Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session G58: DFT and Beyond VFocus
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Sponsoring Units: DCP DCOMP DPOLY DCMP Chair: Carsten Ullrich, Univ of Missouri - Columbia Room: Mile High Ballroom 3B |
Tuesday, March 3, 2020 11:15AM - 11:51AM |
G58.00001: Structural effects on excitonic interactions in functional materials from first principles Invited Speaker: Sivan Refaely-Abramson Optical and excited-state phenomena are key ingredients in functional materials characterization, dominating emerging applications in broad areas of photophysics. Excited-state properties, including linear and non-linear light absorption, as well as radiative and non-radiative exciton decay processes, are strongly related to the material structure and composition. Recent experimental advances allow a controlled fabrication of structurally complex materials, along with close tracking of excited-state processes in them. However, a theoretical realization of the underlying interactions and subsequent design rules in such materials is highly challenging, as it demands a predictive description of the involved excitations, strongly depending on the structural perturbation. In this talk, I will describe a computational assessment of the relation between excitonic phenomena and material structure and design, using many-body perturbation theory within the GW and Bethe-Salpeter equation (GW-BSE) approach. I will discuss the effect of atomic defects and heterostructures on the excitonic properties in layered transition metal dichalcogenides (TMDs), where the structural complexity leads to mixed transitions between states of different nature and localization, determining unique and tunable selection rules and absorption. I will further present a GW-BSE-based approach to study exciton transport with relation to material structure and symmetry, demonstrated on selected systems of varying dimensionalities. |
Tuesday, March 3, 2020 11:51AM - 12:03PM |
G58.00002: The Accuracy of a Tuned Screened Range-Separated Hybrid DFT for Describing Electronic and Optical Properties of Defective Semiconductors Kirk Lewis, Ashwin Ramasubramaniam, Sahar Sharifzadeh Many-body perturbation theory (MBPT) has emerged as a state-of-the-art approach for quantitatively accurate prediction of (opto)electronic properties of materials. However, the computational cost of MBPT motivates the search for simpler methods, particularly those based on density functional theory (DFT), to enable the study of larger and more complex systems. In particular, tuned and screened range-separated hybrid (SRSH) hybrid methods have been shown to provide MBPT accuracy at the cost of hybrid DFT for many materials. We test the accuracy of time-dependent (TD)SRSH for describing the optoelectronic properties of defective semiconductors by the study of point defects in bulk GaN. We first show that the predicted quasiparticle gap and low-energy excitation spectra of (TD)SRSH and MBPT agree well in pristine GaN and GaN containing a single nitrogen vacancy, establishing the accuracy of the method. Aided by the reduced computational cost of (TD)SRSH, we then report on a series of technologically relevant point defects in GaN. This study indicates that TDSRSH is a computationally feasible approach for quantitatively accurate first-principles modeling of defective semiconductors. |
Tuesday, March 3, 2020 12:03PM - 12:15PM |
G58.00003: UNDERSTANDING EXCITONS IN STACKED PERYLENE DIIMIDE DERIVATIVES Aliya Mukazhanova, Kasidet Jing Trerayapiwat, Sahar Sharifzadeh π-stacked organic chromophores are promising class of materials for optoelectronics with their electronic properties strongly dependent on the chemical structure of the molecule and inter-molecular interactions. Here, we investigate the optical properties of recently synthesized stacked perylene diimide derivatives via time-dependent density functional theory with a Franck-Condon Herzberg-Teller approximation of vibronic effects, validating our approach by comparison to measurement. By stacking the molecules along a DNA-like backbone and varying the number of stacked molecules from one to three, we determine the role of inter- and intra- molecular interactions on the nature of optical excitations. We determine that for stacked molecules, ground-state vibrational excitations play an important role in the optical absorption spectrum, which we account for via molecular dynamics. Additionally, we apply a nonadiabtic dynamics method to study the role of the backbone on evolution of excited-states. We demonstrate that inter-molecular interactions and backbone strongly influence optical properties, providing new design strategies for efficient optoelectronic materials. |
Tuesday, March 3, 2020 12:15PM - 12:27PM |
