic by only 0.43 eV, but presents an activation energy barrier of 1.82 eV. A comparison of the adsorption and first dissociation step of ammonia on rutile TiO2 (1 10) surface with and without Pt adatom has been discussed. Investigations indicate that the adsorbed Pt adatom on clean rutile TiO2 (1 1 0) surface not only changes the surface electron structure, but also varies the reaction pathways by participating in the reaction. It is expected that our results would provide useful information for the development of catalyst for NH3 dissociation. (C) 2011 Elsevier B.V. All rights reserved.

The question of the influence of the environment on the structure and thermodynamic state of a bimetallic cluster is examined, using Metropolis Monte Carlo methods. An embedded atom model is used to estimate metal energies. The environment is modeled at a generic level as a rigid matrix which atoms interact with the atoms of an embedded Au-Pd cuboctahedral cluster via a Lennard Jones (LJ) potential. The high sensitivity of the cluster properties on its environment is demonstrated by scaling the LJ potential. It is found that the strength of the interfacial interactions completely determines surface segregation. Full segregation with either Au or Pd at the surface favors the occurrence of stable alloy phases in the cluster core while the subsurface layer acts as a buffer accommodating both the induced surface segregation and the inner composition constrained by phase stability. Cluster surface disorder induced by an amorphous matrix limits interface segregation and phase stability in the cluster core, even when the interfacial interaction strength is weak. The contrast between the epitaxial and amorphous matrix cases over a wide range of interface energies suggests the importance in the thermodynamic properties of the cluster core of the interfacial atomic arrangement in the matrix.

The melting temperature and behaviour of gold nanowire in a single-walled carbon nanotube (SWNT) were investigated in detail using molecular dynamics simulations. The results showed that the melting temperature of the enclosed Au nanowire is lower than its bulk counterpart and higher than that observed for free-standing ones. Different from the melting behaviour of freestanding Au nanowires, the melting of Au nanowires enclosed in SWNTs with tube diameters (D) in the range 1.08 nm

Molecular dynamics simulations were used to investigate the cluster-size, tube-size and metal–tube interaction effects on the melting of Pd clusters encapsulated inside carbon nanotubes (CNTs). The second moment approximation to the tight-binding potential was used to model Pd–Pd metal–metal interaction and the Tersoff potential was used for C–C interactions. Pd–C interaction was modelled by the typical weak van der Waals Lennard-Jones (VDW-LJ) potential to understand the cluster-size and tube-size effects on the thermal behaviour of supported Pd clusters. Linear decrease in cluster melting point with the inverse in cluster diameter is predicted for the CNT containing Pd clusters, well known as Pawlow's law. It is also found that the melting temperature of the supported Pd cluster is much lower than that of free one, and the rearrangement and transformation of the cluster at higher temperatures before melting are responsible for this lowering. In this case, the downward shift is independent of the CNT dia...

The original Supplementary Information file published with this Article was an older version; it was missing several Tables, and the Methods section was a duplicate of that from the main article. A new Supplementary Information file has been uploaded with these issues corrected.

The dissociation of carbonaceous molecules on the surface of a nano-sized Ni crystal induces deep morphological changes way below the melting temperature, as imaged by Field Ion Microscopy. In this Letter, classical Molecular Dynamics (MD) was used to demonstrate that carbon adsorption triggers Ni surface diffusion. More precisely, single adsorbed carbon atoms, preferentially bound to 5-fold surface sites, enhance thermally activated Ni diffusion. A mechanism is identified by which adsorbed carbon promotes the rupture of surface Ni atoms from their lattice position. This leads to a destabilization of edges between facets of the Ni crystal.

Classical molecular dynamics and Metropolis Monte Carlo simulations were carried out to investigate the thermal stability and melting behaviors of free-standing Pd-Pt bimetallic nanowires (NWs) with pentagonal multi-shell-type (PMS-type) structure in the whole composition range. Equilibrium configurations at 100 K are predicted in the semi-grand canonical ensemble. Pd-Pt PMS-type NWs are stable with a multishell structure of alternating Pd and Pt compositions and Pd segregating systematically to the surface. On thermal heating, an interesting composition-dependent structural transformation from the PMS-type to face-centred-cubic (FCC) by overcoming a high energy barrier is observed for Pd-Pt bimetallic NWs before the melting. Consequently, the system energy is decreased. The FCC structure is found more stable than PMS-type over the whole range of composition. The melting of Pd-Pt bimetallic NWs is also studied. It is found to start at the edges, then propagate over the whole surface, and next to the interior. It occurs in a composition-dependent range of temperature.

