"First-principles re-investigation of bulk WO3"

Who: Hanen Hamdi, Theory Group

Place: nanoGUNE seminar room, Tolosa Hiribidea 76, Donostia - San Sebastian

Date: Monday, 20 April 2015, 11:00

Tungsten trioxide WO3 has been extensively studied because of its attractive photo-electrochromic properties that are widely used in technological applications such as smart glasses, energy-efficient windows, antiglare automobile rear-view mirrors, sunroofs, water splitting batteries, photo-anodes, etc. Most of these properties are related to a rich and complex phase diagram when cooling or doping WO3. From 1200 K down to 0K, bulk WO3 exhibits 13 structural phase transitions involving antiferroelectric, antiferrodistortive and ferroelectric structural distortions. In spite of the numerous studies, the mechanism of these phase transitions is still not fully understood and particularly the low temperature ferroelectric phase. Here we re-explore the phase diagram of bulk WO3 from first-principles calculations by using hybrid functionals (B1WC) and we show that the low temperature phases are driven by complex high order (improper) couplings between different phonon modes, which make WO3 very attracting for building multifunctional superlattices.

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