Bulletin of the American Physical Society
2017 Annual Meeting of the APS Mid-Atlantic Section
Volume 62, Number 19
Friday–Sunday, November 3–5, 2017; Newark, New Jersey
Session N3: CMP-QM: Structural Properties |
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Chair: K.H. Ahn, New Jersey Institute of Technology Room: 215, Campus Center, NJIT |
Sunday, November 5, 2017 12:15PM - 12:51PM |
N3.00001: Structural Predictions and Dynamic Stability of Correlated Electron Materials using Embedded Dynamical Mean Field Theory Functional Approach Invited Speaker: Kristjan Haule Materials with strong electronic correlations have long resisted abinitio modeling due to their complexity arising from non-perturbative strength of the interaction. The Dynamical Mean Field Theory in combination with the Density Functional Theory has recently allowed accurate modeling of the electronic structure of many complex materials, such as the heavy fermions, transition metal oxides, iron superconductors, etc. The stationary implementation of the Dynamical Mean Field Theory functional [1] and its derivative [2] has been recently achieved, which allows one to predict forces for structural relaxation at finite temperature across the metal-insulator transition, and \textit{ab-initio} prediction of the coupling between magnetism and phonons at finite temperature. We will show how the electronic correlations enhance the electron-phonon coupling strength in FeSe[3], how the coupling of magnetism and crystal structure in rare earth nickelates leads to the metal insulator transition[4], and why is the BCC structures of elemental iron stable at high temperature[5]. \par \medskip \noindent 1. Haule, K. and Birol, T., ``Free Energy from Stationary Implementation of the $\mathrm{DFT}+\mathrm{DMFT}$ Functional''. Phys. Rev. Lett. \textbf{115}, 256402 (2015).\\ \noindent 2. Haule, K and Pascut G.L., ``Forces for structural optimizations in correlated materials within a DFT+embedded DMFT functional approach''. Phys. Rev. B \textbf{94}, 195146 (2016).\\ \noindent 3. Mandal, S. and Cohen, R.E. and Haule, K. ``Strong pressure-dependent electron-phonon coupling in FeSe''. Phys. Rev. B \textbf{89}, 220502(R) (2014).\\ \noindent 4. Haule, K. and L. G. Pascut, ``Mott Transition and Magnetism in Rare Earth Nickelates and its Fingerprint on the X-ray Scattering'', arXiv:1703.08196.\\ \noindent 5. Han, Q. and Birol, T. and Haule K. ``The phonon softening due to melting of the ferromagnetic order in elemental iron'', arXiv:1705.06877. [Preview Abstract] |
Sunday, November 5, 2017 12:51PM - 1:03PM |
N3.00002: Impact of Large Thermal Motion on Critical Properties of Perovskite Photovoltaic Systems T. A. Tyson, W. Gao, Y.-S. Chen, S. Ghose, Y. Yan To gain a fundamental understanding of their properties on an atomic level, we investigate single crystals of CH$_{\mathrm{3}}$NH$_{\mathrm{3}}$PbI$_{\mathrm{3}}$ with a narrow transition (\textasciitilde 5 K) near 327 K. We show that the ADPs for I ions yield extended flat regions in the potential wells consistent with the measured large thermal expansion parameter. We also show that the intrinsically enhanced freedom of motion of the iodine atoms enables large deformations. This flexibility (softness) of the atomic structure results in highly localized atomic relaxation about defects and hence accounts for both the high carrier mobility as well as the structural instability. [Preview Abstract] |
Sunday, November 5, 2017 1:03PM - 1:15PM |
N3.00003: Temperature Dependent Atomic Structure of LuFe$_{\mathrm{2}}$O$_{\mathrm{4}}$ Sizhan Liu, Han Zhang, Sanjit Ghose, Thomas Emge, Cherno Jaye, Daniel Fisher, Sang-Wook Cheong, Trevor Tyson The LuFe$_{\mathrm{2}}$O$_{\mathrm{4}}$ system has been studied intensively as a novel material with charge ordered driven ferroelectricity. However, the existence and origin of electric polarization and it coupling to the magnetic structure are open questions still to be addressed. We have studied the structure on LuFe$_{\mathrm{2}}$O$_{\mathrm{4}}$ on multiple length scales using X-ray diffraction, temperature and orientation dependent Raman spectroscopy, temperature dependent X-ray and neutron pair distribution function measurements and DFT modeling. The stable space groups on different length scales are being determined. This work is supported by DOE Grant DE-FG02-07ER46402. [Preview Abstract] |
