 OK, da se vse. Zato pa se počnem, da se prihodimo na tribole, da je zelo, da so prihodili, tribole je zelo, da se inožite vse, da se je rejtivne vse, da je naredila vse, da je zelo prihodila, kaj je način, da je zelo prihodila, da je zelo prihodila, je zelo vrčak. Počnem, da ste sečni, da se v 50-jih, kako je bolj in tabo izgleda za najbolj koncept vajne zvršenje, ne vsega vzvečenja vzvečenja je zelo vzvečenja in vzvečenja pa vzvečenja in vzvečenja in tribolega. Vseč na zašličenju vsečke tečnice, ki so atomeni posebnevši mikroskopi, z namely, da je bolj izgleda na odpravljenje, ta je z vsečkej uročno zbočnji, ko je z vsečkih uročna resolut nekaj. Protočno nanov technologicale, mikro in nanomekanika systems, slj hearts. Sofer serious problem of addition and friction due to the high surface to volume ratio, and very importantly the energy saving. The friction and well results in massive economic and environmental costs. So virtually every nation has realized that it cannot afford to overlook the advantages in resorcije in trivoložije. Tukaj je pravda za energijegi in karstvom. Zvukaj, da je tudi 21% energijegi in karstvom izgleda, da je vse karstvom. Vse karstvom je vsega. If you consider the large number of cars that are in the world today, you can understand that just 10% of the friction reduction in every car engine will produce very consistent fuel savings and reduction of carbon dioxide emissions. Technologi, ki so vznikovati, are based on materials. Liquid lubricants, constitutivne base oil, where lubricants additives, molecules, compounds, are included. Solid lubricant powders, like molydron disulfide and graphene graphite, and coatings made of hard materials, like diamond-like carbon, that can virtually reduce friction and wear of every surface on which they are deposited. The functionality of all these materials is deeply affected by surface chemistry. So it's very important to... So first principle calculation of a very important tool to investigate the intrinsic interfacial properties and also to quantify them. We defined a computational protocol to calculate the work of adhesion between two surfaces in contact by means of first principle calculation. This is simply obtained as the difference between the interfacial energy, the interface is defined as a system constitutiva of two slabs in contact, and the sum of the energies of the two separated surfaces. By calculating this adhesion energy as a function of the relative lateral position of the two surfaces, we obtained the potential energy surface that describes the variation of the adhesion energy during sliding. And by selecting symmetry direction, we can obtain the potential profile along that direction and by derivative the frictional forces, and we defined the ideal shear strength as the minimum force that represents the resistance to sliding, that represents the static friction force of that interface, and divided by area gives the ideal shear strength of that interface, which represents the maximum resistance to sliding. So thanks to the MAX project, we could implement this computational protocol as a workflow based on the AIDA platform that allows to obtain these intrinsic interfacial properties automatically for a large number of materials. And the workflow that we implemented is thought for non-specialized users, so a limited number of input parameters are required, and most of the computational choices are made within the workflow, in the test that are carried out automatically. And the workflow is composed by four units. In the first one, the bulk properties are calculated, so the theoretical lattice parameter is obtained, as well as the optimal k-poj density for that system. In the second unit, the surface is constructed, and the optimized surface structure is calculated, as well as the surface energy. The third unit is dedicated to the interface, which is optimized, and the potential energy surface is obtained, calculating the adhesion for different lateral positions. And finally, calculating the interaction energy of the two surfaces for different positions. And finally, the tribological properties, intrinsic of that solid interfaces are obtained, that are the adhesion energy, which corresponds to the PES absolute minimum, and the ideal shear strength, which as I said is the maximum resistance to sliding offered by that solid interface. Here you can see a representation of the potential energy surface calculated, for example, for the aluminum 111 interface, which presents the symmetry of an hexagonal lattice. Here you can see the potential profile along the x-direction, this 101-direction, and this is the potential profile along the y-direction. Of course, the system will not follow in a straightforward way these directions, because the path that has the highest statistical weight is the minimum energy path that connects the PES minima passing through the saddle point. So we implemented in our workflow the zero-temperature string method that allows to identify the minimum energy path on a given potential energy surface. So this method evolves a string, a gamma path, according to the forces acting parallel to the path, because in that the perpendicular potential forces is equal to zero. And the simplest dynamics is given by this equation where v is the velocity perpendicular to the path, because the velocity along the path is irrelevant and it simply describes the motions of the points of the path along the path. So for the same reasons, it is also the parameterization chosen to describe the path can be chosen with freedom, and also in a simple way. And so by solving an ordinary differential equation, the motion of the path toward the minimum energy path is described and so the final path is obtained. We have collected some preliminary results for FCC, BCC, crystalline structure. Here I show you, for example, the outputs that are collected from the workflow in a database which are the theoretical lattice parameter, the optimal k-poj density, the surface energy, the adhesion and the shear strength along two symmetry paths that are optimized to the minimum energy paths along that direction. So we will use this workflow to calculate these intrinsic interfacial properties for many solid interfaces, including also the presence of adsorbates and the passivating species that can deeply affect the adhesion and the shear strength resistance to slide. And so the comparison of the data will give insight into the functionality of lubricant materials. To explain a little bit in more detail what I mean for this insight that we can gain by calculating the adhesion and shear strength, I would like to present an example based on graphene. Graphene has been recently proposed as a new emerging lubricant not only for nanoscale applications, but also at the macroscale. You can see here the measurement of the friction coefficient of steel on steel performed at Ergoni National Lab in dry conditions. And when some droplets of this ethanol