Vibrational Analysis of Paraelectric–Ferroelectric Transition of LiNbO3: An Ab-Initio Quantum Mechanical Treatment

Autor: Francesco Silvio Gentile, Rosita Diana, Barbara Panunzi, Ugo Caruso, Alexander Platonenko, Fabien Pascale, Roberto Dovesi
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Symmetry, Vol 13, Iss 9, p 1650 (2021)
Druh dokumentu: article
ISSN: 2073-8994
10944605
DOI: 10.3390/sym13091650
Popis: The phase transitions between paraelectric (PE) and ferroelectric (FE) isomorph phases of LiNbO3 have been investigated quantum mechanically by using a Gaussian-type basis set, the B3LYP hybrid functional and the CRYSTAL17 code. The structural, electronic and vibrational properties of the two phases are analyzed. The vibrational frequencies evaluated at the Γ point indicate that the paraelectric phase is unstable, with a complex saddle point with four negative eigenvalues. The energy scan of the A2u mode at −215 cm−1 (i215) shows a dumbbell potential with two symmetric minima. The isotopic substitution, performed on the Li and Nb atoms, allows interpretation of the nontrivial mechanism of the phase transition. The ferroelectric phase is more stable than the paraelectric one by 0.32 eV.
Databáze: Directory of Open Access Journals
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