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Drawing on the resource-based view of the firm, and counter to the mainstream literature, we propose and empirically show that two knowledge resources can be substitutive (rather than complementary...

Purpose The relationship between motivation at work and internal knowledge transfers (IKTs) is an important topic in the knowledge management literature, but evidence on the topic is contradictory. This study aims to analyze the mediating role of transactive memory systems (TMSs) in this relationship. Design/methodology/approach Data were obtained from 208 military knowledge workers (analysts) from a large European army. Findings The results indicate that intrinsic and identified motivation positively affect IKTs, although fully mediated by the TMS. Introjected motivation, in contrast, has only a slightly significant direct influence and external motivation has no significant effect. As individual motivation is insufficient to speed up knowledge transfer, this paper proposes the solution of implementing a TMS, which generates trust and improves coordination among group members. Originality/value This study’s originality stems from both its context and the problem tackled. The context analyzed is the military, a group that has received very little attention in the field of management and business. Individual motivation in job performance has also received little study in a military context and even less research has related individual motivation to IKTs. To supplement the scarcity of existing studies and resolve the possible difficulties identified concerning IKT in the military, this study proposes to analyze the mediating effect of a TMS on the relationship between individual motivation to perform one’s job and IKTs.

The extant literature highlights that environmental conditions, during the creation phase, imprint on a start-up's survival and growth. However, there are few studies that explore the composite nature of a founding team's capabilities and networks, developed within this phase, and the contribution made to future performance. This paper uses the distinctive context of university spin-offs, where early stage ventures are fostered by institutional interventions, to analyse the influence that the capabilities and networks of a founding team, at incorporation, have upon the future performance of the spin-off. Based on data from 181 university spin-offs, this paper empirically demonstrates that the entrepreneurial capabilities of a founding team, augmented during the ‘creation’ phase, have a positive influence on the performance of a spin-off during the ‘growth’ phase, and that the networks of a founding team indirectly affect a spin-off's performance through the enhancement of a team's entrepreneurial capabilities.

Drawing on a dynamic capabilities perspective and a resource-based view, this article analyzes the relationship between absorptive capacity and corporate entrepreneurship, and their combined e ect on organizations’ performance. It contributes to the literature by dissociating the dimensions of absorptive capacity (potential and realized) and corporate entrepreneurship (innovativeness, proactiveness, new business venturing, and self-renewal). A quantitative study was performed with data gathered by personal interviews, using a structured questionnaire. The theoretical model was estimated through a structural equation model, using a sample of 168 Spanish firms. The results show that proactiveness positively influences innovativeness and that both proactiveness and innovativeness have a positive influence on potential and realized absorptive capacity. A significant positive relationship also exists between potential and realized absorptive capacity. Furthermore, realized absorptive capacity positively influences new business venturing and self-renewal. Finally, proactiveness and new business venturing directly and positively influence organizational performance, but not innovativeness and self-renewal. The study demonstrates that entrepreneurs must be able to enhance potential and realize absorptive capacities at the same time in order to improve the end performance of their corporate entrepreneurial projects. Both absorptive capacities are strongly related to corporate entrepreneurial activities and have a strong influence on firms’ performance., Ministry of Science and Innovation under Grant ECO2013-47027-P and ECO2017-88222-P, Regional Government of Andalusia under Grant P11-SEJ-7294 and P11-SEJ-7988 and the European Union (FEDER Funds)

Quality management (QM) affects many variables related to marketing. Persuaded by the numerous benefits and competitive potential of QM, many firms have decided to implement QM programs. The study examines how the fit between industrial environment characteristics and QM practices impacts financial, operational and employee performance. To test our hypotheses, we surveyed a sample of 273 managers. The findings suggest that the results of implementing QM practices depend on the degree on internationalization of the industrial environment, as well as on the existing level of competence. Findings offer implications for marketing theory and practice as well as for strategic management and QM.

