Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session F53: DCP Plyler and Jankunis Prize SessionFocus
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Sponsoring Units: DCP Chair: David Nesbitt, University of Colorado, Boulder Room: Hilton Baltimore Holiday Ballroom 4 |
Tuesday, March 15, 2016 11:15AM - 11:51AM |
F53.00001: Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics: Photochemistry of Phenol: A Full-Dimensional Semiclassical Simulation Invited Speaker: Donald Truhlar ~This lecture will present a simulation of the photodissociation of phenol that is made possible by combining four methods in a complementary way: (1) the fourfold way for generating diabatic electronic states, based on diabatic molecular orbitals and configurational uniformity; (2) anchor points reactive potentials for fitting the 33-dimensional diabatic potentials; (3) coherent switches with decay of mixing for multistate dynamics governed by coupled potential energy surfaces, including density matrix coherence and decoherence; (4) army ants tunneling, including electronically nonadiabatic tunneling. By combining all these methods, one can thoroughly sample an ensemble of trajectories with potential energy surfaces and couplings that include multireference dynamic electron correlation. By including army ants tunneling, the trajectory simulation of phenol photodissociation dynamics based on accurate full-dimensional anchor-points reactive potential surfaces and state couplings successfully reproduces the experimentally observed bimodal total kinetic energy release spectra. Analysis of the trajectories uncovers an unexpected dissociation pathway. The new method for including tunneling in full-dimensional molecular dynamics simulations is general, and it can also be used for electronically adiabatic processes. [Preview Abstract] |
Tuesday, March 15, 2016 11:51AM - 12:27PM |
F53.00002: Jankunas Doctoral Dissertation Award: Attosecond science with recolliding electrons Invited Speaker: Peter Kraus Measuring the motion of valenceshell electrons in molecules is one of the main research thrusts in modern ultrafast science. The process of highharmonic generation (HHG), the conversion of many infrared photons into one XUV photon, relies on the laserdriven ionization, acceleration and precisely timed recombination in a strong laser field. The frequencies emitted upon recollision can be uniquely mapped to a transit time of the electron in the continuum thus providing attosecond temporal and Angstrom spatial resolution encoded in the HHG spectrum. In this talk we present experiments that utilize these capacities of HHG for following a coherent valenceshell electron current in nitric oxide on the femtosecond time scale in a classical pumpprobe experiment. Furthermore, we use the intrinsic time resolution of the HHG process to measure attosecond timescale electron dynamics: The motion of an electron hole across a molecular chain after ionization in spatially oriented iodoacetylene molecules. [Preview Abstract] |
Tuesday, March 15, 2016 12:27PM - 1:03PM |
F53.00003: Multi-Configuration Pair-Density Functional Theory Invited Speaker: Laura Gagliardi We have recently developed a new theoretical framework, called Multiconfiguration Pair-Density Functional Theory (MC-PDFT),[1] which combines multiconfigurational wave functions with a generalization of density functional theory (DFT). In this talk I will describe the basic principles of the theory and I present our latest results with MC-PDFT on spectroscopy,[2] charge-transfer systems[3] and molecules containing transition metals[4]. \\ \\$[1]$ G. Li Manni, R. K. Carlson, S. Luo, D. Ma, J. Olsen, D. G. Truhlar, and\underline { L. Gagliardi}, Multi-Configuration Pair-Density Functional Theory, \underline {\textit{J. Chem. Theory Comput.,}} \textbf{10 (9), 2014 }pp 3669-3690 \\ \\$[2]$ C. E. Hoyer, \underline {L. Gagliardi}, and D. G. Truhlar, Multiconfiguration Pair-Density Functional Theory Spectral Calculations Are Stable to Adding Diffuse Basis Functions, \underline {\textit{J. Phys. Chem. Lett.}}, \textbf{(6), 2015}, pp 4184--4188 \\ \\$[3]$ S. Ghosh, A. L. Sonnenberger, C. E. Hoyer, D. G. Truhlar, and \underline {L. Gagliardi}, Multiconfiguration Pair-Density Functional Theory Outperforms Kohn--Sham Density Functional Theory and Multireference Perturbation Theory for Ground-State and Excited-State Charge Transfer, \underline {\textit{J. Chem. Theory Comput.}}, \textbf{11 (8), 2015}, pp 3643-3649 \\ \\$[4]$ R. K. Carlson, D. G. Truhlar, and \underline {L. Gagliardi}, Multiconfiguration Pair-Density Functional Theory: A Fully Translated Gradient Approximation and Its Performance for Transition Metal Dimers and the Spectroscopy of Re$_{\mathrm{2}}$Cl$_{\mathrm{8}}^{\mathrm{2-}}$, \underline {\textit{J. Chem. Theory Comput.}}, \textbf{11 (9), 2015}, pp 4077-4085 [Preview Abstract] |
