Phase diagram of solid-phase transformation in amorphous carbon nanorods.

The transformations of amorphous carbon nanorods with different diameters and densities upon heating up to different temperatures are studied with density-functional-based tight-binding molecular dynamics. Phase diagrams with assorted transformed sp(2) nanostructures depending on both temperatures and line density, under different heating treatments, are presented to place the observations in perspective. Under instant heating, the lowest line density at which a carbon nanotube can form is 8 Å(-1), while a double-walled carbon nanotube can form at a linear density of 19-20 Å(-1) and higher.

The mechanism of transforming diamond nanowires to carbon nanostructures.

The transformation of diamond nanowires (DNWs) with different diameters and geometries upon heating is investigated with density-functional-based tight-binding molecular dynamics. DNWs of {100} and {111} oriented cross-section with projected average line density between 7 and 20 atoms Å(-1) transform into carbon nanotubes (CNTs) under gradual heating up to 3500-4000 K. DNWs with projected average line density larger than 25 atoms Å(-1) transform into double-wall CNTs.

A hydrothermal anvil made of graphene nanobubbles on diamond.

The hardness and virtual incompressibility of diamond allow it to be used in high-pressure anvil cell. Here we report a new way to generate static pressure by encapsulating single-crystal diamond with graphene membrane, the latter is well known for its superior nano-indentation strength and in-plane rigidity. Heating the diamond-graphene interface to the reconstruction temperature of diamond (~1,275 K) produces a high density of graphene nanobubbles that can trap water.

Three-stage transformation pathway from nanodiamonds to fullerenes.

The dynamics of structure evolution of nanodiamonds ranging from 22 to 318 atoms of various shapes is studied by density functional tight-binding molecular dynamics. The spherical and cubic nanodiamonds can be transformed into fullerene-like structures upon heating. A number of the transformed fullerenes consist of pentagons and hexagons only.

Energies, Geometries, and Charge Distributions of Zn Molecules, Clusters, and Biocenters from Coupled Cluster, Density Functional, and Neglect of Diatomic Differential Overlap Models.

We present benchmark databases of Zn-ligand bond distances, bond angles, dipole moments, and bond dissociation energies for Zn-containing small molecules and Zn coordination compounds with H, CH3, C2H5, NH3, O, OH, H2O, F, Cl, S, and SCH3 ligands. The test set also includes clusters with Zn-Zn bonds. In addition, we calculated dipole moments and binding energies for Zn centers in coordination environments taken from zinc metalloenzyme X-ray structures, representing both structural and catalytic zinc centers.

Application of the Electrostatically Embedded Many-Body Expansion to Microsolvation of Ammonia in Water Clusters.

The electrostatically embedded many-body expansion (EE-MB), at both the second and third order, that is, the electrostatically embedded pairwise additive (EE-PA) approximation and the electrostatically embedded three-body (EE-3B) approximation, are tested for mixed ammonia-water clusters. We examine tetramers, pentamers, and hexamers for three different density functionals and two levels of wave function theory, We compare the many-body results to the results of full calculations performed without many-body expansions. Because of the differing charge distributions in the two kinds of monomers, this provides a different kind of test of the usefulness of the EE-MB method than was provided by previous tests on pure water clusters.

Density Functional Theory in Transition-Metal Chemistry: Relative Energies of Low-Lying States of Iron Compounds and the Effect of Spatial Symmetry Breaking.

The ground and lower excited states of Fe2, Fe2(-), and FeO(+) were studied using a number of density functional theory (DFT) methods. Specific attention was paid to the relative state energies, the internuclear distances (re), and the harmonic vibrational frequencies (ωe). A number of factors influencing the calculated values of these properties were examined.