We reveal for the first time through a theoretical first-principles study that the adsorption of a nonmagnetic π-conjugated organic molecule on a ferromagnetic surface locally increases the strength of the magnetic exchange interaction between the magnetic atoms binding directly to the molecule. This magnetic hardening effect leads to the creation of a local molecular mediated magnetic unit with a stable magnetization direction and an enhanced barrier for the magnetization switching as compared to the clean surface. Remarkably, such a hybrid organic-ferromagnetic system exhibits also a spin-filter functionality with sharp spin-split molecularlike electronic features at the molecular site.

Most of the large variety of 2D materials are derived from their parent van der Waals (vdWs) crystals, thus their atomic struc tures are identical to the bulk counterparts with some minor lattice constant differ ence due to the reduced dimensionality and vanished interlayer interaction. Simi larly, some 2D monolayers, of which a typical example would be silicene, [10] stem from bulk materials with covalent bonds. Although their bonding may significantly change (silicene: sp 2 ; bulk silicon: sp 3 ) when they go from the bulk material to the 2D monolayer, their atomic structures are analogous. However, a slight atomic relaxation may occur in order to balance the reduced bonding coordination in the 2D forms. Therefore, in these cases, the determination of the 2D atomic structures is quite straightforward.In contrast, most metal oxides feature strong interlayer ionic bonds. The lack of a strong interlayer interaction in their 2D forms usually introduces dangling bonds, leading to strong surface polarization which induces surface instability of 2D metal oxides. Pronounced lattice relaxation, prominent struc tural reconstruction and substrate effects have been identified as the main mechanisms for compensating such strong sur face polarization in 2D metal oxides, as have been observed for a Pd 5 O 4 overlayer on Pd(111), [22] a strained PdO(101) layer on Pd (100), [23] a Ag 1.83 O trilayer on Ag(111), [24] a RhO 2 trilayer on Rh(111), [25] multiple phases of 2D Mn oxides on Pd(100), [26] and TiO 2 on rutile TiO 2 (011). [27] All of these significant changes increase the difficulty of synthesizing 2D metal oxides, as well as pose a challenge to computational structure prediction methods. Notwithstanding, more recently, spectacular progress has been made in prediction, design, preparation, and charac terization of oxide monolayers owing to the advancement of growth technologies and novel synthesis routes, as well as the development of computational and theoretical methods. [28][29][30][31][32][33] The structural reconstructions in combination with the elec tron confinement in 2D and the large surfacetovolume ratio endow 2D transition metal oxides (TMOs) with stunning physical/chemical properties. Moreover, the 2D TMOs showThe discovery of graphene has stimulated dramatic research interest on other 2D materials including transition metal oxide (TMO) monolayers in order to realize novel functionalization and applications. Due to reduced bonding coordination and strong surface polarization, the structures of most TMOs in the monolayer limit are very different from their bulk counterparts, as well as their physical and chemical properties. In this brief review, the authors sum marize recent research progress on atomically thin TMO layers. The focus is on the structural properties of the TMOs and their interaction with the sub strates from the computational point of view. The authors also introduce the potential applications of the TMO 2D materials on supercapacitors, photo catalysts, batteries, and sensors.

The adsorption mechanism of single thiophene (C 4 H 4 S), 4-thiophene (C 16 H 10 S 4 ), and their dimers on the Cu(111) surface has been studied in the framework of the density functional theory (DFT). The importance of the London dispersion effects on the molecule-surface adsorption geometry and the corresponding binding energy was investigated by using semiempirical and first-principles methods. Interestingly, the physisorption character of the thiophene bonding on Cu(111) suggested by strength of the molecule-surface interaction as revealed by the DFT calculations turns out to be a weak chemisorption even for the DFT ground-state geometry when a nonlocal correlation energy functional [Dion et al., Phys. Rev. Lett. 92, 246401 (2004)] is used. Our ab initio calculations also suggest that the formation of thiophene and 4-thiophene dimers is energetically favorable with respect to the adsorption of single molecules.

The solvation and desolvation of the Li ion play a crucial role in the electrolytes of Li based secondary batteries, and their understanding at the microscopic level is of great importance. Oligoether (glyme) based electrolytes have attracted much attention as electrolytes used in Li based secondary batteries, such as Li-ion, Li-S, and Li-O batteries. However, the solvation structure of the Li ion in glyme based electrolytes has not been fully clarified yet. We present a computational study on the solvation structure of lithium ions in the mixture of triglyme and lithium bis(trifluoromethylsulfonyl)-amide (LiTFSA) by means of molecular orbital and molecular dynamics calculations based on density functional theory. We found that, in the electrolyte solution composed of the equimolar mixture of triglyme and LiTFSA, lithium ions are solvated mainly by crown-ether-like curled triglyme molecules and in direct contact with an TFSA anion. We also found the aggregate formed with Li ion and TFSA anions and/or triglyme molecule(s) is equally stable, which has not been reported in the previous classical molecular dynamics simulations, suggesting that in reality a small fraction of Li ions form aggregates and they might have a significant impact on the Li ion transport. Our results demonstrate the importance of performing electronic structure based molecular dynamics of electrolyte solution to clarify the detailed solvation structure of the Li ion.

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We have performed a systematic semi-empirical and ab initio van der Waals study to investigate the bonding mechanism of benzene (C(6)H(6)), triazine (C(3)N(3)H(3)) and borazine (B(3)N(3)H(6)) adsorbed on graphene and a single boron nitride (BN) sheet. The two semi-empirical approaches used to include the van der Waals (vdW) interactions in our density functional theory (DFT) calculations suggest that the strength of the molecule-surface interaction corresponds to a strong physisorption with no net charge transfer between the molecules and the corresponding substrates. This observation is strengthened by the use of first-principles non-local correlation vdW-DF functionals which provide a sound physical basis to include vdW interactions in DFT calculations. In particular we have employed two flavors of vdW-DF functionals which enabled us to determine the role of the non-local correlation effects in the molecule-surface bonding mechanism which cannot be assessed by using only semi-empirical vdW methods. Our study also reveals that the strength of the molecule-surface interaction can be influenced by the electronegativity of the B, C and N atoms.

The miniaturization of future electronic devices requires the knowledge of interfacial properties between two-dimensional channel materials and high-κ dielectrics in the limit of one atomic layer thickness. In this report, by combining particle-swarm optimization method with first-principles calculations, we present a detailed study of structural, electronic, mechanical, and dielectric properties of Al2O3 monolayer. We predict that planar Al2O3 monolayer is globally stable with a direct band gap of 5.99 eV and thermal stability up to 1100 K. The stability of this high-κ oxide monolayer can be enhanced by substrates such as graphene, for which the interfacial interaction is found to be weak. The band offsets between the Al2O3 monolayer and graphene are large enough for electronic applications. Our results not only predict a stable high-κ oxide monolayer, but also improve the understanding of interfacial properties between a high-κ dielectric monolayer and two-dimensional material.

We demonstrate that cyclooctatetraene (COT) can be stabilised in different conformations when adsorbed on different noble-metal surfaces due to varying molecule-substrate interactions. While at first glance the behaviour seems to be in accordance with Hückel's rule, a theoretical analysis reveals no significant charge transfer. The driving mechanism for the conformational change is hybridisation at the organic-metal interface and does not necessitate any charge transfer.