solution containing graphene flakes has been applied at the sliding contact. You can see that the friction is reduced by 5, 6 times and the wear rates decreased by 4 order of mantitudes. So these are very interesting results that attracted the interest of the tribology community to identify the microscopic mechanism that provides lubricity when graphene flakes are present. And a fourth explanation was proposed by the group of Mauseler who performed classical molecular dynamic simulations and suggested that the lubricating properties of graphene are related to a mechanical action basically due to the load carry capacity of the graphene layer that reduces the penetration depth of the tip, reducing the friction. And when the layer is ruptured, the substance friction is recovered and the lubricating properties are lost. This explanation, however, doesn't take into account the chemical interactions and in particular it doesn't fully explain the Raman spectra recorded after the tribological test that show that the low friction regime are observed when graphene is present in the wear tracks, even very defective graphene and while the high friction regime is obtained when graphene is removed from the wear track, not just ruptured. Indeed, we consider that the lubricating property of graphene may be related to a chemical effect due to surface passivation and the negative effect of load could be that of peeling off graphene and that reduces the coverage of the surface by graphene. We investigated these hypotheses by means of first, popularized density functional theory calculations. We used different same correlation functional, also including the van de Waas interaction. In order to minimize the mismatch between the graphene lattice and the 110 surface of iron which we considered, we rotated the graphene layer with respect to the surface and used this rectangular cell. And we calculated the binding energy of graphene on this substrate which is rather high, 0.9 javol square meter and that indicates that graphene can be solved on iron which is in agreement with experimental spectra that reveal an idealization of the pi orbital of graphene with the 3D states of iron which are not fully occupied. We also consider rebones where the reactive edge enhance the adhesion so this edge anchor the flakes on the surface and then we constructed the interface. First of all, by mating two iron surfaces and that's obtaining the adhesion which equals twice the surface energy as expected. Then we consider an interface composed by a clean iron surface fully covered iron surface by graphene and we calculated the adhesion which is 80% reduced by the clean surface with respect to the clean situation and in a fully passivated interface we obtain almost 90% decrease of the adhesion. Iron surface is covered by graphene become almost inert and present very low adhesion and very low adhesion. This is clearly evident if we plot the adhesion energy as a function of the surface separation in the blue core, the blue core represents the clean interface and the black one is a fully passivated interface by graphene. This core is very similar to the red core which is obtained for the belayer graphene so you can see that the surface passivation by graphene changes the nature of the surface-surface interaction from chemical to physical. This produces a nine-me impact on the resistance to sliding of the system. As you can see by comparing the potential energy surface obtained for iron on iron to that obtained for a fully passivated interface. Not only the symmetry of the two potential energy surface changes but most importantly the corrugation. We have used two different scales here and the minimum energy paths the corrugation of the minimum energy paths is reported here and from which we obtained the shear strength for the two interfaces which are very different almost two orders of magnitude. The fact of graphene is to reduce by almost two orders of magnitude the resistance to sliding of iron. These properties affect the macroscopic properties such as the friction coefficient. Adhesion and chemical interaction really have a high impact on what is measured macroscopically. These calculations seem to confirm that the passivation plays a very important role. We verified these hypotheses by experiments in our institute. We can also perform tribological experiments by means of ball on disk trebometer and we compared the friction coefficient of graphene on iron and on bronze. When the ethanol solution containing graphene flakes was used for a ball or steel on an iron substrate we obtained this red friction coefficient which is much lower than in the case of dry condition and in the case of poor ethanol which is not stable. And the Raman spectra revealed that the graphene is present in the wear track on the iron disk. When we repeated the experiment on bronze we obtained an even lower friction coefficient with the ethanol solution containing graphene flakes. And the Raman spectra indicated that graphene is present not on the wear track not on the bronze disk but on the steel ball. Indikati, if we compare the binding energy of graphene on copper which the sample of bronze was made mostly of copper so the binding energy of graphene physics of some copper while it can be solved on iron as it's also clearly visible in the addition energy is a function of distance. So what happens is that graphene flakes attach to the ball made of steel and they cover the native part of the balls that are very reactive and are exposed during rubbing. So in both cases, in the first case the reactive part of the surfaces of the contact was on iron, on the iron disk that was covered by graphene and in the second example the ball was covered by graphene because the substrate doesn't present a very high surface reactivity. So the lubricating property of graphene are related to its ability to passivate the reactive native surfaces that are exposed during rubbing. So, in konkluzion we developed a computational protocol to calculate from force principle the adhesion and shear strength of solid surfaces. The protocol has been implemented as either workflow and now we have this software that can be used to calculate the tribological properties of solid interface in a high throughput way and knowing these intrinsic interfacial properties the knowledge of these intrinsic interfacial properties like the adhesion and the resistance to sliding is very important to get inside into the lubricating properties of materials and I have presented an example which is based on graphene that is considered a new emerging lubricant. I would like to thank the people who mostly contributed in the development of the workflow first of all Paura Restucia, Giulio Fatti and Mikael Wallock also Giacomo Laudite, professor Mauro Ferrario I would like to mention Diego Marchetto who performed the experiments and of course Tankte Max project for support and I would like to thank you for your attention.