Leif Gerward

Bio: Leif Gerward is an academic researcher from Technical University of Denmark. The author has contributed to research in topics: Bulk modulus & Effective atomic number. The author has an hindex of 25, co-authored 67 publications receiving 3210 citations.

On the effective atomic number and electron density: A comprehensive set of formulas for all types of materials and energies above 1 keV

Abstract: A comprehensive and consistent set of formulas is given for calculating the effective atomic number and electron density for all types of materials and for all photon energies greater than 1 keV The formulas are derived from first principles using photon interaction cross sections of the constituent atoms The theory is illustrated by calculations and experiments for molecules of medical and biological interest, glasses for radiation shielding, alloys, minerals and liquids

High-pressure polymorphs of anatase TiO 2

Abstract: The equation of state of anatase ${\mathrm{TiO}}_{2}$ has been determined experimentally---using polycrystalline as well as single-crystal material---and compared with theoretical calculations using the ab initio perturbed ion model. The results are highly consistent, the zero-pressure bulk modulus being 179(2) GPa from experiment and 189 GPa from theory. Single-crystal tetragonal anatase transforms to the orthorhombic $\ensuremath{\alpha}\ensuremath{-}{\mathrm{PbO}}_{2}$ structure at about 4.5 GPa. This transition is suppressed in the polycrystalline material at room temperature, probably due to the presence of grain boundaries and other crystal defects. Polycrystalline anatase is found to transform to the monoclinic baddeleyite structure at about 13 GPa. Upon decompression, the baddeleyite phase transforms to the $\ensuremath{\alpha}\ensuremath{-}{\mathrm{PbO}}_{2}$ phase at about 7 GPa. The experimental zero-pressure bulk moduli are 258(8) GPa for the $\ensuremath{\alpha}\ensuremath{-}{\mathrm{PbO}}_{2}$ phase and 290(10) GPa for the baddeleyite phase.

Review of the anatase to rutile phase transformation

Abstract: Titanium dioxide, TiO2, is an important photocatalytic material that exists as two main polymorphs, anatase and rutile. The presence of either or both of these phases impacts on the photocatalytic performance of the material. The present work reviews the anatase to rutile phase transformation. The synthesis and properties of anatase and rutile are examined, followed by a discussion of the thermodynamics of the phase transformation and the factors affecting its observation. A comprehensive analysis of the reported effects of dopants on the anatase to rutile phase transformation and the mechanisms by which these effects are brought about is presented in this review, yielding a plot of the cationic radius versus the valence characterised by a distinct boundary between inhibitors and promoters of the phase transformation. Further, the likely effects of dopant elements, including those for which experimental data are unavailable, on the phase transformation are deduced and presented on the basis of this analysis.

Introduction to Spectroscopy

Abstract: Spectroscopy is the study of matter interacting with electromagnetic radiation (e.g., light). The electromagnetic spectrum in Figure 1 illustrates the many different types of electromagnetic radiation, including gamma rays (γ-rays), X-rays, ultraviolet (UV) radiation, visible light, infrared (IR) radiation, microwaves, and radio waves. The frequency (ν) and wavelength (λ) ranges associated with each form of radiant energy are also indicated in Figure 1.