A mechanism of inhibition of phase transitions in nano-grained close-packed Pd thin films

0350404 - ÚFM 2011 RIV GB eng J - Journal Article
Hüger, E. - Káňa, Tomáš - Šob, Mojmír
A mechanism of inhibition of phase transitions in nano-grained close-packed Pd thin films.
Calphad - Computer Coupling of Phase Diagrams and Thermochemistry. Roč. 34, č. 4 (2010), s. 421-427. ISSN 0364-5916. E-ISSN 1873-2984
R&D Projects: GA AV ČR IAA100100920; GA MŠMT(CZ) OC10008
Institutional research plan: CEZ:AV0Z20410507
Keywords : phase transformations * thin films * nanocrystalline materials
Subject RIV: BM - Solid Matter Physics ; Magnetism
Impact factor: 1.429, year: 2010

Analyzing experimental data and calculating corresponding energy barriers from first principles, we elucidate the feasibility of the experimentally observed phase transformation between the hcp and double hcp (dhcp) structures in the hcp Pd thin films grown on W(001) and Nb(001) substrates and absence of the hcp-fcc transformation in those films. The hcp-dhcp transformation can be modeled by a transformation path which preserves the existing domain topology of the films and exhibits a sufficiently low energy barrier. On the other hand, this orthogonal pattern of rectangular domains induced by the fourfold symmetry of the substrate surface hinders the hcp Pd phase to convert back to the ground-state fcc phase, although there exists a transformation path exhibiting a very low energy barrier between the hcp and fcc structures. This path, however, would break the domain arrangement and, therefore, it cannot be accomplished. In this way, the hcp crystalline phase is locked inside of nanograins.
Permanent Link: http://hdl.handle.net/11104/0190419