DFT calculations for structural prediction and applications of intercalated lamellar compounds.

The intercalated layered materials are commonly built from structures complex enough to have large unit cells and, because of this, calculations of their electronic structures are very demanding in terms of memory, processing and time. Also, the versatility of these compounds enables the synthesis of a large number of derived materials difficult to characterize. Only in the last two decades, a combination of theoretical methodologies and advances in processing made density-functional theory (DFT) calculations quite interesting as an investigation tool for this family of materials. Since the intercalated layered or lamellar compounds correspond to a large group of important classes of materials and their experimental data were, and are still being, generated, only a small part of the data comes from electronic structure simulations. In this review, we have listed some relevant types of intercalated lamellar materials, the useful methodologies implemented in the standard suit of codes for DFT calculations and examples of the many applications of the calculations to the understanding of physical and chemical properties, to the planning of novel materials with desirable properties, and even to assist the structural characterization, by simulating complex results from nuclear magnetic resonance, vibrational spectroscopy and powder X-ray diffraction. In addition to the properties simulated directly as observables, other quantities such as density of states, partial charges and electronic density difference, provide relevant information about the materials and their behavior under diverse physical and chemical conditions. The combination of the geometric, electronic and vibrational structures also leads to the simulations of thermodynamic potentials, entropy and phase diagrams in the solid state. This significant ensemble of research tools makes DFT calculations very compelling and useful to gain new insights into innovation developments for intercalated lamellar materials.

Ligand-assisted preparation of palladium supported nanoparticles: a step toward size control.

Supported nanoparticles (SNPs) with narrow size distribution were prepared by H(2) reduction of Pd(2+) previously bound to ligand-modified silica surfaces. Interestingly, the size of the Pd(0) SNPs was tuned by the ligand grafted on the support surface. Amino- and ethylenediamino-functionalized supports formed Pd(0) SNPs of ca. 6 and 1 nm, respectively. The catalytic properties of both Pd(0) SNPs were investigated.