@article{15052,
  abstract     = {Substrate induces mechanical strain on perovskite devices, which can result in alterations to its lattice dynamics and thermal transport. Herein, we have performed a theoretical investigation on the anharmonic lattice dynamics and thermal property of perovskite Rb2SnBr6 and Cs2SnBr6 under strains using perturbation theory up to the fourth-order terms and the unified thermal transport theory. We demonstrate a pronounced hardening of low-frequency optical phonons as temperature increases, indicating strong lattice anharmonicity and the necessity of adopting temperature-dependent interatomic force constants in the lattice thermal conductivity (
κL) calculations. It is found that the low-lying optical phonon modes of Rb2SnBr6 are extremely soft and their phonon energies are almost strain independent, which ultimately lead to a lower 
κL and a weaker strain dependence than Cs2SnBr6. We further reveal that the strain dependence of these phonon modes in the A2XB6-type perovskites weakens as their ibrational frequency decreases. This study deepens the understanding of lattice thermal transport in perovskites A2XB6 and provides a perspective on the selection of materials that meet the expected thermal behaviors in practical applications.},
  author       = {Cheng, Ruihuan and Zeng, Zezhu and Wang, Chen and Ouyang, Niuchang and Chen, Yue},
  issn         = {2469-9969},
  journal      = {Physical Review B},
  number       = {5},
  publisher    = {American Physical Society},
  title        = {{Impact of strain-insensitive low-frequency phonon modes on lattice thermal transport in AxXB6-type perovskites}},
  doi          = {10.1103/physrevb.109.054305},
  volume       = {109},
  year         = {2024},
}

@article{14425,
  abstract     = {Water adsorption and dissociation processes on pristine low-index TiO2 interfaces are important but poorly understood outside the well-studied anatase (101) and rutile (110). To understand these, we construct three sets of machine learning potentials that are simultaneously applicable to various TiO2 surfaces, based on three density-functional-theory approximations. Here we show the water dissociation free energies on seven pristine TiO2 surfaces, and predict that anatase (100), anatase (110), rutile (001), and rutile (011) favor water dissociation, anatase (101) and rutile (100) have mostly molecular adsorption, while the simulations of rutile (110) sensitively depend on the slab thickness and molecular adsorption is preferred with thick slabs. Moreover, using an automated algorithm, we reveal that these surfaces follow different types of atomistic mechanisms for proton transfer and water dissociation: one-step, two-step, or both. These mechanisms can be rationalized based on the arrangements of water molecules on the different surfaces. Our finding thus demonstrates that the different pristine TiO2 surfaces react with water in distinct ways, and cannot be represented using just the low-energy anatase (101) and rutile (110) surfaces.},
  author       = {Zeng, Zezhu and Wodaczek, Felix and Liu, Keyang and Stein, Frederick and Hutter, Jürg and Chen, Ji and Cheng, Bingqing},
  issn         = {2041-1723},
  journal      = {Nature Communications},
  publisher    = {Springer Nature},
  title        = {{Mechanistic insight on water dissociation on pristine low-index TiO2 surfaces from machine learning molecular dynamics simulations}},
  doi          = {10.1038/s41467-023-41865-8},
  volume       = {14},
  year         = {2023},
}

@article{14605,
  abstract     = {The phonon transport mechanisms and ultralow lattice thermal conductivities (κL) in silver halide AgX (X=Cl,Br,I) compounds are not yet well understood. Herein, we study the lattice dynamics and thermal property of AgX under the framework of perturbation theory and the two-channel Wigner thermal transport model based on accurate machine learning potentials. We find that an accurate extraction of the third-order atomic force constants from largely displaced configurations is significant for the calculation of the κL of AgX, and the coherence thermal transport is also non-negligible. In AgI, however, the calculated κL still considerably overestimates the experimental values even including four-phonon scatterings. Molecular dynamics (MD) simulations using machine learning potential suggest an important role of the higher-than-fourth-order lattice anharmonicity in the low-frequency phonon linewidths of AgI at room temperature, which can be related to the simultaneous restrictions of the three- and four-phonon phase spaces. The κL of AgI calculated using MD phonon lifetimes including full-order lattice anharmonicity shows a better agreement with experiments.},
  author       = {Ouyang, Niuchang and Zeng, Zezhu and Wang, Chen and Wang, Qi and Chen, Yue},
  issn         = {2469-9969},
  journal      = {Physical Review B},
  number       = {17},
  publisher    = {American Physical Society},
  title        = {{Role of high-order lattice anharmonicity in the phonon thermal transport of silver halide AgX (X=Cl,Br, I)}},
  doi          = {10.1103/PhysRevB.108.174302},
  volume       = {108},
  year         = {2023},
}