Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session S02: Developments of DFT: from Quantum to Statistical Mechanics (VI)Focus

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Sponsoring Units: DCP DCOMP GSNP Chair: Neepa Maitra, Hunter Coll Room: LACC 150B 
Thursday, March 8, 2018 11:15AM  11:51AM 
S02.00001: Nonadiabatic dynamics on a single timedependent potential energy surface Invited Speaker: Eberhard K Gross Some of the most fascinating quantum phenomena, such as the process of vision or phonondriven superconductivity are examples of nonadiabatic dynamics where more than one BornOppenheimer surface is involved. To tackle such situations one has to face the full Hamiltonian of the complete system of electrons and nuclei. We deduce an exact factorization [Abedi, Maitra, Gross, PRL 105, 123002 (2010)] of the full electronnuclear wavefunction into a purely nuclear part and a manyelectron wavefunction which parametrically depends on the nuclear configuration and carries the meaning of a conditional probability amplitude. The equations of motion for these wavefunctions uniquely define the exact potential energy surface and the exact geometric phase, both in the timedependent and in the stationary regime. We discuss a case where the exact Berry phase vanishes although there is a nontrivial Berry phase for the same system in BornOppenheimer approximation, implying that in this particular case the BornOppenheimer Berry phase is an artifact [Min, Abedi, Kim, Gross, PRL 113, 263004 (2014)]. In the timedomain, whenever there is a splitting of the nuclear wavepacket in the vicinity of an avoided crossing, the exact timedependent surface shows a nearly discontinuous, moving step [Abedi, Agostini, Suzuki, Gross, PRL 110, 263001 (2013)] between adiabatic surfaces, reminiscent of Tully surface hopping. Based on this observation, we propose novel mixedquantumclassical algorithms which provide a much improved (over surface hopping) description of decoherence [Min, Agostini, Gross, PRL 115, 073001 (2015)]. This is demonstrated for the laserinduced ring opening of the oxirane molecule [Min, Agostini, Tavernelli, Gross, JPCL 8, 3048 (2017)]. We present a multicomponent density functional theory based on the exact factorization that provides an avenue to make the fully coupled electronnuclear system tractable also for large systems [Requist, Gross, PRL 117, 193001 (2016)]. 
Thursday, March 8, 2018 11:51AM  12:03PM 
S02.00002: GloballyOptimized Local Pseudopotentials for (OrbitalFree) Density Functional Theory Simulations of Liquids and Solids Beatriz Gonzalez del Rio, Johannes Dieterich, Emily Carter Orbitalfree density functional theory (OFDFT) is a promising technique for accurate, largescale, quantum simulations. One key element determining the fidelity of OFDFT is the need to use local pseudopotentials (LPSs) to describe electronion interactions. We developed a global optimization strategy for LPSs that enables OFDFT to reproduce solid and liquid properties obtained from KohnSham DFT, resulting in globally optimized LPSs (goLPSs) that can be used in solid and/or liquidphase simulations, depending on the fitting process.^{1} Moreover, we can improve the initial transferability of goLPSs by fitting to the deltagauge^{2} and the valence electron density in the solid phases. A variety of test cases show that we can (1) improve solid properties compared to our previous bulkderived LPS generation scheme; (2) refine predicted liquid and solid properties, as well as phase transition temperatures, by adding forcematching data; and (3) generate accurate goLPSs directly from the local channel of nonlocal pseudopotentials. We also will introduce the new goLPS library available. 
Thursday, March 8, 2018 12:03PM  12:15PM 
S02.00003: van Leeuwen Theorem for Mixed States and Finite Temperature Density Response James Dufty, Kai Luo, Sam Trickey A simple proof of the van Leeuwen theorem for existence and uniqueness of vrepresentability in finitetemperature timedependent density functional theory is described. It is used to construct the linear density response function for a system of electrons in a random configuration of ions, in terms of its corresponding noninteracting form. The relevance of this for justifying the KuboGreenwood model for transport properties in warm, dense matter, and its context, is described. The density response function in the "adiabatic approximation" is shown to be the same as that from a recent exact short time kinetic theory [1]. This provides a further characterization of that approximation, and makes connection to the manybody methods of kinetic theory. 1. On the KuboGreenwood Model for Electron Conductivity, J. Dufty, J. Wrighton, K. Luo, and S. Trickey, submitted to Contr. Plasma Phys., arXiv:1709.04732. 
