On the crystal energy and structure of A{sub 2}Ti{sub n}O{sub 2n+1} (A=Li, Na, K) titanates by DFT calculations and neutron diffraction
- Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, 20125 Milano (Italy)
- ISIS Facility, CCLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX (United Kingdom)
First-principles quantum-mechanical calculations (CRYSTAL09 code, B3LYP functional) were performed on alkali titanates A{sub 2}Ti{sub n}O{sub 2n+1} with layered structure (n=3,4,6). Monoclinic structural types with unshifted (P2{sub 1}/m) and with shifted (C2/m) layers were considered. Crystal energies and full structural details were obtained for all Li, Na, and K phases. Neutron diffraction data were collected on powder samples of P2{sub 1}/m-Li{sub 2}Ti{sub 3}O{sub 7} (a=9.3146(3), b=3.7522(1), c=7.5447(3) Å, β=97.611(4)°) and C2/m-K{sub 2}Ti{sub 4}O{sub 9} (a=18.2578(8), b=3.79160(9), c=12.0242(4) Å, β=106.459(4)°) and their structures were Rietveld-refined. Computed energies show the P2{sub 1}/m arrangement as favoured over the C2/m one for n=3, and the opposite holds for n=6. In the n=4 case the P2{sub 1}/m configuration is predicted to be more stable for Li and Na, and the C2/m one for K titanates. Analysis of Li–O and K–O crystal-chemical environments from experiment and theory shows that the alkali atom bonding is stabilized/destabilized in the different phases consistently with the energy trend. - Graphical abstract: Display Omitted - Highlights: • The P2{sub 1}/m structure-type is found to be more stable for A{sub 2}Ti{sub 3}O{sub 7} layer titanates. • The C2/m structure-type is found to be more stable for A{sub 2}Ti{sub 6}O{sub 13} layer titanates. • Tetratitanates are predicted to prefer the P2{sub 1}/m (Li and Na) or C2/m (K) structure. • Li–O and K–O bond distances follow a trend consistent with computed phase energies.
- OSTI ID:
- 22274071
- Journal Information:
- Journal of Solid State Chemistry, Vol. 205; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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