The coalescence of Au 13 , Au 55 and Au 147 icosahedral clusters encapsulated inside single walled carbon nanotubes (CNTs) of different diameters are investigated using molecular dynamics simulation with semi-empirical potentials. Three steps needed for the formation of encapsulated nanowires are followed in detail, namely, the penetration of clusters in CNTs, the coalescence between two clusters inside CNTs and their accumulation to form wires. It is suggested that no significant energy barrier is encountered during the penetration of free clusters into CNTs provided the CNT radius is large enough, that is, about 0.3 nm larger than the cluster radius. The relative orientation of clusters imposed by the CNT favors their spontaneous coalescence. After coalescence of two clusters, the Au atoms are rearranged to form new structures of cylindrical symmetry that may be seven fold, six fold, five fold, helical or fcc depending on the CNT diameter. The thermal stability of these structures is discussed and the structural properties of nanowires formed by accumulation of many clusters in CNTs are analyzed in detail. A geometrical method is presented which allows the prediction of the structure of multi-shell helical wires, when knowing only the CNT radius. These modeling results suggest the possibility of synthesizing metallic nanowires with controlled diameter and structure by embedding clusters into nanotubes with suitable diameters.

A theoretical method, which combines the first-principle calculations and a canonical Monte Carlo (CMC) simulation, was used to study the structures of Au clusters with sizes of 25–54 atoms supported on the MgO(1 0 0) surface. Based on a potential energy surface (PES) fitted to the first-principle calculations, an effective approach was derived to model the Au–MgO(1 0 0) interaction. The second moment approximation to the tight-binding potential (TB-SMA) was used to model the Au–Au interactions in the CMC simulation. It is found that the Au clusters with sizes of 25–54 atoms supported on the MgO(1 0 0) surface possess an ordered layered fcc epitaxial structure.

A general synthesis strategy to prepare metal nanostructures by self-assembly was proposed by molecular dynamics (MD) simulation. In this simulating synthesis strategy, the metal nanostructures were generated by the self-assembly of the amorphous nanoparticles with the attractive forces of the nanoparticle−nanoparticle interactions by the annealing MD method at high temperatures, and finally, the resulting amorphous metal nanostructures were cooled to 10 K, which could resemble the nanoparticle self-assembly in experiment. By using the simulating synthesis, we obtained the full atomistic models of the shape-controlled metal nanostructures, including Au, Ag−Au, and beaded Ag−Cu nanorods, triangular and hexagonal Ag nanoplates, triangular Ag−Au and hexagonal Au, cubic hollow Fe, and Ag−Au nanoframes. It is found that these models are in good agreement with the experimental results. Moreover, we predicted a new metal nanostructure, Au nanoporous framework architecture, which has not been reported in experime...

We use canonical Monte Carlo simulations to study the melting of icosahedral and decahedral onion-ring Pd–Pt bimetallic clusters consisting of 147 atoms. Structural transition from decahedron to icosahedron-like is found for the decahedral onion-ring 147-atom Pd–Pt cluster before melting. Also, the melting point of the decahedral onion-ring 147-atom Pd–Pt cluster is lower than the corresponding icosahedral cluster. In addition, at the higher temperatures after melting, the four-shell onion-ring structure becomes unstable, and can be transformed into the three-shell onion-like structure.

We employ a multiscale theoretical method, which combines the first-principle calculation and a grand canonical Monte Carlo (GCMC) simulation, to predict the adsorption capacity of hydrogen in silicon nanotube (SiNT) arrays at T = 298 K in the pressure range from 1 to 10 MPa. In the multiscale method, the binding energy obtained from the first-principle calculation is used as an input in the GCMC simulation. It is found from the first-principle calculation that the SiNT arrays exhibit much stronger attraction to hydrogen both inside and outside SiNTs, compared to the isodiameter carbon nanotubes (CNTs). The subsequent GCMC simulations indicate that the SiNT arrays present distinct improvements of 106%, 65%, and 52% in the gravimetric adsorption capacity of hydrogen at P = 2, 6, and 10 MPa, respectively, compared to the isodiameter CNTs. This suggests that the SiNT array is a promising candidate for hydrogen storage.

