Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 5: CE: Low-dimensional Systems - Materials 1
TT 5.8: Vortrag
Montag, 22. März 2010, 16:15–16:30, H18
Effective spin-chain model for azurite: derivation from ab-initio computations (exchanged with TT 5.9) — Ingo Opahle1, Hem C. Kandpal2, Niels Jackson1, Hena Das3, Tanusri Saha-Dasgupta3, Andreas Honecker4, •Harald O. Jeschke1, and Roser Valentí1 — 1Institut für Theoretische Physik, Goethe-Universität Frankfurt — 2IFW Dresden — 3Bose Institute, Kolkata, India — 4Institut für Theoretische Physik, Universität Göttingen
The observation of complex spin dynamics and a 1/3 magnetization plateau has revived the interest in the famous pigment azurite Cu3(CO3)2(OH)2. We revisit the question of the underlying microscopic Hamiltonian using a combination of first principles methods. As a guiding tool, we employ NMTO downfolding which yields the relative importance at low energies of the many possible hybridization paths between the copper centers. In order to obtain the corresponding exchange coupling strengths we perform total energy calculations for many spin configurations and several supercells. We employ FPLAPW and FPLO basis sets with LDA+U functionals, and we investigate the dependence of the exchange couplings on the correlation strength U. We find that the low-energy Hamiltonian of azurite is a diamond chain with a monomer-monomer coupling and some nonzero interchain couplings. We show that the neglect of interchain couplings effectively leads to a less symmetric diamond chain.