Localized Soft Vibrational Modes and Coherent Structural Phase Transformations in Rutile TiO2 Nanoparticles under Negative Pressure

TY - JOUR

T1 - Localized Soft Vibrational Modes and Coherent Structural Phase Transformations in Rutile TiO2 Nanoparticles under Negative Pressure

AU - Wang, Kang

AU - Molteni, Carla

AU - Haynes, Peter D.

N1 - Funding Information: The authors thank Nava Setter (Tel Aviv University) for helpful discussions. K.W. acknowledges support from the EPSRC Centre for Doctoral Training in Theory & Simulation of Materials (EP/L015579/1). Calculations were performed at the Imperial College London Research Computing Service, the UK Materials and Molecular Modelling Hub (supported by EPSRC grants EP/P020194/1 and EP/T022213/1), and the national ARCHER2 supercomputer through the UK Car–Parrinello consortium (supported by EPSRC grants EP/P022472/1 and EP/P023118/1). We also acknowledge the Thomas Young Centre under grant number TYC-101. Data supporting this study are openly available from Zenodo at 10.5281/zenodo.6771114 . Publisher Copyright: © 2022 American Chemical Society.

PY - 2022/7/27

Y1 - 2022/7/27

N2 - We study the effect of size on the vibrational modes and frequencies of nanoparticles, by applying a newly developed, robust, and efficient first-principles-based method that we present in outline. We focus on rutile TiO2, a technologically important material whose bulk exhibits a softening of a transverse acoustic mode close to q=(12,12,14), which becomes unstable with the application of negative pressure. We demonstrate that, under these conditions, nanoparticles above a critical size exhibit unstable localized modes and we calculate their characteristic localization length and decomposition with respect to bulk phonons. We propose that such localized soft modes could initiate coherent structural phase transformations in small nanoparticles above a critical size.

AB - We study the effect of size on the vibrational modes and frequencies of nanoparticles, by applying a newly developed, robust, and efficient first-principles-based method that we present in outline. We focus on rutile TiO2, a technologically important material whose bulk exhibits a softening of a transverse acoustic mode close to q=(12,12,14), which becomes unstable with the application of negative pressure. We demonstrate that, under these conditions, nanoparticles above a critical size exhibit unstable localized modes and we calculate their characteristic localization length and decomposition with respect to bulk phonons. We propose that such localized soft modes could initiate coherent structural phase transformations in small nanoparticles above a critical size.

KW - TiO2 nanoparticles soft vibrational modes localized distortion size effect coherent structural phase transformations density functional theory

UR - http://www.scopus.com/inward/record.url?scp=85135374986&partnerID=8YFLogxK

U2 - 10.1021/acs.nanolett.2c01939

DO - 10.1021/acs.nanolett.2c01939

M3 - Article

SN - 1530-6984

VL - 22

SP - 5922

EP - 5928

JO - Nano Letters

JF - Nano Letters

IS - 14

ER -