We predict by using atomistic simulations that there exists a new kind of multishell onion-ring structures of bimetallic nanowires and clusters for three systems (A/B = Pd/Pt, Ag/Au, and Ag/Pd). In the structures of multishell onion-ring bimetallic nanowires and clusters, A atoms and B atoms occupy alternately the layers of the nanowires and clusters, thus forming the onion-ring morphology. The simulation results show that the multishell onion-ring structures can be found for the bimetallic nanowires and clusters at 100, 300, and 500 K. In summary, this investigation suggests a new possible morphology for the bimetallic systems at the nanoscale level, and the morphology can be tailored by controlling composition and atomic ordering of two metals. It is expected that the multishell onion-ring structure for bimetallic nanowires and clusters may provide potential applications for the design of catalytic and optical materials.

In this work, we performed a Monte Carlo simulation study on the thermal evolution of icosahedral Pd55, Pd43Pt12, and Pd13Pt42 clusters supported on the MgO(100) surface, using the second-moment approximation of the tight-binding potentials for the metal−metal interactions and the many-body potential energy surface for the metal−MgO(100) interaction. The potential energy surface here is obtained by fitting to ab initio calculation results (Vervisch, W.; Mottet, C.; Goniakowski, J. Phys. Rev. B 2002, 65, 245411). The solid−solid structural transformation from the icosahedral structure to the layered fcc structure is found for the Pd55, Pd43Pt12, and Pd13Pt42 clusters supported on the MgO(100) surface, determined by the changes of the total potential energies and variations of the deformation parameters. It is found that the supported Pd55, Pd43Pt12, and Pd13Pt42 clusters possess the layered epitaxial fcc structure at higher temperatures after structural transformation. In addition, the composition effect o...

A Monte Carlo method has been performed to simulate the thermal evolution of an icosahedral Pt55 cluster encapsulated in the (15, 15) and (20, 20) single wall carbon nanotubes (SWNTs), using the second-moment approximation of the tight-binding potentials for metal−metal interactions. The metal−carbon interactions are modeled by the Lennard-Jones potential, and the carbon atoms on the SWNTs are considered to be fixed. The melting-like structural transformation is found for the icosahedral clusters encapsulated in SWNTs. The melting-like transformation temperatures of the icosahedral clusters encapsulated in SWNTs are estimated from the fluctuations of the total potential energy, which are 280 and 320 K, respectively. The simulations indicate that the melting-like transformation temperature for the encapsulated icosahedral clusters increases with the pore size of SWNTs. At higher temperatures, a stacked structure in layers is found for the encapsulated icosahedral Pt55 clusters. Simulation results reveal th...

Segregation phenomena of Pd–Pt bimetallic clusters with icosahedral and decahedral structures are investigated by using Monte Carlo method based on the second-moment approximation of the tight-binding (TB-SMA) potentials. The simulation results indicate that the Pd atoms generally lie on the surface of the smaller clusters. The three-shell onion-like structures are observed in 55-atom Pd–Pt bimetallic clusters, in which a single Pd atom is located in the center, and the Pt atoms are in the middle shell, while the Pd atoms are enriched on the surface. With the increase of Pd mole fraction in 55-atom Pd–Pt bimetallic clusters, the Pd atoms occupy the vertices of clusters first, then edge and center sites, and finally the interior shell. It is noticed that some decahedral structures can be transformed into the icosahedron-like structure at 300 and 500 K. Comparisons are made with previous experiments and theoretical studies of Pd–Pt bimetallic clusters.