G58.00004: First-principles investigations of structure and vibrations of c(4x2) PF3 on Cu(001) Nima Karimitari, Steven Lewis We use first-principles density functional theory(DFT) to study the structure and vibrational dynamics of PF3 on the Cu(001) surface in the c(4x2) geometry. This system presents a unique opportunity to consider the complex interplay at work when a molecule with 3-fold symmetry binds to a surface with 4-fold symmetry. Our calculations find an upright structure for the PF3 molecules, in contrast to experimental claims. The phonon analysis reveals an intersting coupling between adsorbate modes, surface mods and bulk modes. We will present detailed calculational evidence, including phonon density of states and projected density of states to support the rich structural and vibrational behavior that this system affords. |
Tuesday, March 3, 2020 12:27PM - 12:39PM |
G58.00005: First-principles simulations of photocatalytic systems for hydrogen production Samuel Lemay, Gabriel Antonius Hydrogen offers a green alternative to fossil fuels, as it can be used in combination with fuel cells to propel an electric vehicle. In order to assist the design of photocatalytic systems for hydrogen production, we perform first-principles calculations of the electronic structure of several catalysts and attempt to predict their efficiency for hydrogen evolution reactions. One class of catalysts are coordination complexes composed of a metallic atom surrounded by organic ligands. In the present work, we focus on Co(bpy)2 and Co(bpym)2 where (bpy) is a bipyridine ligand and (bpym) is a bipyridine mimic. We rely on density functional theory (DFT) to compute the structural parameters of the molecules, their formation energy, and electronic energy levels. We aim to calculate the energy levels of the neutral, charged, and hydrogenated states of the molecules and compare it to cyclic voltammetry measurements. |
Tuesday, March 3, 2020 12:39PM - 12:51PM |
G58.00006: The Dirac equation and its implications for density functional theory-based calculations of materials containing heavy elements Daniel A Rehn, John M Wills, Ann E Mattsson Electronic structure calculations based on density functional theory (DFT) typically give quantitatively accurate predictions for ground-state properties of materials containing light elements. For materials containing heavy elements, relativistic effects play an increasingly important role and in principle, a formulation of DFT based on the Dirac equation is needed to properly incorporate relativistic effects. Working towards that goal, we have developed a code, called dirac-fp, that solves the Dirac-Kohn-Sham equations under the assumption of a vanishing orbital current. The dirac-fp code is based on the full potential linear muffin tin orbital (FP-LMTO) code RSPt, but solves the Dirac-Kohn-Sham equations throughout the entire computational cell. To assess the results of the Dirac-Kohn-Sham (Dirac) approach, we compare the ground state properties to the scalar relativistic (SR) and scalar relativistic+spin-orbit coupling (SR+SO) approaches for three different non-magnetic FCC materials: thorium, aluminum, and gold, in which relativistic effects should be strong, negligible, and intermediate, respectively. We find that only the Dirac approach is able to provide consistent results in the electronic structure and ground state properties across all three materials. |
Tuesday, March 3, 2020 12:51PM - 1:03PM |
G58.00007: Effect of functional -NH2 groups on sensitization of 3,6-diaminocarbazole towards Picric Acid Vishal Kumar, Soumitra Satapathi Due to the significance of explosive detection for homeland security and environmental protection, the research of new materials and methodologies for sensing electron-deficient explosive nitroaromatics is urgently imperative. In this paper we demonstrate an opto-chemical sensor for explosive detection by using a carbazole derivative, namely 3,6-diaminocarbazole (DAC) (Φf=49%), was synthesized through controlled nitration of the carbazole (Φf=42%) with fuming nitric acid. As a proof of concept, electron-deficient explosive molecule 2,4,6-trinitrophenol (TNP) is used as a model analyte to our sensor with LOD 3.7µM. In solution, PL signal from highly electron-rich DAC gets quenched upon addition of aliquots of TNP caused by photo-induced electron and resonance energy transfer i.e. quantified by Stern-Volmer constant (KSV= 4.1×104 M-1) which is higher than KSV=3.3×104 M-1,valuated for carbazole. The quenching mechanism was further established by time-resolved PL and steady state absorption spectroscopy which was found to be a mixture of static and dynamic in nature as lifetime of DAC (2.18 ns) is reduced to 1.24 ns for TNP. As a conclusion, results indicate that major response of this sensitivity enhancement to TNP originates from Föster Resonance Energy Transfer between DAC and TNP |
Tuesday, March 3, 2020 1:03PM - 1:15PM |