Sunday, November 5, 2017 1:15PM - 1:27PM |
N3.00004: Pressure Induced Structural Phase Transitions in SrTiO$_{\mathrm{3}}$ Nanoparticles Han Zhang, Sizhan Liu, Megan Scofield, Stanislaus Wong, Xinguo Hong, Vitali Prakapenka, Eran Greenberg, Trevor Tyson Bulk SrTiO$_{\mathrm{3}}$ (STO) is paraelectric and exhibits a structural phase transition at a pressure, P\textasciitilde 6 GPa, at room temperature. However nanoscale STO is not well explored. Pressure dependent structural measurements on monodispersed nanoscale SrTiO$_{\mathrm{3}}$ samples with average diameters of 10 to \textasciitilde 80 nm were conducted to enhance the understanding of the structural phase diagram of nanoscale SrTiO$_{\mathrm{3}}$. A robust pressure independent polar structure was detected in the 10 nm sample for pressures up to 13 GPa while a size dependent cubic to tetragonal transition occurs (at P $=$ P$_{\mathrm{c}})$ for larger particle sizes. This work is supported by DOE Grant. DE-FG02-07ER46402. [Preview Abstract] |
Sunday, November 5, 2017 1:27PM - 1:39PM |
N3.00005: Implication of ferroelectric during the growth of superlattices and heterostructures Rui Liu, Alec Sun, Charles Pan, Kaize Cheng, Eli Doyle, Hsiang-Chun Hsing, Anna Gura, Giulia Bertino, Jin-Wen Lai, Matthew Dawber In ferroelectric superlattices the materials are often under considerable epitaxial strain, raising their ferroelectric transition temperature to be comparable to the growth temperature. This has important consequences for the growth of superlattices and their eventual properties. For example, the as-grown polarization domain structure in PbTiO$_{\mathrm{3}}$/BaTiO$_{\mathrm{3}}$ (PTO/BTO) superlattices is markedly different depending on if the overall structure's transition temperature lies below, above, or oscillates around the growth temperature. More surprisingly, we found that the ferroelectric polarization of a growing structure has a strong effect on the characteristics of films grown on it. We have studied this effect by focusing on the properties of BTO thin films grown on very thin layers of PTO using a combination of XRD, vertical and lateral PFM and electrical characterization. It reveals that the ferroelectricity of PTO can induce lateral polarization domain structures in BTO grown on it. Further insight into these effects is obtained by XRD performed in-situ during the growth process at the NSLS-II ISR beamline. The results show the ferroelectricity of PTO layers can effects BTO films' growth mode and help them stay in strained ferroelectric state. [Preview Abstract] |
Sunday, November 5, 2017 1:39PM - 2:15PM |
N3.00006: Understanding liquid water from first principles: a tale of two liquids. Invited Speaker: Marivi Fernandez-Serra Despite the simplicity of its molecular structure, condensed phases of water present a complicated phase diagram that has not yet been fully completed. Liquid water as we know it is not a simple liquid. The anomalies of water manifest in many thermodynamic and structural ways. Because of this the complete understanding of the phase diagram of liquid water and ice is still an active area of research in the chemical physics community. In this talk I will present how this problem can be addressed using density functional theory. Our results show that the anomalies of water are strongly linked to the coupling between vibrational and electronic degrees of freedom in the hydrogen bond interaction. And that both electronic and nuclear quantum effects will play a role in the second critical point conjecture. [Preview Abstract] |
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