Bulletin of the American Physical Society
2021 Joint Spring Meeting of the Texas Sections of APS, AAPT and Zone 13 of the SPS
Volume 66, Number 2
Thursday–Sunday, April 8–11, 2021; Virtual
Session C09: APS: Atomic and Molecular Physics-II |
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Saturday, April 10, 2021 11:00AM - 11:12AM |
C09.00001: Intramolecular $\pi $-Type Hydrogen Bonding in Cyclic Molecules Esther Ocola, Jaan Laane We have studied theoretically and experimentally the presence of intramolecular $\pi $-type hydrogen bonds in several cyclic molecules with attached OH, NH$_{\mathrm{2\thinspace }}$or SH groups to the ring. The structures of the conformers of each of the molecules were calculated, and the changes of the potential energy due to the internal rotation of the attached groups were plotted. Infrared spectroscopy and Raman spectroscopy have been used to confirm the presence of different conformers. Among the molecules which we studied are 2-indanol, 3-cyclopenten-1-ol, 2-cyclohexen-1-ol, 2-cyclopropen-1-ol, 2-cyclopropen-1-thiol, 2-cyclopropen-1-amine, and 3-cyclopenten-1-amine. For all these molecules the energy minimum was found to have an intramolecular $\pi $-hydrogen bonding. The $\pi $ bonding stabilizations range from about 2 to 10 kJ/mol. The calculated distances from the hydrogen bonded atom of the OH, NH$_{\mathrm{2}}$ or SH group to the center of the C$=$C bond of the cyclic molecule is calculated to be in the range of 2.488 {\AA} -- 2.850 {\AA} from CCSD/cc-pVTZ computations and in the range of 2.478 {\AA} and 2.740 {\AA} from MP2/cc-pVTZ computations. [Preview Abstract] |
Saturday, April 10, 2021 11:12AM - 11:24AM |
C09.00002: Lattice dynamics and stability of cubic pseudobinary Fe{\$}\textunderscore x{\$}Co{\$}\textunderscore \textbraceleft 1-x\textbraceright {\$}Ti{\$}\textunderscore \textbraceleft 0.50 Nicholas Lopez, Bethuel Khamala, Jorge Munoz NiTi is a shape-memory alloy that has a stable cubic structure at temperatures above approximately 340 K. The cubic phase of CoTi is stable above approximately 40 K, whereas the cubic FeTi is stable at all temperatures, so decreasing the number of electrons in the system stabilizes the cubic phase. In this talk we will show phonon dispersions obtained from first-principles electronic structure calculations with displaced atoms for Fe{\$}\textunderscore x{\$}Co{\$}\textunderscore \textbraceleft 1-x\textbraceright {\$}Ti{\$}\textunderscore \textbraceleft 0.50\textbraceright {\$} with compositions {\$}x $=$ \textbraceleft 0.125, 0.0625, 0.0312\textbraceright {\$}. We also looked at the effect of the Fe atoms occupying Co sites, Ti sites, and their local chemical environment. The composition Fe{\$}\textunderscore \textbraceleft 0.0625\textbraceright {\$}Co{\$}\textunderscore \textbraceleft 0.4375\textbraceright {\$}Ti{\$}\textunderscore \textbraceleft 0.50\textbraceright {\$} is at the edge of cubic stability at 0 K when the Fe atoms occupy the Co sites and are evenly distributed, but it is unstable when the occupancy is not even or the Fe occupies a Ti site. The effects can be explained using a rigid-band model when the Fe occupies Co sites, changing the number of electronic states at the Fermi level when the number of electrons in the system decreases. The occupation of the Ti sites by the Fe atoms results in more complex changes to the electronic structure, but can also be explained by a combination of decreasing charge and local atomic effects. [Preview Abstract] |
Saturday, April 10, 2021 11:24AM - 11:36AM |
C09.00003: Driven-dissipative creation of a topologically ordered state (AKLT State) Vaibhav Sharma, Erich Mueller Dissipation in an open quantum system often destroys a quantum state of interest, but if carefully engineered, it can be used as a tool to prepare interesting quantum states. We propose an experimentally viable method to dissipatively create the AKLT (Affleck-Lieb-Kennedy-Tasaki) state which exhibits symmetry protected topological order and harbours gapped edge modes. We analyze a system of bosons trapped in a tilted optical lattice, driven by coherent Raman beams and coupled to a superfluid bath. We propose a protocol under which the AKLT state emerges as the steady state. We use exact diagonalization and DMRG methods to calculate the time scale for state preparation and find that the state preparation time scales quadratically with the system size. [Preview Abstract] |
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