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1. 1. Disordered Icosahedral Boron-Rich Solids : A Theoretical Study of Thermodynamic Stability and Properties

   Författare :Annop Ektarawong; Björn Alling; Michael Widom; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Icosahedral boron-rich solids; Boron carbide; Configurational disorder; First-principles calculations; Thermodynamic stability; Superatom-special quasirandom structure;

   Sammanfattning : This thesis is a theoretical study of configurational disorder in icosahedral boron-rich solids, in particular boron carbide, including also the development of a methodological framework for treating configurational disorder in such materials, namely superatom-special quasirandom structure (SA-SQS). In terms of its practical implementations, the SA-SQS method is demonstrated to be capable of efficiently modeling configurational disorder in icosahedral boron-rich solids, whiles the thermodynamic stability as well as the properties of the configurationally disordered icosahedral boron-rich solids, modeled from the SA-SQS method, can be directly investigated, using the density functional theory (DFT). LÄS MER

3. 2. Phase Transformations in Computer Simulated Icosahedrally Ordered Phases

   Författare :Fredrik Zetterling; KTH; []
   Nyckelord :simpl liquids; molecular dynamics; pair potential; icosahedral custer;

   Sammanfattning : Computer simulations play a profound and fundamental role inmodern theoretical physics, chemistry and materials science. Tounderstand the complex physics of metally liquids, metals,quasicrystals and metally glasses a working model imposing thelocal and global order is needed. LÄS MER

4. 3. Frustrated magnetism in icosahedral structures : The influence of order-disorder in quasicrystals and approximant crystals

   Författare :Fernand Denoel; Roland Mathieu; Marc de Boissieu; Uppsala universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; quasicrystals; approximant crystals; spin glasses; SQUID magnetometry; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

   Sammanfattning : This work will begin with an introduction to quasicrystals (QCs) and their structure, defining the unit cell-equivalent for icosahedral quasiperiodicity: a 3D tiling based on the golden ratio and aperiodic in all three dimensions. We briefly present the cut-and-project method used to generate QCs from a higher dimension hypercrystal, and how to build the 3D Penrose tilings, composed of the two golden rhombohedra. LÄS MER

5. 4. Computer simulations of condensed phases with icosahedral local order

   Författare :Sergei Simdyankin; Paul Madden; Stockholms universitet; []
   Nyckelord :SAMHÄLLSVETENSKAP; SOCIAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; simple liquids; glasses; liquid-glass transition; Frank-Kasper phase; molecular dynamics; phonon dispersion; normal-mode analysis; wavelet analysis; numerisk analys; Numerical Analysis;

   Sammanfattning : Understanding the fundamental aspects, and the formation mechanisms of glasses remains an outstanding unsolved problem of condensed-matter physics.Glass-formation in simple atomic systems is generally associated with the icosahedral local order. LÄS MER

7. 5. Simulation of the Melting and Cooling of Palladium Clusters

   Författare :Jan Westergren; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; melting; energy transfer; density of states; metal clusters; cooling; collision; phase barrier; sticking;

   Sammanfattning : The thermal behaviour of palladium clusters has been investigated using Monte Carlo simulation in various ensembles. Furthermore the energy transfer between palladium clusters and rare gas atoms has been calculated in simulated collisions aiming for a calculation of the cooling of clusters in a rare gas atmosphere. LÄS MER