Absorptive capacity is an ability firms should develop if they wish to adapt to changes in an increasingly competitive and changing environment and to achieve and sustain competitive advantage. Despite the increase in literature on absorptive capacity, some ambiguity remains in determining the dimensions that shape the construct. Thus, no measurement instrument can be adapted to these dimensions. The aim of this paper is to contribute to the literature on absorptive capacity by using a resource-based view to present an alternative measurement instrument for absorptive capacity. This instrument differentiates between the phases of acquisition, assimilation, transformation and exploitation of knowledge, as well as between the two dimensions of absorptive capacity (potential and realized), to reduce the problem of measuring and identifying the dimensions that shape this important construct. The instrument’s validity and reliability are guaranteed and have been tested using data from 168 Spanish organizations.

This article analyzes outsourcing from a knowledge-based perspective. We investigate how knowledge as an organizational resource and the capabilities to manage this knowledge affect the benefits of outsourcing. Our results indicate that the nature of the knowledge of the outsourced activity affects the success of outsourcing. We also analyze the way in which collaborative know-how (as a knowledge resource) and learning capability (as an organizational capability) affect outsourcing benefits. We then test the validity of this hypothesis by surveying organizations from the service sector. The results of the empirical study provide strong support for our assertion that knowledge management affects the results of outsourcing decisions.

Ab initio density functional theory simulations are performed for carbon monoxide oxidation at gold nano-catalysts, focussing in the influence of multiply-adsorbed CO on the reaction mechanisms. Both small nano-clusters (Au 4 , Au 5 ) and a model of gold nanoparticle edge sites are used. For Au 5 , CO displaces pre-adsorbed molecular O 2 , although oxygen remains close and eventually reacts with CO forming OCOO − radicals. Interaction with neighboring co-adsorbed CO then directly forms two CO 2 molecules. Similar results are found for gold nanoparticles, although much weaker O 2 binding results in smaller activity. Cooperation of several co-adsorbed entities is therefore an important issue on the mechanisms of oxidation reactions on gold in the low temperature regime.

The chemical properties of small gold clusters Aun with n up to 10 atoms were investigated using density functional theory (DFT). These clusters have planar structures, and we analyzed the effects of the planarity on the chemistry of the clusters. Using atomic hydrogen as a chemical probe, we found a strong site dependence of the reactivity: the H atoms preferentially react at regions on the rim of the planar cluster. A strong directionality of the bonds formed was also observed. Bonds in directions contained in the plane of the Au cluster are preferred, and bonds along the direction perpendicular to the cluster plane are generally unfavorable. These features are rationalized in terms of the spatial distribution of the frontier orbitals and the Fukui functions. We also found a strong odd−even oscillation of the reactivity with cluster size, which can be explained from the occupation of the frontier orbitals. Finally, we explored the influence of the site-dependence reactivity and the directionality of th...

This paper analyzes the relationship between quality management (QM) and knowledge transfers. The study of QM was tackled by analyzing the degree of implementation of the different practices that compose it. Hypotheses are developed on the relationship between some QM practices and knowledge transfers. Both the proposed model and the hypotheses were tested on a sample of 197 Spanish firms. The results confirm the importance of the different QM practices on internal and external knowledge transfers.

In this paper an analysis is made of the relation between the general and specific topics of management and the Six Sigma approach. This study has led us to suggest that there is a great deal of similarity in the prescriptions of Six Sigma and management theory. Furthermore, we analyze various processes and practices of Six Sigma that help towards an improvement in organizational effectiveness. The conclusion that can be drawn from this research is that, in order to reach its goals, the implementation of a Six Sigma program needs to change the way in which employees behave at work. Six Sigma must alter how people actually behave at work and, to this end, various behavioral and work processes are key to achieving these aspirations. Implications are discussed with regard to performance management processes in organizations.

The past decade has witnessed an increase of interest in flexibility, which bestows on a firm the ability to respond promptly to market opportunities and changing technologies. The development of capabilities to be flexible rests on the mandate of top management, helps firms manage environmental uncertainty, and tends to enhance firm performance. This research paper aims to establish an analytical approximation that considers how the determinants of manufacturing flexibility at the system level affect the desired strategic change in organizations, as well as subsequent performance. We propose the hypotheses that both environmental factors and internal resources affect flexibility, this latter aspect influencing the organization's performance. The problems that stem from measuring manufacturing flexibility in terms of fit were also analyzed. In order to do this, we have made a wide-ranging trans-national study, within the framework of the European Union, using data from 403 European firms. The Structural Equation Model (SEM) technique has been used to contrast the hypotheses. The results show that manufacturing flexibility at system level can be a critical factor in the process of strategic change, which means that it can have an impact on the desirability of strategic change or on the more specific strategic fit.