Thursday, March 8, 2018 12:15PM  12:27PM 
S02.00004: Evenhanded subsystem selection in projectionbased wavefunctioninDFT embedding Matthew Welborn, Thomas Miller Projectionbased embedding offers a simple framework for embedding wavefunction theories in density functional theory. Underlying this embedding is a heuristic for translating the chemicallyintuitive idea of a set of embedded atoms into a set of embedded orbitals on which the wavefunction calculation will be performed. For singlepoint energy calculations, a successful heuristic has been to first localize the occupied KohnSham orbitals, and then assign these localized orbitals to the embedded region based on atomic population analysis. However, for chemical reactions involving large geometry changes, the nature of the localized orbitalsâ€”as well as their atomic populationsâ€”can change dramatically. This can lead to qualitatively different embedded orbitals between geometries, resulting in unphysical cusps and even discontinuities in the potential energy surface. In this talk, we present an evenhanded framework for localized orbital partitioning that ensures invariance of the span of the embedded orbitals throughout a geometry coordinate. We illustrate this problem and its solution with a simple example of an SN2 reaction. We then apply our method to a nitrogen umbrella flip in a cobaltbased CO2 reduction catalyst and to the binding of CO to a Cu(111) surface. 
Thursday, March 8, 2018 12:27PM  12:39PM 
S02.00005: A study of accurate exchangecorrelation functionals through adiabatic connection Manoj Harbola, Rabeet Singh A systematic way of improving exchangecorrelation energy functionals of density functional theory has been to make them satisfy more and more exact relations. Starting from the initial GGA functionals, this has culminated into the recently proposed SCAN(Strongly constrained and appropriately normed) functional that satisfies several known constraints and is appropriately normed. The ultimate test for the functionals developed is the accuracy of energy calculated by employing them. In this paper, we test these exchangecorrelation functionals  the GGA hybrid functionals B3LYP and PBE0, and the metaGGA functional SCAN  from a different perspective. We study how accurately these functionals reproduce the exchangecorrelation energy when electronelectron interaction is scaled as Vee with varying between 0 and 1. Our study reveals interesting comparison between these functionals and the associated difference Tc between the interacting and the noninteracting kinetic energy for the same density. 
Thursday, March 8, 2018 12:39PM  12:51PM 
S02.00006: Development of Effective Stochastic KohnSham Potential Method using Random Matrix Theory for Performing DFT Calculations on Noisy Chemical Systems Arindam Chakraborty In this work, we present the effective stochastic KohnSham (ESKS) potential method to address the fundamental question of the impact of fluctuations in the external potential in the KSDFT formulation. The functional relationship between the external potential and the electron density is central to the DFT formulation. Need for efficient treatment fluctuations in the external potential arises in chemical systems because of the presence of solvents and the existence of nonzero temperatures. We introduce the concept of a deformation potential and demonstrate its existence by the proofbyconstruction approach. A statistical description of the fluctuations in the deformation potential due to nonzero temperature was obtained using infiniteorder moment expansion of the distribution. The formal mathematical definition of the effective stochastic KohnSham potential was derived using functional minimization approach to match the infiniteorder moment expansion for the deformation potential. Practical implementation of the ESKS was obtained using the randommatrix theory method. The developed method was applied for calculations of the distribution of energies and quasiparticle gaps in atoms, molecules, and solvated quantum dots at nonzero temperatures. 
Thursday, March 8, 2018 12:51PM  1:03PM 
S02.00007: Strong correlation in timedependent density functional theory Kieron Burke, Diego Carrascal, Jaime Ferrer, Neepa Maitra The asymmetric Hubbard dimer is used to study the densitydependence of the exact frequency dependent kernel of linearresponse timedependent density functional theory (TDDFT). The exact form of the kernel is given, and the limitations of the adiabatic approximation utilizing the exact groundstate functional are shown. A generalization of the doubleexcitation kernel of dressed TDDFT is derived for this situation, and shown to be accurate in the weakcorrelation regime. A simple interpolation of the kernel between carefully defined weakcorrelation and strongcorrelation regimes yields accurate transition frequencies for both the single and double excitations, including chargetransfer excitations. A general definition of multiple excitations is given. Oscillator strengths are defined appropriately for lattice Hamiltonians. The exact fluctuationdissipation formula for the groundstate XC energy for the dimer is given. 
Thursday, March 8, 2018 1:03PM  1:15PM 
S02.00008: Fluctuations in densityfunctional theory for fluids: Theory and computations Miguel Angel DuranOlivencia, Petr Yatsyshin, Antonio Russo, Serafim Kalliadasis Classical densityfunctional theory (DFT) for fluids and its dynamic extension (DDFT) provide an appealing meanfield framework for describing equilibrium and dynamics of complex soft matter systems. For a long time, accounting for the effects of thermal fluctuations under this theoretical framework was thought to be impossible, if not fundamentally incorrect. Here, we present an abinitio derivation of a fluctuating DDFT (FDDFT) where thermal fluctuations are derived from first principles, thus advancing the longstanding debate about the inclusion of fluctuations. As a byproduct, we obtain a nonequilibrium energy functional which recovers the Helmholtz free energy under equilibrium conditions. We show that there is a onetoone connection between our FDDFT formalism and the phenomenological LandauLifshitz fluctuating hydrodynamics. To showcase the potential and computational capacity of the formalism developed in this work, we apply it to the study of homogeneous nucleation, a classical problem considered to be outside the limits of applicability of DFT. Finally, we highlight how our theoretical effort can open the door to the discovery of new physical laws governing the dynamics of softmatter systems outofequilibrium and under noisedominated conditions. 
