Ab initio study of the p-hole magnetism at polar surfaces of ZnO: the role of correlations.

A standard local density approximation and its self-interaction corrected version are applied to study spontaneous magnetization, promoted by localized p electron holes, of polar oxygen-terminated ZnO surfaces. The electronic properties and magnetic exchange interactions of three different facets are calculated. It is demonstrated that partially filled oxygen p orbitals of the polar surfaces exhibit magnetic moment formation and long range magnetic order leading to the occurrence of a ferromagnetic ground state. Monte Carlo simulations predict Curie temperatures above room temperature. In contrast to isolated defects in bulk materials, applying correlation corrections to the localized p-like surface states does not lead to a collapse of magnetic interaction: as the weakening of the magnetic interaction, caused by the reduced electronic overlap, is compensated by a strengthening due to an increase of the magnetic moments, the ferromagnetism can principally persist above room temperature, provided a large hole concentration exists.

Magnetic properties of bcc Iron surfaces and the influence of the chemical environment: electronic structure calculations.

We have investigated the magnetic properties of low-indexed iron surfaces and the influence of the chemical environment on these properties. We have considered the (1 0 0), (1 1 0), (1 1 1), (2 1 1) and (3 1 0) surfaces, both, bare and with the presence of adsorbates. These were chosen to mimic realistic chemical synthesis environments, being H, Cl, HCl, NH3, NH4Cl, or CH3COOH. We have found an increased magnetization at all bare surfaces. Upon H adsorption the magnetization is generally reduced, but still above the bulk value. All other ligands and their dissociated parts alter the magnetic properties of the surfaces only weakly. Our calculations do not indicate that ligands are responsible for experimental observations of Fe nanoparticles with average magnetizations below the bulk value.

Surfaces of a colloidal iron nanoparticle in its chemical environment: a DFT description.

Describing and understanding surface chemistry on the atomic scale is of primary importance in predicting and rationalize nanoparticle morphology as well as their physical and chemical properties. Here we present the results of comprehensive density functional theory studies on the adsorption of several small organic species, representing the major species (H2, Cl2, HCl, NH3, NH4Cl, and CH3COOH), present in the reaction medium during colloidal iron nanoparticle synthesis on various low-index iron surface models, namely, (100), (110), (111), (211), and (310). All of the tested ligands strongly interact with the proposed surfaces. Surface energies are calculated and ligand effects on the morphologies are presented, including temperature effects, based on a thermodynamic approach combined with the Wulff construction scheme. The importance of taking into account vibrational contributions during the calculation of surface energies after adsorption is clearly demonstrated. More importantly, we find that thermodynamic ligand effects can be ruled out as the unique driving force in the formation of recently experimentally observed iron cubic nanoparticles.

[Outpatient anesthesia--the office-based anesthetist]. / Ambulante Anästhesie--Der niedergelassene Anästhesist.

The aim of the present article is to describe the field of activity and prevailing conditions for office-based anesthetists in Germany. From the introduction of outpatient operations on the basis of actual numbers, data and facts, we present the project profile and the structures of the different fields of activity and practice constellations for office-based anesthesiology. Particular emphasis is placed on the requirements for room space and technical facilities, the criteria for patient selection, and the structural and procedural quality as well as quality management of outpatient anesthesia. With the aid of current numerical data the anesthetic procedures performed in the outpatient field through to the possibilities for development of continuous regional anesthetic procedures in catheter technique are illustrated. In conclusion, we discuss the economic conditions and the health-care economic significance together with a description of the current health-care quality of ambulant anesthesiology and the possibilities for participation in an error-reporting system.