Thermoelectric nanomaterials, whose combination of thermal, electrical, and semiconducting properties allows them to convert heat into electricity, are expected to play an increasingly important role in meeting the energy challenge of the future. Major advances in this field strongly depend on our fundamental understanding of heat and charge carrier transport and on the ability of finding new strategies to design and fabricate high efficiency thermoelectric devices and circuits. Despite of the substantial advances in the description of thermal and electronic dynamics in bulk materials, the extension of transport bulk theory to nanostructures, is still under development. One of the main problems in modeling the nanostructures for thermoelectrics is the fact that they usually have complex compositions and structures. To these complex structures, usually, several external elements are added to improve either the thermoelectric properties and to become functional elements of devices and circuits. The final material is hence a quite complex object whose phononic and electronic structure is unknown. Continue reading Advanced thermoelectrics at nanoscale: from materials to devices→
Due to recent progress in nano-fabrication there is a large, growing interest in stabilized metal-organic hybrids. However, at present not many computational ab-initio studies have been performed and they are scattered across different fields and communities. The workshop goal was then to address current challenges and successful methods to study the electronic properties of organo-metal nanocomposites bringing together leading scientists working both on ground and excited state electronic properties of organic stabilized metal complexes.
In recent years we have been observing huge progress in first principles defect science. However, due to the widespread interest in defects, new developments have been disconnected with little crosstalk between the various disciplines and communities. In our experience, defects are typically discussed at topical conferences on specific materials or material classes. It was our aim to change this state of affairs with our proposed workshop.
By pooling expertise in a single event we intended to provide a unique opportunity for assessing the current state of the field. We have brought together a representative selection of distinguished researchers in defect science. In oral presentations, the invited speakers have addressed the different aspects of the grand challenges at stake in the modelisation of defects. Ample discussion time has been reserved after each presentation to reflect on the immediate challenge and its ramifications. In addition, we have organized a round table discussion, in which general interest topics that do not fit the regular scientific talks have been discussed.
Theory of Heusler and Full-Heusler Compounds
Iosif Galanakis Department of Materials Science, School of Natural Sciences, University of Patras, GR-26504 Patra, Greece
Spintronics/magnetoelectronics brought at the centre of scientific research the Heusler and full-Heusler compounds, since several among them have been shown to be half-metals. In this review we present a study of the basic electronic and magnetic properties of both Heusler families; the so-called semi-Heusler alloys like NiMnSb and the full-Heusler alloys like Co2MnGe (usual full-Heuslers), Mn2CoAl (inverse full-Heuslers) and (CoFe)MnAl (LiMgPdSn-type full-Heuslers). First-principles calculations are employed to discuss the origin of the gap which is fundamental for the understanding of their electronic and magnetic properties. For half-metallic Heusler compounds the total spin magnetic moment Mt scales linearly with the number of the valence electrons Zt in the unit cell. These simple rules connect directly the magnetic to the electronic properties opening the way to engineer new half-metallic alloys with ”à la carte” magnetic properties such as the quaternary half-metals, the so-called half-metallic antiferromagnets, magnetic semiconductors or even the more exotic spin-gapless semiconductors. Finally, special topics like exchange constants, defects, vacancies, surfaces and interfaces are being discussed.
This new Psi-k web site is dedicated to Walter Temmerman (1950-2014) who, with his wife Zdzislawa Szotek, was one of the key figures involved in the conception, foundation, and success of Psi-k in Europe.
Ab initio (from electronic structure) calculation of complex processes in materials