A new density functional (DF) of the generalized gradient approximation (GGA) type for general chemistry applications termed B97-D is proposed. It is based on Becke's power-series ansatz from 1997 and is explicitly parameterized by including damped atom-pairwise dispersion corrections of the form C(6) x R(-6). A general computational scheme for the parameters used in this correction has been established and parameters for elements up to xenon and a scaling factor for the dispersion part for several common density functionals (BLYP, PBE, TPSS, B3LYP) are reported. The new functional is tested in comparison with other GGAs and the B3LYP hybrid functional on standard thermochemical benchmark sets, for 40 noncovalently bound complexes, including large stacked aromatic molecules and group II element clusters, and for the computation of molecular geometries. Further cross-validation tests were performed for organometallic reactions and other difficult problems for standard functionals. In summary, it is found that B97-D belongs to one of the most accurate general purpose GGAs, reaching, for example for the G97/2 set of heat of formations, a mean absolute deviation of only 3.8 kcal mol(-1). The performance for noncovalently bound systems including many pure van der Waals complexes is exceptionally good, reaching on the average CCSD(T) accuracy. The basic strategy in the development to restrict the density functional description to shorter electron correlation lengths scales and to describe situations with medium to large interatomic distances by damped C(6) x R(-6) terms seems to be very successful, as demonstrated for some notoriously difficult reactions. As an example, for the isomerization of larger branched to linear alkanes, B97-D is the only DF available that yields the right sign for the energy difference. From a practical point of view, the new functional seems to be quite robust and it is thus suggested as an efficient and accurate quantum chemical method for large systems where dispersion forces are of general importance.

Semiempirical GGA-type density functional constructed with a long-range dispersion correction.

The reduction of graphene oxide

Mechanical properties of nanocrystalline materials

Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

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Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

Dangling bond surfaces states in (111) faces of zinc-blende compounds

The behavior of the metal-semiconductor junction is studied for some III-V and II-VI zinc-blende compounds, within the framework of a one-electron theory. Using a pseudopotential description of the semiconductor crystals, the density of interface states is analyzed performing the matching of the wave functions at the interface. The characteristics of the different types of interface states are discussed in detail, and particular examples are given for contacts with metals of high and low electronic densities. As a by-product, the surface states at the semiconductor vacuum interface are also calculated. Finally, the barrier potential of the junction is obtained as a function of the metal work function (for metals of high density). Although very good agreement has been found with the experimental data for the compounds of the covalent group, large discrepancies arise for those of the ionic group. Some comments on the reasons for these discrepancies are made.

Metal-semiconductor Junctions for (110) Surfaces of Zinc-blende Compounds

It is argued that, since the average phase of the wavefunction is uniquely fixed by charge neutrality, for the purpose of calculating dangling-bond surface states in narrow-gap semiconductors, a self-consistent barrier can be replaced by a suitably displaced abrupt barrier. This yields a simple scheme which can be used to calculate the eigenvalue E(k) for any desired k. Calculations are carried our for Si and Ge, and compared with self-consistent calculations where available.

https://iopscience.iop.org/article/10.1088/0022-3719/9/16/004/pdf

Displaced abrupt barrier and self-consistency of dangling-bond surface states

2014 A 1-dimensional covalent surface is first studied selfconsistently within the narrow gap approximation. Our analysis shows : i) that the potential and charge distribution in the surface region behave rather like those for the case of a metal, and ii) that the dangling-bond surface state is determined by a charge neutrality sum-rule. A covalent 111-surface is then discussed. Our arguments strongly suggest that the same conclusions apply to this surface. By using these results, the 111-Si surface potential has been obtained and compared satisfactorily with other independent theoretical calculations. LE JOURNAL DE PHYSIQUE TOME 38, AOUT 1977,

Fernando Flores

Papers

Dangling bond surfaces states in (111) faces of zinc-blende compounds

Metal-semiconductor Junctions for (110) Surfaces of Zinc-blende Compounds

Displaced abrupt barrier and self-consistency of dangling-bond surface states

A simple approach to covalent surfaces

Initial stages of the Schottky-barrier formation for abrupt covalent interfaces