We present a small review of recent density-functional-theory (DFT) studies of the reactivity towards CO oxidation of supported Au nano-particles. The possible structure of the periphery of the interface between a Au particle and an oxide support is discussed. A certain structure, in which low coordinated Au atoms are overhanging the support without binding directly to the oxide atoms, is argued to be prototypical of medium-sized Au particles. This structure is shown to be particularly active both at the edges and at the corners of Au particles. Examples from the literature of Au systems supported on MgO(1 0 0) and rutile-TiO2(1 1 0) are reviewed and new data are given for the reactivity of facet, edge, and corner sites of a Au34 cluster supported on MgO(1 0 0). On the non-reducible oxide support, MgO(1 0 0), the CO oxidation is found to occur via CO adsorption to the Au particles and subsequent CO-promoted O2 capture and formation of a CO·O2 reaction intermediate complex. On the reducible oxide support, TiO2(1 1 0), the O2 is found to adsorb independently of the CO. However, on this support, the reaction still proceeds via CO·O2 formation rather than via O2 dissociation.

Several issues concerning the activity of the magical Au20 cluster are addressed with the help of Density Functional Theory (DFT) simulations. First, the cluster is found to be extremely robust against distortions when supported at an oxide (MgO) surface, keeping its tetrahedral shape. Second, the activity toward CO oxidation is studied as a function of the cluster charge state. Whereas the neutral cluster is found to be only moderately active, the anion becomes extremely active, because of the presence of a weakly bound unpaired electron. The attempt to induce cluster charging upon attachment to a charged surface F+-center was unsuccessful, with a cluster only slightly more active than the unsupported, neutral one. Finally, some initial steps towards the rational design of active catalysts were taken by the study of the effect of having different impurities. Promising results are obtained by the addition of an extra Na atom, which preferentially adsorbs inside the tetrahedron. Two competing isomers with an endohedral Na atom within a Au20 cage are found, and both of them are very active.

The adequate management of knowledge transfers is considered a key factor for improving the organization’s performance and long-term survival. The relationship between the principles and practices considered appropriate in literature on quality management, as well as on knowledge management, do, to a great extent, coincide. This paper studies the importance that implementing both TQM and the ISO 9000 certification has on knowledge transfers. We, firstly, analyse the relevance of both on knowledge transferability. Secondly, we study the link between their implementation and knowledge transfers both among the firm’s groups and from customers and suppliers. The hypotheses proposed have been tested using a sample of 215 Spanish firms. The results confirm TQM’s importance regarding knowledge transfers. On the other hand, the relevance of implementing the ISO 9000 standards has not been confirmed, though it does have a positive impact on the organization’s knowledge transferability.

Many organizations are adopting quality and innovation as practices that allow them to achieve competitive advantage owing to an increase in competitiveness. The goal of this paper is to examine whether quality can be regarded as a resource that sets up the necessary bases for implementing innovations in organizations. First, the concepts of quality and innovation are determined, so that we can analyse how they relate to each other. Later on, the different contributions existing that deal with the relationship between quality and innovation are revised. In the second part of the research, we formulate and verify some hypotheses, which are empirically tested using a sample of bank employees in several financial entities. Results allow us to establish that quality relates to innovation both directly and indirectly, in the latter case through employees’ satisfaction.

In the study of fullerene-like structures, some of the more interesting systems are the inorganic cages, made of MoS 2 (usually named inorganic fullerenes), which have many important potential applications as lubricant and catalysts. In the present work, we report calculations for structural models of closed cage of inorganic fullerene-like structures for MoS 2 system. Three cage shapes were found to be the most stable: triangular pyramid, octahedron and dodecahedron. High resolution TEM images of MoS 2 cages structures were calculated to be compared with experimental data. Some examples of triangular pyramid and polyhedron in experimental MoS 2 samples are presented.