The onion-ring structure is validated in the Pd-Pt bimetallic clusters of total atom numbers 147 and 309 through the Monte Carlo method by using the second-moment approximation of the tight-binding (TB-SMA) potentials, which is conceived in predicting the possible structures of the bimetallic clusters by He et al. [J. Am. Chem. Soc. 2003, 125, 11034] and Hwang et al. [J. Am. Chem. Soc. 2005, 127, 11140]. In the onion-ring structure, Pd atoms and Pt atoms occupy alternate layers of the clusters. The formation of the onion-ring structure can be associated with the fact that the single Pt impurity is favorable to stay in the subsurface layer and the central part of bimetallic clusters.

We have investigated segregation phenomena in Cu–Au bimetallic clusters with decahedral structures at 100 K and 300 K, based on the second-moment approximation of the tight-binding (TB-SMA) potentials by using Monte Carlo method. The simulation results indicate that there are three regions (split, three-shell onion-like and core-shell region) at 100 K and two regions (split and core-shell) at 300 K with the structure of decahedral clusters, as the chemical potential difference Δμ changes. It is found that the structure of decahedral clusters undergoes a division into smaller clusters in the split region. In the core-shell structure, Au atoms are enriched in surface and Cu atoms occupy the core of the clusters because of the different surface energy of Cu and Au. The Au atoms are enriched in the surface shell, and the Cu atoms are in the middle shell, while a single Au atom is located in the center to form the three-shell onion-like structure. The structure and binding energy of smaller clusters after splitting are also discussed. The Au atoms generally lie on the surface of the smaller clusters after splitting.

Despite remarkable efforts have been put into the field of Pt-shelled catalysts containing an atomically thin Pt surface layer for the oxygen reduction reaction (ORR) in the last decade, further development of new Pt-shelled catalysts is still necessary. Here, a new set of Pt-shelled catalysts by subsurface alloying with early transition metals such as Mn and Fe is predicted to be a good candidate for the ORR by using density functional theory (DFT) calculations. Trends in oxygen reduction activity of Pt–alloy catalysts are determined with calculations of oxygen binding by using the slab and cluster models. It is found that the subsurface alloys by the incorporation of submonolayer M (M = Mn and Fe) into Pt(111) in the slab model result in the enhancement of ORR activity, compared with the well-known Pt(111)–skin–M, pure Pt, and Pt3M alloy catalysts. For the cluster model, the Pt12Mn and Pt12Fe clusters are also found to be the optimal catalysts for the ORR. It is expected that this work can open up new opportunities for enhancing the ORR activity of Pt–alloy catalysts by subsurface alloying.

Using a combination of analytic-potential and first-principles density functional theory (DFT) calculations, composition effects on energetics, adsorption energies, and catalytic activity of Au-Pd nanoalloys are investigated, selecting CO oxidation to CO2 as a prototypical reaction and 55-atom Au-Pd clusters with Mackay icosahedral structure as template systems. It is first shown that the Au54Pd1, Au43Pd12, Au42Pd13, and Au12Pd43 nanoalloys with highly symmetric structures are well separated from other nanoalloys due to their special relative stability at the empirical potential and/or DFT levels, with CO adsorption energies on top of Au atoms found to be weakly dependent on composition in a range around 50:50 Au:Pd ratio. The explicit calculation of reaction energy barriers for the CO oxidation process then shows that these are sensitive to the composition of nanoalloys, where Au-rich clusters possess a high catalytic activity and the Au43Pd12 cluster is predicted to have the highest catalytic activity among the clusters here considered. Our results highlight a non-monotonous behavior of the catalytic activities of Au-Pd nanoalloys on composition that is of fundamental interest for the design of new catalysts, but also the subtleties of a delicate interplay of structural and electronic effects in determining reaction energetics, which are difficult to summarize into few, simple prescriptions. (c) 2014 Elsevier Inc. All rights reserved.

We use hybrid density functional calculations to find that the monolayer silicane (SiH) and the anatase TiO2(101) composite (i.e. the SiH/TiO2 heterojunction) is a promising TiO2-based photocatalyst under visible light. The band gap of the SiH/TiO2(101) heterojunction is 2.082 eV, which is an ideal material for the visible-light photoexcitation of electron-hole pairs. Furthermore, the SiH/TiO2(101) heterojunction has a favorable type-II band alignment and thus the photoexcited electron can be injected to the conduction band of anatase TiO2 from that of silicane. Finally, the proper interface charge distribution facilitates the carrier separation in the SiH/TiO2(101) interface region. The electron injection and carrier separation can prevent the recombination of electron-hole pairs. Our calculation results suggest that such electronic structure of SiH/TiO2(101) heterojunction has significant advantages over these of doped TiO2 systems for visible-light photocatalysis.

