Entanglement and Mutual Information in Molecules: Comparing Localized and Delocalized Orbitals.

The use of the mutual information (MI) as a measure of the entanglement in quantum systems has gained a consensus in recent years, even if there is an ongoing effort to distinguish the classical and quantum contributions contained therein. This quantity has been first introduced in condensed matter physics, in particular, in studies based on the density matrix renormalization group method. This method has been successfully adapted to quantum chemistry problems, opening the way to compute MI also in molecular systems.

Surface Depassivation via B-O Dative Bonds Affects the Friction Performance of B-Doped Carbon Coatings.

Boron doping of diamond-like carbon coatings has multiple effects on their tribological properties. While boron typically reduces wear in cutting applications, some B-doped coatings show poor tribological performance compared with undoped films. This is the case of the tribological tests presented in this work in which an alumina ball is placed in frictional contact with different undoped and B-doped amorphous carbon coatings in humid air.

Toward a continuum description of lubrication in highly pressurized nanometer-wide constrictions: The importance of accurate slip laws.

The Reynolds lubrication equation (RLE) is widely used to design sliding contacts in mechanical machinery. While providing an excellent description of hydrodynamic lubrication, friction in boundary lubrication regions is usually considered by empirical laws, because continuum theories are expected to fail for lubricant film heights ≪ 10 nm, especially in highly loaded tribosystems with normal pressures ≫ 0.1 GPa.

2D KBr/Graphene Heterostructures-Influence on Work Function and Friction.

The intercalation of graphene is an effective approach to modify the electronic properties of two-dimensional heterostructures for attractive phenomena and applications. In this work, we characterize the growth and surface properties of ionic KBr layers altered by graphene using ultra-high vacuum atomic force microscopy at room temperature. We observed a strong rippling of the KBr islands on Ir(111), which is induced by a specific layer reconstruction but disappears when graphene is introduced in between.

Reconstruction of a 2D layer of KBr on Ir(111) and electromechanical alteration by graphene.

A novel reconstruction of a two-dimensional layer of KBr on an Ir(111) surface is observed by high-resolution noncontact atomic force microscopy and verified by density functional theory (DFT). The observed KBr structure is oriented along the main directions of the Ir(111) surface, but forms a characteristic double-line pattern. Comprehensive calculations by DFT, taking into account the observed periodicities, resulted in a new low-energy reconstruction.

Experimental and Ab Initio Characterization of Mononuclear Molybdenum Dithiocarbamates in Lubricant Mixtures.

Molybdenum dithiocarbamates (MoDTCs) are a class of lubricant additives widely employed in automotives. Most of the studies concerning MoDTC take into account the dimeric structures because of their industrial relevance, with the mononuclear compounds usually neglected, because isolating and characterizing subgroups of MoDTC molecules are generally difficult. However, the byproducts of the synthesis of MoDTC can impact the friction reduction performance at metallic interfaces, and the effect of mononuclear MoDTC (mMoDTC) compounds in the lubrication has not been considered yet in the literature.

Adsorption and Dissociation of Ni(acac) on Iron by Ab Initio Calculations.

Among metal β-diketonates, nickel acetylacetonate (Ni(acac)) has been widely employed as a precursor for many chemical structures, due to its catalytic properties. Here, we investigate, by means of density functional theory (DFT) calculations, the adsorption and dissociation of this complex: after an evaluation of the structural and electronic properties of Ni(acac), a comparison between different dissociation patterns reveals that the most favorable pattern for the complex adsorbed on iron is different from the one suggested by considering the strength of the bonds in the isolated complex and an attempt to generalize this dissociation model is made in this work. Moreover, the most favorable adsorption configurations turned out to be a positioning of the nickel atom along with an positioning of the oxygen atoms of Ni(acac), while a positioning is the most favorable for the central metallic unit alone.

Characterization of Molybdenum Dithiocarbamates by First-Principles Calculations.

Molybdenum dithiocarbamate (MoDTC) is a well-known lubricant additive, which, in tribological conditions, is capable of forming layers of MoS with excellent friction reduction properties. Despite being widely employed in commercial engine oils, a comprehensive theoretical description of the properties of MoDTC is still lacking. In this work, we employ density functional theory to study the structural, electronic, and vibrational properties of MoDTC.