G58.00008: Charge Transport Properties of Biomolecules Abhishek Aggarwal, SAIENTAN BAG, Ravindra Venkatramani, Manish Jain, Prabal K Maiti Double-stranded DNA (dsDNA) and dsRNA hold great promises in molecular electronics. We characterize the charge transport properties of dsRNA for different sequences and compare them with similar sequences of dsDNA in two extreme charge transport regimes – incoherent charge hopping regime and coherent electron transport regime. We find that the relative conductance of A-form dsRNA and B-form dsDNA depends on the mechanism of charge transport. This is attributed to various structural differences in dsDNA and dsRNA. We also study the effect of stretching and propose a method to detect conformational changes using electrical measurements. Despite the twist-stretch coupling of dsRNA and dsDNA being different under external force, dsRNA shows similar structural polymorphism to dsDNA under different pulling protocols. Our atomistic MD simulations show that overstretching dsRNA along the 3’ ends (OS3) leads to the emergence of S-RNA whereas overstretching along the 5’ ends (OS5) leads to melting of dsRNA. Using the dsRNA morphology from MD simulations, we use a multiscale method involving ab initio DFT calculations and Kinetic Monte Carlo (KMC) simulations to estimate the conductance of dsRNA and find that the conformational changes drastically affect its conductance. |
Tuesday, March 3, 2020 1:15PM - 1:27PM |
G58.00009: Cyanide Bridged Platinum-Iron Complexes as Cisplatin Prodrug Systems: Design and Computational Study Ariela Kaspi-Kaneti, Srijana Bhandari, Barry Dunietz
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Tuesday, March 3, 2020 1:27PM - 1:39PM |
G58.00010: Detection of DNA nucleotides with Nanopores and Nanogaps from 2D Materials beyond Graphene: First Principle Studies Benjamin Tayo Sequencing the DNA at the resolution of individual DNA bases is an important problem whose solution could lead to cost-effective methods for sequencing the DNA, leading to revolutions in the field of genomics and personalized medicine. We present the results of computational studies on nano-bioelectronic devices combining the superb properties of 2D materials beyond graphene with DNA nucleotides. We anticipate our studies to shed useful insights that can help to address two major challenges in current sequencing technologies:1) strong coupling between 2D materials and nucleotides is expected to produce large signal-to-noise ratio compared to devices using graphene due to adsorption of nucleotides on graphene surface, or devices based on probing ionic currents, which often produce very low signal-to-noise ratio, 2) strong coupling between 2D materials and nucleotides is anticipated to produce large tunneling currents cable of accomplishing both spatial and temporal resolution at the single-base level. The performance of our proposed device for single-base sequencing will be evaluated by employing density functional theory and the nonequilibrium Green’s function method to investigate the transverse conductance properties of nucleotides inside the nanogap or nanopore. |
Tuesday, March 3, 2020 1:39PM - 1:51PM |
G58.00011: Electronic and optical properties of halide perovskite quantum dots: a DFT and TDDFT study. Athanasios Koliogiorgos, Tomas Polcar
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Tuesday, March 3, 2020 1:51PM - 2:03PM |
G58.00012: Efficient and Accurate Fully Relativistic Density Functional Treatment for Molecules and Periodic Solids Rundong Zhao, Victor Yu, Kimberly Zhang, Yunlong Xiao, Yong Zhang, Wenjian Liu, Volker Blum A fully relativistic density functional method (called quasi-four-component algorithm, Q4C) in combination with numeric atom-centered orbital (NAO) basis functions is presented. Q4C initially projects the atomic solution to (electron-only) positive-energy states and deals with only two components but restores the negative-energy component in a second step; it therefore retains the full precision of traditional four-component relativistic methods. While Q4C inherently reduces the dimension of the Hamiltonian matrix and correspondingly the computational demand in matrix diagonalization, the adoption of localized NAO basis functions further reduces the computational demand in real space operations, enabling us to explore large and complex systems containing heavy elements fully relativistically. Here, we report benchmarks for the properties of a series of common periodic materials and molecules. Additionally, the band structure of a much larger system, i.e. the 2D hybrid organic-inorganic perovskite (2D-HOIP) (4-FPEA)2PbI4 (containing 94 atoms per unit cell) is reported, showing the code's applicability to large systems. |
Tuesday, March 3, 2020 2:03PM - 2:15PM |
G58.00013: An Electronic Structure Approach to Understand Charge Transfer & Transport in Organic Semiconducting Materials Srijana Bhandari Effective design of optoelectronic devices requires understanding of the role of the molecular environment. However, widely used forms of DFT and TDDFT fail to accurately describe the frontier orbital gap and charge transfer states of such molecular systems in the condensed phase. Recently we implemented a novel approach combining screened RSH (SRSH) with polarized continuum model (PCM), where long range electrostatic interactions are consistently screened by a 1/e factor (e is the solid-state dielectric constant). Using this new approach, we achieved a highly efficient quantum chemical procedure to obtain condensed phase IP and EA based on single molecule calculations and the correct charge transfer energies of a complex system. |
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