A new suggestion for the structure of the Au substrate underlying self-assembled monolayers (SAM) made of thiols is presented on the basis of density functional theory results for methylthiolate (–SCH3) adsorption on Au(1 1 1). It is found that by introducing vacancy defects on the substrate, the adsorption of SCH3 is stabilized by about 0.8 eV with respect to the perfect Au(1 1 1) surface. As this overcomes the vacancy formation energy (≈0.6 eV), a net driving force exists leading to an adsorbate-induced reconstruction, that enhances adsorption at defected Au(1 1 1). A comparison of results at high and low SCH3 coverage provides further insight into which specific gold vacancy sites enhance the adsorption energy of the SCH3 molecule.

Clusters with closed electronic shells are highly stable, and this is a robust property with far-reaching implications for cluster abundance, cluster shapes, dynamical response to electric fields and cluster dissociation. Clusters with closed shells are also good candidates for the synthesis of novel materials. The density functional formalism is currently used to investigate the self-assembling of metallic clusters to yield cluster solids. A high intrinsic stability is not the only requirement for expecting a successful assembling, and we investigate additional conditions by performing computer simulations for selected examples. The study of the assembling of hydrogen-doped icosahedral aluminium clusters shows that an optimized relative orientation of each cluster unit with respect to all its neighbour clusters becomes a favourable condition. The analysis of the clustering effects observed in crystalline alloys formed by Pb and alkali metals (tetrahedral Pb4 clusters surrounded by the alkali cations form in those alloys) provides further insight: coating passivates the clusters and helps to stabilize the assembled material.

Producción Científica, Ab initio density functional simulations have been performed to study the adsorption of propene on partially oxidized silver surfaces and its interaction with surface oxygen. Two different adsorption conformations for propene are studied, with the molecule either intact or forming an Ag–C3H6–O oxymetallacycle (OMC) intermediate. Then, pathways for propene oxide, acrolein and propanone formation have been studied in detail, providing insight into the selectivity of the surfaces. We find that formation of acrolein must necessarily take place from OMC intermediates, requiring at least two neighbouring reactive surface oxygen anions. This suggests a strong relationship between the concentration of surface oxygen and the selectivity of these surfaces., Ministerio de Ciencia e Innovación (Proyect MAT2008-06483-C03-01 and MAT 2011-22781), Junta de Castilla y León (programa de apoyo a proyectos de investigación - Ref. A158A11-2

Density functional theory is used to investigate the assembling of metallic clusters to yield stable or metastable cluster solids. Motivated by the observed high stability of the Al13H cluster, which has a substantial highest occupied and lowest unoccupied molecular orbitals (HOMO–LUMO) gap, we have modeled the assembling of those clusters. For a favorable relative orientation of each cluster with respect to all its neighbors, a cluster solid is predicted and its structure appears to be stable at least up to 150 K, which is the highest temperature in our simulations. We have also studied the chemical bonding in the stoichiometric solid alloys PbA, where A is one of the alkali elements Na, K, Rb, or Cs. Those crystals exist in an ordered phase formed by tetrahedral Pb4 clusters surrounded by the alkali atoms. The study of this family of natural cluster compounds reveals the coating role played by the cations, providing further insight into the favorable conditions required for the formation of cluster solids. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001

The electronic and atomic structure of Al13H has been studied using Density Functional Theory. Al13H has closed electronic shells. This makes the cluster very stable and suggests that it could be a candidate to form cluster assembled solids. The interaction between two Al13H clusters was analyzed and we found that the two units preserve their identities in the dimer. A cubic-like solid phase assembled from Al13H units was then modeled. In that solid the clusters retain much of their identity. Molecular dynamics runs show that the structure of the assembled solid is stable at least up to 150 K. A favorable relative orientation of the clusters with respect to their neighbors is critical for the stability of that solid.

