Positron Lifetimes in Solids from First Principles Calculations

D ec 1 99 9 FIRST - PRINCIPLES CALCULATIONS OF POSITRON ANNIHILATION IN SOLIDS

We present first-principles approaches based on density functional theory for calculating positron states and annihilation characteristics in condensed matter. The treatment of the electron-positron correlation effects (the enhancement of the electron density at the positron with respect to mean-field density) is shown to play a crucial role when calculating the annihilation rates. A generalize...

Ammonia synthesis from first-principles calculations.

The rate of ammonia synthesis over a nanoparticle ruthenium catalyst can be calculated directly on the basis of a quantum chemical treatment of the problem using density functional theory. We compared the results to measured rates over a ruthenium catalyst supported on magnesium aluminum spinel. When the size distribution of ruthenium particles measured by transmission electron microscopy was u...

Tight-binding Hamiltonian from first-principles calculations

The tight-binding method attempts to represent the electronic structure of condensed matter using a minimal atomic-orbital like basis set. To compute tight-binding overlap and Hamiltonian matrices directly from first-principles calculations is a subject of continuous interest. Usually, first-principles calculations are done using a large basis set or long-ranged basis set (e.g. muffin-tin orbit...

Magnetism of Chromia from First-Principles Calculations

First Principles Calculations

Calculations of the linestrengths and transition frequencies of the forbidden pure rotational spectrum of Hz in the vibrationally excited v2 state are presented. These transitions occur in the far-infrared region, and their observation may be complicated by vi u2 difference transitions. Examples of these are also given. Forbidden rovibrational transition frequencies and linestrengths have also ...