Bachelor-PrüfungEin struktureller Phasenuebergang in BaNi2P4 und BaPd2P4 - Dimorphie durch Peierls-Verzerrung?

Datum

24.08.2015

Zeit

14:00 - 15:00

Sprecher

Elisabeth Fischer

Zugehörigkeit

TU Dresden

Sprache

en

Hauptthema

Materialien

Andere Themen

Materialien, Physik

Host

Grit Rötzer

Beschreibung

In this thesis, the structural phase transition of BaNi2P4 from an orthorhombic phase below 100^o C into a tetragonal phase is studied. Using the DFT-based program FPLO allows calculations of the ground-state electronic structure of this compound. Thereby, LDA and GGA are used to treat the exchange and correlation part of the many-particle problem. The results of both methods are compared with each other. At zero temperature, the distortion-dependant energy of the system indicates an orthorhombic phase. Increasing the temperature allows a phase transition into a tetragonal phase, which is experimentally confirmed. Within the tetragonal phase, a band-crossing is observed in the calculated band structure. Because of the Peierls distortion, this crossing splits up into two separated bands within the orthorhombic phase, lowering the density of states at the Fermi energy, which can also be observed in the Fermi surfaces and in the contributions to the density of states from the individual bands. All these effects sntrongly indicate that the presence of a Peierls distortion is responsible for the stability of the orthorhombic phase at zero temperature. In contrast to the results found for BaNi2P4, studies on structural similar BaPd2P4 revealed an extended stability of the tetragonal phase. .

Links

• Seminars at the IFW

Letztmalig verändert: 24.08.2015, 09:59:36