Ab initio total energy calculations are used to simulate the assembling of equiatomic APb alloys (A=Li, Na, K) from A4Pb4 free clusters in order to investigate the remarkable stability of tetrahedral Pb4 units in some of these solid and liquid alloys. Starting from a greatly expanded array of eight Na4Pb4 clusters per unit cell, the NaPb solid alloy was assembled by shrinking the unit cell and allowing full atomic relaxation at each stage. The evolution of cluster properties as the clusters are drawn together into the solid was studied. Charged (Pb4)4− tetrahedral units were found to dominate the structural and electronic properties, being very robust and quite insensitive to their alkali environment. Trends with the choice of alkali were also investigated, showing that the stability of the (Pb4)4− units decreases as we progress from K to Li and leads to their absence in the LiPb alloy in accordance with experiment. The critical factor for the survival of the units proved to be the distance between them, which was determined by the atomic size of the alkali. The effect of pressure on the systems was also considered.

Ab initio total energy calculations are used to investigate the structural trends of equiatomic solid APb alloys (A=Li, Na, K). The NaPb bulk structure was assembled starting from a greatly expanded array of eight Na 4 Pb 4 clusters per unit cell. The clusters were drawn together by shrinking the unit cell in stages and allowing full atomic relaxation at each stage. Charged Pb 4 tetrahedral units dominate the structural and electronic properties and these units are remarkably robust and insensitive to their alkali environment. The stability of the Pb 4 units diminishes as we progress from K to Li and leads to their absence in the LiPb alloy in accordance with experiment. The distance between Pb 4 units seems to be the critical factor responsible for the structural trends and the atomic size of the alkali determines this.

Ab initio density functional calculations for mixed clusters of Pb and alkali elements demonstrate the high stability of the octet clusters A 4 Pb in the case of light alkali metals, that is for A=Li or Na. This justifies the observed anomalies at the composition of 20% Pb in the liquid alloys of Pb with Li and Na. The calculations also show the high stability of the Zintl clusters A 4 Pb 4 , which explains the crystalline structure of the equiatomic solid compounds of Pb with Na, K, Rb and Cs, and the persistence of the Zintl complexes in the melt. The absence of Zintl clustering in the Li alloys is due to an atomic size effect.

We have performed ab initio total-energy pseudopotential calculations on neutral and negatively charged Snn and Pbn (n = 3 − 10) clusters. The lowest energy structures have been determined for all clusters, and the stabilities of neutral clusters were investigated by comparing their evaporation energies and stability functions. Clusters with n = 7, 10 were found to be most stable while the clusters with n = 8 and Pb5 were much less stable, in agreement with features of the observed mass spectra. Calculations on Sn−n and Pb−n show that both atomic and electronic structures of a neutral cluster change substantially upon charging. The densities of states of Sn−n clusters reproduce the main features of the experimental photoelectron spectra. The agreement is poorer for Pb−n clusters where the calculations underestimate the separation between energy levels which we think is due to the larger spin-orbit splitting in Pb, which was neglected in the calculations. We found that the differences between Sn and Pb clusters cannot be completely addressed without a more complete accounting of relativistic effects. The electron affinities of Snn and Pbn clusters have also been calculated and the results agree fairly well with experimental values. Finally we considered Sn2−4 and Pb2−4 clusters and related the results to the formation of Zintl anions in liquid alkali-Sn and alkali-Pb alloys.

Model silver nanocatalysts between 9 and 23 nm in size were prepared by size-selected cluster deposition from a free cluster beam on amorphous alumina films and their size-dependent catalytic performance studied in the partial oxidation of propylene under realistic reaction conditions. Smaller clusters preferentially produced acrolein, while the 23 nm particles were considerably more selective towards the formation of propylene oxide, at reaction rates far exceeding those previously reported for larger silver particles. The activity of clusters dropped significantly with increasing particle size. First-principle calculations, of the activation energies for oxygen adsorption and its dissociation, at variable surface coverage yielded surface energies which resulted in particle shapes resembling the experimentally observed shapes of partially oxidized silver clusters. The calculated activation barriers for propylene oxide and acrolein formation on various facets and on the edges of the nanoparticles provided detailed information about the energetics of the competing reaction pathways. The size- and corresponding morphology dependent theoretical activity and selectivity are in good accord with experimental observations.