Tuesday, March 15, 2016 1:03PM - 1:15PM |
F53.00004: MN15-L and MN-15: New Kohn-Sham Density Functionals with Board Accuracy for Main-Group and Transition Metal Chemistry and Noncovalent Interactions Haoyu Yu, Xiao He, Donald G. Truhlar The accuracy of Kohn-Sham density functional theory depends on the exchange-correlation functional. Local functionals depending on only the density ($\rho )$, density gradient (grad), and possibly kinetic energy density ($\tau )$ have been popular because of their low cost and simplicity, but the most successful functionals for chemistry have involved nonlocal Hartree-Fock exchange (hybrid functionals). We have designed a new meta gradient approximation called MN15-L and a new hybrid meta gradient approximation called MN15 and tested them systematically for 17 absolute atomic energies, 51 noncovalent interaction energies, 56 data on transition metal atoms and molecules, and for 298 other atomic and molecular energetic data, including main-group and transition metal bond energies, ionization potentials, proton affinities, reaction barrier heights, hydrocarbon thermochemistry, excitation energies, and isomerization energies. When compared with 84 previous density MN15 and MN15-L give respectively the smallest and second smallest mean unsigned errors (MUEs, in kcal/mol) on all 422 data with errors for the 4 subsets above being: MN15: 6, 0.26, 4.4, 1.6; MN15-L: 7, 0.45, 4.3, 2.0. Third best: M06: 4, 0.35, 7.7, 2.2. Best previous local functional: M06-L: 7, 0.42, 6.0, 3.5. Other popular functionals: B3LYP: 18, 0.82, 8.2, 4.3; HSE06: 33, 0.58, 8.8, 3.6; TPSS: 18, 0.89, 7.25, 5.0; PBE, 47, 0.88, 9.1, 6.0. MN15-L also performs well for solid-state cohesive energies. [Preview Abstract] |
Tuesday, March 15, 2016 1:15PM - 1:27PM |
F53.00005: Density functionals from deep learning Jeffrey McMahon Density-functional theory is a formally exact description of a many-body quantum system in terms of its density; in practice, however, approximations to the universal density functional (DF) are necessary. Machine learning has recently been proposed as a novel approach to discover such a DF (or components of it)\footnote{J.\ C.\ Snyder, M.\ Rupp, K.\ Hansen, K.-R.\ M\"uller, and K.\ Burke, \textit{Phys. Rev. Lett.} \textbf{108}, 253002 (2012).}. Conventional machine learning algorithms, however, are limited in their ability to process data in their raw form, leading to invariance and/or sensitivity issues. In this presentation, an alternative approach based on deep learning will be demonstrated\footnote{J.\ M.\ McMahon, \textit{Submitted} (2015).}. Deep learning allows computational models that are capable of discovering intricate structure in large and/or high-dimensional data sets with multiple levels of abstraction, and do not suffer from the aforementioned issues. Results from the application of this approach to the prediction of the kinetic-energy DF of noninteracting electrons will be presented. Using theoretical results from computer science, a connection between the underlying model and the theorems of Hohenberg and Kohn will also be suggested. [Preview Abstract] |
Tuesday, March 15, 2016 1:27PM - 1:39PM |
F53.00006: Enhancing Linear-Scaling DFT for Extended Systems via a QM/QM Fragment Approach Laura Ratcliff, Luigi Genovese, Stephan Mohr, Thierry Deutsch We recently introduced a minimal basis approach to the wavelet-based BigDFT code, wherein a minimal set of localized support functions are expressed in an underlying wavelet basis and optimized to reflect their chemical environment. This not only forms the basis of an accurate linear-scaling DFT approach, allowing systems of 10,000 atoms or more to be treated with modest computational resources, but also facilitates the straightforward definition of a fragment approach. Such an approach can reduce the computational cost by an order of magnitude while also offering additional flexibility. We have previously demonstrated the suitability of a molecular fragment approach for the treatment of environmental effects within the context of constrained DFT and have now also expanded the method to include the treatment of extended, periodic systems. In this talk we will describe the extended fragment approach and present examples of its application to large defect systems, as well as offering a perspective on future directions for the treatment of very large systems, such as an embedded approach. [Preview Abstract] |
