2D Slab Models of Nanotubes Based on Tetragonal TiO2 Structures: Validation over a Diameter Range

One-dimensional nanomaterials receive much attention thanks to their advantageous properties compared to simple, bulk materials. A particular application of 1D nanomaterials is photocatalytic hydrogen generation from water. Such materials are studied not only experimentally, but also computationally. The bottleneck in computations is insufficient computational power to access realistic systems, especially with water or another adsorbed species, using computationally expensive methods, such as ab initio MD. Still, such calculations are necessary for an in-depth understanding of many processes, while the available approximations and simplifications are either not precise or system-dependent. Two-dimensional models as an approximation for TiO2 nanotubes with (101) and (001) structures were proposed by our group for the first time in Comput. Condens. Matter journal in 2018. They were developed at the inexpensive DFT theory level. The principle was to adopt lattice constants from an NT with a specific diameter and keep them fixed in the 2D model optimization, with geometry modifications for one of the models. Our previous work was limited to studying one configuration of a nanotube per 2D model. In this article one of the models was chosen and tested for four different configurations of TiO2 nanotubes: (101) (n,0), (101) (0,n), (001) (n,0), and (001) (0,n). All of them are 6-layered and have rectangular unit cells of tetragonal anatase form. Results of the current study show that the proposed 2D model is indeed universally applicable for different nanotube configurations so that it can be useful in facilitating computationally costly calculations of large systems with adsorbates.

Interfacial fluorine migration-induced low leakage conduction in PVA based high-k composites with V2C MXene-SWCNT switchboard-like ceramic via ab initio MD simulations

Using V2C-CNT switchboard-like hybrid particles as filler for preparing promising composite dielectrics based on fluorine-migration effect.

Hydrogen Intramolecular Stretch Redshift in the Electrostatic Environment of Type II Clathrate Hydrates from Schrödinger Equation Treatment

The one-dimensional Schrödinger equation, applied to the H2 intramolecular stretch coordinate in singly to quadruply occupied large cages in extended Type II (sII) hydrogen clathrate hydrate, was solved numerically herein via potential-energy scans from classical molecular dynamics (MD), employing bespoke force-matched H2–water potential. For both occupation cases, the resultant H–H stretch spectra were redshifted by ~350 cm−1 vis-à-vis their classically sampled counterparts, yielding semi-quantitative agreement with experimental Raman spectra. In addition, ab initio MD was carried out systematically for different cage occupations in the extended sII hydrate to assess the effect of differing intra-cage intrinsic electric field milieux on H–H stretch frequencies; we suggest that spatial heterogeneity of the electrostatic environment is responsible for some degree of peak splitting.

The multiple dissociation constants of glutathione disulfide: interpreting experimental pH-titration curves with ab initio MD simulations

Dissociation constants calculated from ab initio MD simulations can aid the interpretation of the pH-titration curves of complex systems.

Formation Conditions for Epitaxial Graphene on Diamond (111) Surfaces

The phase transformation from a non-terminated diamond (111) surface to graphene has in the present study been simulated by using ab initio MD calculations at different temperatures and under various reaction conditions. For strict vacuum conditions, the graphitization process was observed to start at about 800 K, with a final graphene-like ad layer obtained at 2500 K. The C-C bonds across the interface were found to be broken gradually with an increase in temperature. The resulting graphene-like ad layer at 2500 K was observed to chemisorb to the underlying diamond surface with 33% of the initial C-C bonds, and with a C-C covalent energy value of 3.4 eV. The corresponding DOS spectra showed a p-doped character, as compared with graphene. When introducing H radicals during the annealing process, a graphene-like ad layer started to be formed at a much lower temperature; 500K.The completeness of the diamond-to-graphene process was found to strongly depend on the concentration of H radicals. When introducing a larger concentration of H radicals into the lattice in the initial part of the annealing process, the formation of a free-standing graphene layer was observed to take place at an even lower H concentration and temperature (1000 K).

How silver segregation stabilizes 1D surface gold oxide: a cluster expansion study combined with ab initio MD simulations

Gold surprises us again by the unusual stability of one-dimensional gold oxide structures supported on bimetallic surfaces of gold and silver.