This article analyzes outsourcing from a knowledge-based perspective. We investigate how knowledge as an organizational resource and the capabilities to manage this knowledge affect the benefits of outsourcing. Our results indicate that the nature of the knowledge of the outsourced activity affects the success of outsourcing. We also analyze the way in which collaborative knowhow (as a knowledge resource) and learning capability (as an organizational capability) affect outsourcing benefits. We then test the validity of this hypothesis by surveying organizations from the service sector. The results of the empirical study provide strong support for our assertion that knowledge management affects the results of outsourcing decisions.

The interest in hydrogen goes across disciplines. Hydrogen is a molecular gas, but many interesting scientific aspects and most of the technological possibilities of this material come from condensed hydrogen phases, either as small or large molecular clusters, as a liquid, or adsorbed on the surface of materials. Recent work on these areas is reviewed. As H 2 is a very stable molecule in which the two electrons form a closed electronic shell, (H 2 ) N clusters have some similarities with the clusters of the inert gases. By irradiating molecular beams of large deuterium clusters with an intense femtosecond laser, the Coulomb explosion of the clusters has been induced, and collisions between the flying deuterium nuclei have achieved nuclear fusion. Here, we analyze the first stages of this interesting process, that is, the dynamical evolution of the deuterium clusters after absorbing energy from the laser. Fragmentation of the cluster, or ionization followed by Coulomb explosion can occur depending on the size of the cluster and the frequency and intensity of the laser field. Motivated by the firm expectations that hydrogen will be used in the near future as a fuel in electric cars, a strong effort is now dedicated in many laboratories to find good hydrogen storage materials. Theoretical work has focused on graphitic materials with a large specific surface area. The results of the simulations indicate that the hydrogen storage can be optimized using porous carbon materials with pore sizes of about 0.6 nm and doped with impurities like lithium. Hydrogen can also be used to probe the local reactivity of clusters. This property is illustrated here for the family of planar gold clusters, highly relevant because of the catalytic activity shown by those clusters.

Udgivelsesdato: 16.01.09 Epoxidation made easy: Subnanometer gold clusters immobilized on amorphous alumina result in a highly active and selective catalyst for propene epoxidation. The highest selectivity is found for gas mixtures involving oxygen and water, thus avoiding the use of hydrogen. Ab initio DFT calculations are used to identify key reaction intermediates and reaction pathways. The results confirm the high catalyst activity owing to the formation of propene oxide metallacycles. Al green, Au yellow, O red, and C gray.

To determine whether the number of optimally controlled hypertensive patients is higher using self-measurement of blood pressure at home and ambulatory monitoring, compared to using conventional blood pressure measurements at the doctor's office.An observational, cross-sectional, multicentre, descriptive study of a random sample of 237 primary health care patients, known to be hypertensive, from Badajoz (Spain). Blood pressure was measured at the doctor's office and by self-measurement at home. Those patients showing good control by self-measurement were subjected to 24-hour ambulatory monitoring. Optimal control was understood as blood pressure140/90 mm Hg when measured at the doctor's office, and135/85 mm Hg when self-measured at home and by daytime ambulatory monitoring.Mean systolic/diastolic measurements at the doctor's office and by self-measurement were 145.6/83.9 and 134.0/78.7 mm Hg, respectively (p0.000). In the population optimally controlled by self-measurement and who subsequently received ambulatory monitoring, the mean blood pressure was 121.8/73.4 and 125.6/76.2 mm Hg, respectively (p = 0.002; p0.000). When measured at the doctor's office blood pressure was controlled in about 29.5% (95% CI 23.7-35.3%) of patients, in 38% when self-measured (95% CI 31.4-44.2%; p0.000), and in 24.5% when it was confirmed through ambulatory monitoring (95% CI 15.4-33.6%). Sensitivity and positive predictive values of the office measurements for the detection of patients who were well-controlled by self-measurement were 50% and 64.3%, respectively, and 53.4% and 73.8% as regards ambulatory monitoring.A higher level of control is achieved with self-measurement at home not confirmed by ambulatory monitoring. Therefore, the white coat effect does not seem to influence the percentage of well-controlled patients detected at the doctor's office. Office blood pressure does not appear to be useful in distinguishing which individual patients are optimally controlled.

