Ca2MnO4 structural path: Following the negative thermal expansion at the local scale
| Autor: | G.N.P. Oliveira, I. P. Miranda, Antonio M. dos Santos, João P. Araújo, J. G. Correia, Tiago Leal, Helena M. Petrilli, Armandina M. L. Lopes, Pedro Rocha-Rodrigues, Lucy V. C. Assali, Samuel S. M. Santos |
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| Rok vydání: | 2020 |
| Předmět: |
Physics
Diffraction Path following Local scale Order (ring theory) 02 engineering and technology Atmospheric temperature range 021001 nanoscience & nanotechnology 01 natural sciences Crystallography Octahedron Negative thermal expansion Ab initio quantum chemistry methods 0103 physical sciences 010306 general physics 0210 nano-technology |
| Zdroj: | Physical Review B. 102 |
| ISSN: | 2469-9969 2469-9950 |
| DOI: | 10.1103/physrevb.102.104115 |
| Popis: | The oxygen octahedral rotations in ${\mathrm{Ca}}_{2}\mathrm{Mn}{\mathrm{O}}_{4}$, the first member of the $\mathrm{Ca}\mathrm{O}{({\mathrm{CaMnO}}_{3})}_{n}$ Ruddlesden-Popper family, is probed through a set of complementary techniques, including temperature-dependent neutron and x-ray diffraction, combined with local probe studies and ab initio calculations. Here we demonstrate the enhancement of the uniaxial negative thermal expansion coefficient from $\ensuremath{-}1.26\ifmmode\pm\else\textpm\fi{}0.25$ to $\ensuremath{-}21\ifmmode\pm\else\textpm\fi{}1.8$ ppm/K at the second order $I{4}_{1}/acd$ to $I4/mmm$ structural phase transition, providing direct evidence for the corkscrew atomic mechanism. We establish, also, that the predicted $I4/mmm$ high symmetry is attained around 1050 K. At lower temperatures, within the 10--1000 K temperature range, our first-principles calculations and detailed analysis of the Ca local environment reveals that the reported $Aba2$ structural phase, coexisting with the $I{4}_{1}/acd$ one, cannot describe correctly this compound. On the other hand, our data allow for the coexistence of the locally identical $I{4}_{1}/acd$ and $Acam$ structural phases. |
| Databáze: | OpenAIRE |
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