Tuesday, March 15, 2016 1:39PM - 1:51PM |
F53.00007: Complex wet-environments in electronic-structure calculations Giuseppe Fisicaro, Luigi Genovese, Oliviero Andreussi, Nicola Marzari, Stefan Goedecker The computational study of chemical reactions in complex, wet environments is critical for applications in many fields. It is often essential to study chemical reactions in the presence of an applied electrochemical potentials, including complex electrostatic screening coming from the solvent. In the present work we present a solver to handle both the Generalized Poisson and the Poisson-Boltzmann equation. A preconditioned conjugate gradient (PCG) method has been implemented for the Generalized Poisson and the linear regime of the Poisson-Boltzmann, allowing to solve iteratively the minimization problem with some ten iterations. On the other hand, a self-consistent procedure enables us to solve the Poisson-Boltzmann problem. The algorithms take advantage of a preconditioning procedure based on the BigDFT Poisson solver for the standard Poisson equation. They exhibit very high accuracy and parallel efficiency, and allow different boundary conditions, including surfaces. The solver has been integrated into the BigDFT and Quantum-ESPRESSO electronic-structure packages and it will be released as a independent program, suitable for integration in other codes. We present test calculations for large proteins to demonstrate efficiency and performances. [Preview Abstract] |
Tuesday, March 15, 2016 1:51PM - 2:03PM |
F53.00008: Investigating the Self-assembled Structure of Polycyclic Aromatic Hydrocarbons Using Two Dimensional Infrared Spectroscopy Jenee D. Cyran, Amber T. Krummel Self-assembly mechanisms are required for many biological and material processes, such as chlorophyll in photosynthesis, the tobacco mosaic virus and in the formation of molecular crystals. The self-assembly process can be favorable in the case of formation of nanoparticles for electronic devices. However, self-assembly processes, such as asphaltene nanoaggregation, can be unwarranted. Studying the structure of self-assembled supramolecules is important to understand how to mimic or inhibit the formation of the nanoaggregates. In this research, we studied the monomer and self-assembled structure of two polycyclic aromatic hydrocarbons (PAHs), lumogen orange and violanthrone-79, using two-dimensional infrared spectroscopy (2D IR). The carbonyl stretching and the ring breathing vibrational modes were used as vibrational probes. For violanthrone-79, a local mode basis and an electrostatic coupling model were applied to three nanoaggregate structures; parallel, antiparallel, and 28 degrees rotation. The experimental and simulated 2D IR spectra are best represented by majority of the antiparallel configuration with some angular distribution. For lumogen orange, vibrational cross peaks appear as the concentration is increased from a monomer to a nanoaggregate. The 2D IR cross peaks indicate vibrational coupling, which relates directly to the nanoaggregate structure. Comparison between the self-assembled structure of lumogen orange and violanthrone-79 can determine the role of side chains in the nanoaggregate structure. [Preview Abstract] |
Tuesday, March 15, 2016 2:03PM - 2:15PM |
F53.00009: Reversible electro-strain coupling in K-doped BaTiO$_3$ Shi Liu, Ronald E. Cohen Ferroelectric materials that possess a spontaneous polarization have a wide range of applications. Coupled with a non-180$^{\circ}$ polarization switching, the strain of a ferroelectric crystal will change, due to the exchange of nonequal crystallographic axes. The field-induced large electro-strain coupling accompanied by non-180$^{\circ}$ domain switching, however, is usually an one-time effect, because the system lacks the driving force to recover to its original state, thus limiting its usefulness. It is suggested that defect dipoles introduced by dopant-vacancy pairs could serve as the driving force for reversible domain switching. However, there is still a lack of first-principles-supported microscopic understanding of the role of defect dipoles in reversible domain switching. In this work, we explore the intrinsic effects of K-dopants and oxygen vacancy on the 90$^{\circ}$ polarization switching in the prototypical ferroelectric BaTiO$_3$ with density functional theory. The interplay between polar defect dipole, vacancy concentration and electromechanical properties is investigated. We find that defect dipoles could drive the system back to its original state spontaneously after the electric field is turned off. [Preview Abstract] |
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