The interaction potential of a $\mathrm{Li}$ atom with a graphene layer is calculated using the local density approximation to the density functional theory. Two configurations corresponding to different separations between $\mathrm{Li}$ in neighboring supercells were considered to determine the effect of $\mathrm{Li}\text{\ensuremath{-}}\mathrm{Li}$ interaction on the binding of $\mathrm{Li}$ to graphene. The equilibrium position of $\mathrm{Li}$ is not affected by the $\mathrm{Li}\text{\ensuremath{-}}\mathrm{Li}$ interaction and remains the same in both cases. It is equal to $3.1\phantom{\rule{0.3em}{0ex}}\mathrm{a.u.}$ above graphene with the $\mathrm{Li}$ at the center of a hexagonal ring formed by the carbon atoms. However, the binding energies differ substantially in the two configurations. The binding energy of $\mathrm{Li}$ is $0.934\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in configuration A when the $\mathrm{Li}\text{\ensuremath{-}}\mathrm{Li}$ separation in adjacent supercells is $9.22\phantom{\rule{0.3em}{0ex}}\mathrm{a.u.}$ The binding energy is $1.598\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in configuration B corresponding to a separation $18.45\phantom{\rule{0.3em}{0ex}}\mathrm{a.u.}$ between adjacent $\mathrm{Li}$ atoms. There is substantial charge transfer from both lithium and carbon atoms (including those that do not surround the lithium) to a region between the $\mathrm{Li}$ and graphene at the minimum energy configuration. The interaction potential for both configurations can be fitted to a sum of a screened Yukawa potential and a linear superposition of power-law functions of type ${r}^{\ensuremath{-}n}$, where $n$ is an integer. The density functional theory underestimates the attractive contribution of dispersion forces for large separations. The attractive interaction potential calculated for $\mathrm{Li}$ positions much greater than the equilibrium distance from graphene may therefore need to be corrected.

Using scanning tunneling microscopy we have studied the nucleation and growth of unidirectional molecular rows upon adsorption of the amino acid cysteine onto the anisotropic Au(110)-(1 x 2) surface under ultrahigh vacuum conditions. By modeling a large variety of possible molecular adsorption geometries using density-functional theory calculations, we find that in the optimum, lowest energy configuration, no significant intermolecular interactions exist along the growth direction. Instead the driving force for formation of the unidirectional molecular rows is an adsorbate-induced surface rearrangement, providing favorable adsorption sites for the molecules.

The properties of reduced rutile TiO2(110) surfaces, as well as the adsorption, diffusion, and dissociation of molecular oxygen are investigated by means of density functional theory. The O2 molecule is found to bind strongly to bridging oxygen vacancies, attaining a molecular state with an expanded O-O bond of 1.44 A. The molecular oxygen also binds (with somewhat shortened bond lengths) to the fivefold coordinated Ti atoms in the troughs between the bridging oxygen rows, but only when vacancies are present somewhere in the surface. In all cases, the magnetic moment of O2 is lost upon adsorption. The expanded bond lengths reveal together with inspection of electron density and electronic density of state plots that charging of the adsorbed molecular oxygen is of key importance in forming the adsorption bond. The processes of O2 diffusion from a vacancy to a trough and O2 dissociation at a vacancy are both hindered by relative large barriers. However, we find that the presence of neighboring vacancies can strongly affect the ability of O2 to dissociate. The implications of this in connection with diffusion of the bridging oxygen vacancies are discussed.

Density functional theory calculations are performed for the adsorption of O2, coadsorption of CO, and the CO+O2 reaction at the interfacial perimeter of nanoparticles supported by rutile TiO2(110). Both stoichiometric and reduced TiO2 surfaces are considered, with various relative arrangements of the supported Au particles with respect to the substrate vacancies. Rather stable binding configurations are found for the O2 adsorbed either at the trough Ti atoms or leaning against the Au particles. The presence of a supported Au particle strongly stabilizes the adsorption of O2. A sizable electronic charge transfer from the Au to the O2 is found together with a concomitant electronic polarization of the support meaning that the substrate is mediating the charge transfer. The O2 attains two different charge states, with either one or two surplus electrons depending on the precise O2 adsorption site at or in front of the Au particle. From the least charged state, the O2 can react with CO adsorbed at the edge sites of the Au particles leading to the formation of CO2 with very low (approximately 0.15 eV) energy barriers.