Thursday, March 8, 2018 1:15PM  1:27PM 
S02.00009: Understanding interfacial wetting transitions with classical density functional theory Petr Yatsyshin, Miguel Angel DuranOlivencia, Andrew Parry, Carlos Rascon, Serafim Kalliadasis Interfaces provide valuable insights into the workings of the atomic world. In problems of wetting, where often a liquidgas interface is in contact with a solid substrate, the width and position of the gasliquid interface depend strongly on the range of interparticle potentials. A satisfactory description of wetting can be achieved by classical densityfunctional theory (DFT), a fully microscopic approach, capturing the smallscale behavior of matter, as well as the inherently nonlocal nature of interparticle interactions. In this talk, we apply classical DFT to investigate smallscale surface phase transitions in a wide spectrum of physical settings with emphasis on wetting on heterogeneous planar substrates. We compute wetting isotherms, locating hystereses and the jumps in adsorption, wetting temperatures and interface binding potentials (disjoining pressure). Our results may have important ramifications for the design of labonachip devices, superhydrophobic surfaces, and controlled micro/nanofluidics. 
Thursday, March 8, 2018 1:27PM  1:39PM 
S02.00010: Zeropoint motion of molecules: beyond BornOppenheimer Grigory Kolesov, Efthimios Kaxiras, Efstratios Manousakis We have recently developed a new timedependent densityfunctional theory (TDDFT)based nonBornOppenheimer method for computing electronion structure of atomistic systems in the path integral formalism. We discuss our implementation of this exact (within the accuracy of DFT) method with a localized basis set approach. The method and the implementation can be used for both molecules and solids. First we apply this method to compute electronion states and zeropoint energies of small molecules. Next we compare the results of these computations to results obtained from the standard (BornOppeheimerbased) pathintegral methods used in the field. We demonstrate that at low temperatures the error of the standard pathintegral approaches is large even for the systems with wide bandgaps. We discuss potential areas of applicability of our method. 
Thursday, March 8, 2018 1:39PM  1:51PM 
S02.00011: Efficient Implementation of the Approximate Exchange Kernel Method Guo Chen, Matthew Agee, Filipp Furche The approximate exchange kernel (AXK) method is the leading correction to the randomphase approximation (RPA) for the groundstate correlation energy functional within RPArenormalized manybody perturbation theory. AXK alleviates the unphysical shortrange behavior of RPA and improves the prediction of energetics for processes that do not conserve the number of electron pairs. However, the relatively high computational cost of AXK has hampered its widespread application in the past. Here we present a fast AXK algorithm with O(N^{4}lnN) scaling. The algorithm takes advantage of the resolutionoftheidentity (RI) approximation and imaginary frequency integration technique. The new RIAXK implementation in TURBOMOLE enables correlation energy calculations for molecules with well over 100 atoms on a single cluster node. 
Thursday, March 8, 2018 1:51PM  2:03PM 
S02.00012: The SCAN MetaGGA : An Efficient Universal NonEmpirical Semilocal Density Functional Jianwei Sun The accuracy of the KohnSham density functional theory is limited by the approximation to its exchangecorrelation energy E_{xc}. Due to the computational efficiency of semilocal approximations that use as inputs only the electron density, its gradient, and the kinetic energy density, efforts are still made to improve the PBE GGA, the standard nonempirical semilocal density functional that is robust and universally applicable to different systems. Semilocal approximations are also bases for developing nonlocal density functionals that are needed for treating longrange effects (e.g., the van der Waals interaction and charge transfer), which further motivates such efforts. The SCAN semilocal density functional, the most sophisticated one so far [1] with systematic improvement over PBE with a comparable computational efficiency[2], represents a successful example of these efforts. Here, SCAN is further tested and gives promising performance on two difficult properties: the ground structure selections of about 300 binary solids and the metalinsulatortransition of a cuprate under doping. 
Thursday, March 8, 2018 2:03PM  2:15PM 
S02.00013: A Novel Generalized Gradient Approximation for the Noninteracting Kinetic Energy Density Functional Kai Luo, Valentin Karasiev, Sam Trickey Reliable and accurate approximation of the noninteracting kinetic 
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