Our research interest lies in the broad field of computational and theoretical materials and surface science – Bridging materials science, condensed matter physics, and solid-state chemistry. In particular, we focus on these four areas of computational materials research:
Characterization and thermodynamics of surface oxides and metal surfaces
|
|
Understanding of the complex behavior of particles at surfaces requires detailed knowledge of both macroscopic and microscopic processes that take place; also certain processes depend critically on temperature, gas pressure, and chemical reservoirs (e.g. thin film growth and heterogeneous catalysis which depend sensitively on experimental preparation conditions). Through the use of extensive first-principles electronic structure theory calculations, and taking into account temperature and pressure through consideration of the chemical potential of the gas species, our group is interested in obtaining a comprehensive picture of the behavior and interaction between gases and solid metal/oxide surfaces. In addition, by coupling the use of theoretical surface spectroscopy and microscopy, we aim to provide a complete atomistic picture of surface structures to help interpret results from surface science experiments.
Selected publications:
- A. Soon, M. Todorova, B. Delley, and C. Stampfl, Oxygen adsorption and stability of surface oxides on Cu(111): A first-principles investigation, Phys. Rev. B 73, 165424 (2006) [pdf]
- C. Stampfl, A. Soon, S. Piccinin, H. Q. Shi and H. Zhang, Bridging the temperature and pressure gaps: Close-packed transition metal surfaces in an oxygen environment, J. Phys.: Conden. Matter. 20, 184021 (2008) [pdf]
- N. A. Richter, C.-E. Kim, C. Stampfl, and A. Soon, Revisiting the O/Cu(111) system – When metastable surface oxides could become an issue!, Phys. Chem. Chem. Phys. 16, 26735 (2014) [pdf, arXiv]
- T. Lee, Y. Lee, K. Kang, and A. Soon, In search of non-conventional surface oxidic motifs of Cu on Au(111), Phys. Chem. Chem. Phys. 18, 7349 (2016) [pdf]
- T. Lee, Y. Lee, S. Piccinin, and A. Soon, Ab initio thermodynamics of surface oxide structures under controlled growth conditions, J. Phys. Chem. C 121, 2228 (2017) [pdf]
Environment-dependent morphological evolution in nanoparticles
|
|
The Gibbs–Wulff theorem provides a mathematical construction that predicts the equilibrium crystal shape (ECS) of crystals or nanoparticles, whereby the total free energy of the crystal is at a minimum at a constant volume. Our group is interested to extend this thermodynamic model to describe substrate-supported nanoparticles, particularly for nanocatalysis applications, as well as (out-of-equilibrium) morphological evolution under aqueous environments.
Selected publications:
- T.-H. Lee, B. Delley, C. Stampfl, and A. Soon, Environment-dependent nanomorphology of TiN: Influence of surface vacancies, Nanoscale 4, 5183 (2012) [pdf]
- S.-H. Yoo, J.-H. Lee, B. Delley, and A. Soon, Why does bromine square palladium off? An ab initio study of brominated palladium and its nanomorphology, Phys. Chem. Chem. Phys. 16, 18570 (2014) [pdf]
- Y. Kwon, A. Soon, H. Han, and H. Lee, Shape effect of cuprous oxide particles on stability in water and photocatalytic water-splitting, J. Mater. Chem. A 3, 156 (2015) [pdf]
- S.-H. Yoo, J.-H. Lee, Y.-K. Jung, and A. Soon, Exploring stereographic surface energy maps of cubic metals via an effective pair-potential approach, Phys. Rev. B 93, 035434 (2016) [pdf]
- R. Cheula, A. Soon, and M. Maestri, Morphological changes of catalyst materials in reacting conditions by combined ab initio thermodynamics and microkinetic modelling, Catal. Sci. Technol. 8, 3493 (2018) [pdf]
Polymorphic expressions in functional ceramics
|
|
Many oxide functional ceramics can adopt a wide variety of crystal structures (i.e. polymorphic expressions), depending on the synthesis conditions. Besides the commonly reported polymorphs of these ceramics in the equilibrium phase diagram, the development of novel experimental and theoretical approaches provide a renewed interest in discovering hitherto unknown metastable polymorphs. Our group is interested in using first-principles based computational methods (including biology/nature-inspired artificial intelligence algorithms) to examine and predict new polymorphic structures of technologically-important functional ceramics, exploiting their new physiochemical properties for commercial/technological applications.
Selected publications:
- T. Lee, Y. Lee, W. Jang, and A. Soon, Understanding the advantage of hexagonal WO3 as an efficient photoanode for solar water splitting: A first-principles perspective, J. Mater. Chem. A 4, 11498 (2016) [pdf]
- Y. Lee, T. Lee, W. Jang, and A. Soon, Unraveling the intercalation chemistry of hexagonal tungsten bronze and its optical responses, Chem. Mater. 28, 4528 (2016) [pdf]
- J. Yun, W. Jang, T. Lee, Y. Lee, and A. Soon, Aligning the band structures of polymorphic molybdenum oxides and organic emitters in light-emitting diodes, Phys. Rev. Applied 7, 024025 (2017) [pdf]
- W. Jang, J. Yun, T. Lee, Y. Lee, and A. Soon, Disentangling the effects of inter- and intra-octahedral distortions on the electronic structure in binary metal trioxides, J. Phys. Chem. C 122, 3558 (2018) [pdf]
- Y.-J. Lee, T. Lee, and A. Soon, Over-stoichiometry in heavy metal oxides: The case of iono-covalent tantalum trioxides, Inorg. Chem. 57, 6057 (2018) [pdf]
Optoelectronic structure of low-dimensional nanomaterials
|
|
Low-dimensional nanoscale semiconductors exhibit clear tunable size- and shape-dependent optoelectronic properties. These nanostructures bridge the gap between small molecules and large crystals, enabling the exploitation of the useful properties of these novel nanomaterials. Our group is interested in the use of first-principles electronic structure theory to understand and design new low-dimensional nanomaterials for next-generation optoelectronic devices.
Selected publications:
- W. Jang, K. Kang, and A. Soon, Remarkably low-energy one-dimensional fault line defects in single-layered phosphorene, Nanoscale 7, 19073 (2015) [pdf, arXiv]
- W. Jang, K. Kang, and A. Soon, Acute mechano-electronic responses in twisted phosphorene nanoribbons, Nanoscale 8, 14778 (2016) [pdf]
- K. Kang, W. Jang, and A. Soon, Assembling phosphorene flexagons for 2D electron-density-guided nanopatterning and nanofabrication, Nanoscale 9, 10465 (2017) [pdf]
- A. Giri, H. Yang, K. Thiyagarajan, W. Jang, J.-M. Myoung, R. Singh, A. Soon, K. Cho, and U. Jeong, One-step solution phase growth of transition metal dichalcogenide thin films directly on solid substrates, Adv. Mater. 29, 1700291 (2017) [pdf]
- W. Jang, J. Lee, C. In, H. Choi, and A. Soon, Designing two-dimensional Dirac heterointerfaces of few-layer graphene and tetradymite-type Sb2Te3 for thermoelectric applications, ACS Appl. Mater. Interfaces 9, 42050 (2017) [pdf]