Anomalous Thermal Stability of Metastable C_20 Fullerene

The results of computer simulation of the dynamics of fullerene C_20 at different temperatures are presented. It is shown that, although it is metastable, this isomer is very stable with respect to the transition to a lower energy configuration and retains its chemical structure under heating to very high temperatures, T ~ 3000 K. Its decay activation energy is found to be E_a ~ 7 eV. Possible decay channels are studied, and the height of the minimum potential barrier to decay is determined to be U = 5.0 eV. The results obtained make it possible to understand the reasons for the anomalous stability of fullerene C_20 under normal conditions.Comment: Slightly corrected version of the paper submitted to Phys. Solid Stat

Memory effect in the deposition of C20 fullerenes on a diamond surface

In this paper, the deposition of C-20 fullerenes on a diamond (001)-(2x1) surface and the fabrication of C-20 thin film at 100 K were investigated by a molecular dynamics (MD) simulation using the many-body Brenner bond order potential. First, we found that the collision dynamic of a single C-20 fullerene on a diamond surface was strongly dependent on its impact energy. Within the energy range 10-45 eV, the C-20 fullerene chemisorbed on the surface retained its free cage structure. This is consistent with the experimental observation, where it was called the memory effect in "C-20-type" films [P. Melion , Int. J. Mod. B 9, 339 (1995); P. Milani , Cluster Beam Synthesis of Nanostructured Materials (Springer, Berlin, 1999)]. Next, more than one hundred C-20 (10-25 eV) were deposited one after the other onto the surface. The initial growth stage of C-20 thin film was observed to be in the three-dimensional island mode. The randomly deposited C-20 fullerenes stacked on diamond surface and acted as building blocks forming a polymerlike structure. The assembled film was also highly porous due to cluster-cluster interaction. The bond angle distribution and the neighbor-atom-number distribution of the film presented a well-defined local order, which is of sp(3) hybridization character, the same as that of a free C-20 cage. These simulation results are again in good agreement with the experimental observation. Finally, the deposited C-20 film showed high stability even when the temperature was raised up to 1500 K

Optimizing link atom parameters for DNA QM/MM simulations

This work optimizes the link bond description of the quantum mechanical/molecular mechanical separation of deoxynucleosides. The nucleosides are separated at the CN bond between the nucleobase and the deoxyribose, with the former acting as the quantum mechanically described species. By using a flexible link atom-ansatz plus a harmonic potential to correct the energy deviation from a full quantum mechanical description, the potential energy well of the bonds stretching motion is mimicked with very high accuracy.(VLID)454131

Tetrachloroaluminate Ion on Graphene Quantum Dots: Towards the Design of Cathode for Aluminum-ion Battery

Abstract The adsorption of tetrachloroaluminate, AlCl4 −, on Graphene Quantum Dot (GQD) were studied using Density Functional Theory (DFT). Coronene (C24H12) and circumcoronene (C54H18) were used as the model of GQDs. All possible adsorption sites which include hollow, bridge, and on-top as well as three possible standing positions of AlCl4 − were investigated. AlCl4 − can be adsorbed on the GQD surface with the adsorption energy of -2.35 to -2.83 eV for the charging condition. The adsorption energy of AlCl4 − during charging is around 10 times that during discharging. From our study, GQDs can be used as cathode material for Aluminum-ion Battery (AIB) providing higher voltage than graphite. The theoretical voltage for coronene and circumcoronene was found to be 4.3V and 4.0 V, respectively.</jats:p

Recent Developments in Integral Equation Theory for Solvation to Treat Density Inhomogeneity at Solute–Solvent Interface

The integration equation theory (IET) provides highly efficient tools for the calculation of structural and thermodynamic properties of molecular liquids. In recent years, the 3D reference interaction site model (3DRISM), the most developed IET for solvation, has been widely applied to study protein solvation, aggregation, and drug‐receptor binding. However, hydrophobic solutes with sufficient size (>nm) can induce water density depletion at the solute–solvent interface. This density depletion is not considered in the original 3DRISM theory. The authors here review the recent developments of 3DRISM at hydrophobic surfaces and related theories to address this challenge. At hydrophobic surfaces, an additional hydrophobicity‐induced density inhomogeneity equation is introduced to 3DRISM theory to consider this density depletion. Accordingly, several new closures equations including D2 closure and D2MSA closures are developed to enable stable numerical solutions of 3DRISM equations. These newly developed theories hold great promise for an accurate and rapid calculation of the solvation effect for complex molecular systems such as proteins. At the end of the report, the authors also provide a perspective on other challenges of the IETs as an efficient solvation model