We present a density-functional-theory (DFT) study of the reactivity towards CO oxidation of Au nanoparticles supported by MgO(100). We model two geometrical aspects of the Au particles, the low index facets of the Au particles, and the Au-MgO interface boundary. The precise structure of the interface boundary depends on the size of the Au particles, and different models with either small or large Au-MgO contact angles are introduced. For all Au systems, we find that the CO oxidation reaction proceeds via CO adsorption, trapping of ${\mathrm{O}}_{2},$ leading to the formation of a metastable $\mathrm{CO}\ensuremath{\cdot}{\mathrm{O}}_{2}$ reaction intermediate, which dissociates into ${\mathrm{CO}}_{2}$ and adsorbed atomic oxygen. The atomic oxygen reacts directly with gas phase CO. No separate ${\mathrm{O}}_{2}$ molecular or dissociative adsorption is found to be favorable. Important differences were found in the reactivity of the various Au-MgO interface boundaries. This is explained in terms of two properties: the Au-Au coordination determining the local reactivity of the Au atoms and the presence of the MgO support that, besides providing excess electrons to the Au clusters, forms ionic bonds to the peroxo part of the $\mathrm{CO}\ensuremath{\cdot}{\mathrm{O}}_{2}$ reaction intermediate. We find that the type of interface boundary likely to be predominant for medium-sized nanoparticles provides the optimal degree of low-coordinated Au atoms in the neighborhood of the MgO support. Our DFT study therefore provides a rational for why the reactivity per site may reach a maximum at a critical particle size as has been observed experimentally for similar systems.

Density-functional theory has been used to study the CO oxidation reaction at model Au/MgO catalysts modified by either Na (an electron donor) or Cl (an electron acceptor) dopants. In agreement with experimental observations, Cl is found to act as a poison, making both the adsorption of O2 and the formation of the CO ⋅ O2 intermediate complexes that mediate the formation of CO2 on these model catalysts more difficult. The poisoning effect of Cl has a long-ranged character, reaching at least two Au sites away from the adsorbed Cl atom. On the other hand, Na is found to be a promoter, enhancing both O2 binding and CO ⋅ O2 formation. Its promotive character is, however, local, involving the formation of strong Na O bonds.

Ab initio density-functional molecular dynamics simulations were performed in order to study the melting behavior of the NaSn alloy. This alloy exhibits a phase transition at 756 K to a high-temperature solid showing rotational disorder, which has been described as an assembly of rapidly rotating Sn 4 tetrahedral clusters surrounded by mobile Na cations. Various simulation temperatures and volumes were considered in order to distinguish the features of both solid β-NaSn and plastic α-NaSn phases. The results show that the ability of Na cations to diffuse is strongly linked to the deformation of Sn 4 tetrahedra. In addition, the α-NaSn phase seems to be characterized by a sizable degree of structural disorder, with frequent breaking of the Sn 4 tetrahedral units. The influence of the volume of the simulation cell on the dynamical behavior of the alloy was found to be very important, with increasing disorder as the volume was reduced. Finally, strong correlations between structural and electronic properties were found, with increased disorder leading to more metallic behavior.

The oxidation of CO at MgO supported gold aggregates is studied by means of density functional theory calculations. In addition to serving as a structural promoter holding the gold particles, the supporting oxide also takes an active role in the bonding and activation of adsorbates bound to the gold. The oxide stabilizes a peroxolike reaction intermediate, CO O 2 , and causes steric repulsion to CO. The most reactive site at Au/MgO appears where the gold shelters the MgO thereby creating a cavity where several low-coordinated Au atoms and Mg 2 + cations from the substrate can interact simultaneously with an adsorbate.