Equilibrium structures, chemical ordering and thermal properties of Pt-Ni nanoalloys are investigated by using basin hopping-based global optimization, Monte Carlo (MC) and molecular dynamics (MD) methods, based on the second-moment approximation of the tight-binding potentials (TB-SMA). The TB-SMA potential parameters for Pt-Ni nanoalloys are fitted to reproduce the results of density functional theory calculations for small clusters. The chemical ordering in cuboctahedral (CO) Pt-Ni nanoalloys with 561 and 923 atoms is obtained from the so called semi-grand-canonical ensemble MC simulation at 100 K. Two ordered phases of L1(2) (PtNi3) and L1(0) (PtNi) are found for the CO561 and CO923 Pt-Ni nanoalloys, which is in good agreement with the experimental phase diagram of the Pt-Ni bulk alloy. In addition, the order-disorder transition and thermal properties of these nanoalloys are studied by using MC and MD methods, respectively. It is shown that the typical perfect L1(0) PtNi structure is relatively stable, showing high order-disorder transition temperature and melting point among these CO561 and CO923 Pt-Ni nanoalloys.

The conversion of CO₂ into fuels and chemicals is viewed as an attractive route for controlling the atmospheric concentration and recycling of this greenhouse gas, but its industrial application is limited by the low selectivity and activity of the current catalysts. Theoretical modeling, in particular density functional theory (DFT) simulations, provides a powerful and effective tool to discover chemical reaction mechanisms and design new catalysts for the chemical conversion of CO₂, overcoming the repetitious and time/labor consuming trial-and-error experimental processes. In this article we give a comprehensive survey of recent advances on mechanism determination by DFT calculations for the catalytic hydrogenation of CO₂ into CO, CH₄, CH₃OH, and HCOOH, and CO₂ methanation, as well as the photo- and electrochemical reduction of CO₂. DFT-guided design procedures of new catalytic systems are also reviewed, and challenges and perspectives in this field are outlined.

Molecular simulation has become an important and powerful method dealing with complex systems in the fields of chemistry, materials and bioscience. Chinese scholars have been important contributors...

The composition-dependent equilibrium structure and thermal stability of Pd-Pt clusters with the size of 55 atoms, and CO, O, OH, and O(2) adsorption on these clusters have been studied using molecular simulation based on the Gupta empirical potential and density functional theory (DFT) calculations. It is found that Pd(43)Pt(12) with a three-shell onionlike structure (TS-cluster) exhibits the highest relative stability in both DFT and Gupta levels and also the highest melting point at the Gupta level among these Pd-Pt clusters. In addition, the Pd(43)Pt(12) TS-cluster possesses the weakest CO, O, OH, and O(2) adsorption strength, compared to the Pt(55), Pd(55), and Pd(13)Pt(42) clusters, indicating good catalytic activities toward the oxygen reduction reaction (ORR) among these Pd-Pt clusters considered. We expect that this kind of DFT-guided strategy by controlling the composition could provide a simple way for possibly searching new electrocatalysts.

The structure, energetics, and mobility of carbon aggregates up to 10 atoms on the Ni(111) surface are investigated via first-principles simulations. Chain configurations are predicted to be thermodynamically favored over rings and present a high mobility (with long chains diffusing even faster than adatoms), whereas branched configurations are much less mobile but kinetically robust, as they present substantial energy barriers for interconversion into other species. A model of growth via homogeneous nucleation is proposed in which incoming C atoms generate chains which diffuse rapidly and collect less mobile adatoms in their channels until they meet in an unfavorable configuration and start networking giving rise to starlike branching points, which are homologous to graphene and act as the nuclei of growth. It is argued that the proposed homogeneous nucleation mechanism should be observed experimentally, especially in mild conditions and on low-defect Ni(111) surfaces.

The meltinglike transition of the ${\mathrm{Cu}}_{1}{\mathrm{Au}}_{54}$ and ${\mathrm{Cu}}_{12}{\mathrm{Au}}_{43}$ clusters is investigated by canonical Monte Carlo simulations, based on the second-moment approximation of the tight-binding potentials. The structures of both the ${\mathrm{Cu}}_{1}{\mathrm{Au}}_{54}$ and ${\mathrm{Cu}}_{12}{\mathrm{Au}}_{43}$ clusters, shown to be icosahedral, are obtained from the so-called semi-grand-canonical ensemble Monte Carlo simulation at $100\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. A core-shell structure is found in ${\mathrm{Cu}}_{1}{\mathrm{Au}}_{54}$, with a single Cu atom in the center and 54 Au atoms on the surface and in interior shells of the cluster. On the other hand, ${\mathrm{Cu}}_{12}{\mathrm{Au}}_{43}$ possesses a three-shell onionlike structure, with a single Au atom located in the center, 12 Cu atoms in the middle shell, and 42 Au atoms occupying the surface shell of the cluster. Melting characteristics are observed by the changes in the caloric curve, heat capacity, root-mean-square bond-length fluctuation, and deformation parameter. It is found that doping of ${\mathrm{Au}}_{55}$ with a single Cu atom can sharply raise the melting point of the cluster. In addition, the three-shell onionlike structure can be transformed into the core-shell structure at the higher temperatures after melting. It is also found that surface segregation of Au atoms in ${\mathrm{Cu}}_{1}{\mathrm{Au}}_{54}$ and ${\mathrm{Cu}}_{12}{\mathrm{Au}}_{43}$ occurs in the liquid phase. In addition, the simulation results show that the melting point increases with the concentration of Cu in the 55-atom Cu-Au bimetallic cluster.

The chemical doping method is often adopted to obtain metal-free conducting materials. To date, it is still a great challenge to controllably prepare metal-free semiconducting and conducting materials by tuning the inherent structure of a material. In this work, a class of novel one-dimensional (1D) covalent-organic polymer (COP) has been designed, whose cross-sections are triangular, tetragonal, pentagonal and hexagonal, and their electronic properties are explored. The tetragonal 1D COP exhibits unique phenomena in electronic properties, i.e. the tetragonal COPs with mono- or trilayer defects (odd defects) show semiconducting properties, while they become conductors for the two cases of non- or bilayer defects (even defects). This observation indicates that they comply with the characteristics of semiconducting and conducting switches induced by the odd-even defects. Therefore, we infer that for the tetragonal configuration, the odd-even defects could potentially manipulate the electrical behavior of the COP material. The discovery provides a new direction for the targeted synthesis of semiconducting and conducting materials by tuning the inherent structure of materials, which is entirely different from the chemical doping method yielding metal-free conducting materials.

Metropolis Monte Carlo sampling in the semi-grand canonical ensemble with empirical potentials is used to predict equilibrium ordered structures and segregation properties of small icosahedral Au–Pd nanoclusters and helical nanowire segments over the whole range of compositions at low temperatures. The cases of free-standing clusters and wires are compared with the same systems encapsulated in carbon nanotubes. A number of chemically ordered structures and segregation states are identified and found to be consistent with the same interplay between size mismatch, mixing enthalpy and surface energies of elemental metals which determines the thermodynamic equilibrium of binary metal alloys. Encapsulation has the effect of modifying the surface energies of nanoclusters and wires, with considerable consequences on their thermodynamic states, although the metal–graphite interaction strength is low as compared with the metal cohesive energy and the carbon–carbon binding energy.

An effective non-metal (N) and non-transition metal (Sb) passivated co-doping approach is proposed to improve the photoelectochemical performance of rutile TiO2 for water-splitting by using first-principles calculations. It is found that the band edges of N + Sb co-doped TiO2 match with the redox potentials of water, and a narrow band gap (2.0 eV) is achieved for enhanced visible light absorption. The compensated donor (Sb) and acceptor (N) pairs could prevent the recombination of photo-generated electron-hole pairs. In addition, the N + Sb defect pairs tend to bind with each other, which could enhance the stability and N concentration of the system.