Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session G03: Electronic Structure in Open Science IIFocus
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Sponsoring Units: DCP Chair: Sina Mostafanejad, Virginia Tech Room: Room 126 |
Tuesday, March 7, 2023 11:30AM - 12:06PM |
G03.00001: MolSSI QCArchive - An Open-Source Platform for High-Throughput Generation, Analysis, and Sharing of Quantum Chemistry Data Invited Speaker: Benjamin Pritchard Large amounts of high-accuracy data is becoming more and more important in many areas of science, and chemistry is no exception. Whether the data is being used for machine learning, gathering of reference data for new methods, or screening large numbers of molecules for properties with general data mining approaches, generating the data is a foundational step in the process. |
Tuesday, March 7, 2023 12:06PM - 12:18PM |
G03.00002: Revisting Seminumerical Methods for Electronic Structure Calculations in the Age of Exascale Computing David B Williams-Young With the increasing reliance on the use of GPGPU accelerators in modern |
Tuesday, March 7, 2023 12:18PM - 12:54PM |
G03.00003: NWChemEx: Designing a computational chemistry app store for the exascale era (and beyond) Invited Speaker: Ryan M Richard With the advent of the exascale era, the NWChem team decided to rewrite the open-source NWChem package from the ground up. From conception, the resulting electronic structure package, NWChemEx, was envisoned as being a radical departure from the original NWChem. NWChemEx is written using object-oriented C++17 for performance, with all user-facing APIs mirrored in Python for user convenience. Internally, NWChemEx is entirely plugin-based, a design with a number of benefits including ease of refactoring, encapsulation, and interoperability. This presentation will primarily focus on the computer science behind NWChemEx's design, and how the design facilitates Open Science. In particular we describe how the design lays the foundations for a computational chemistry app store, and why such a design is imperative for performance at the exascale. |
Tuesday, March 7, 2023 12:54PM - 1:06PM |
G03.00004: Calculation of ionization potential of boron nitride clusters and quantum dots from iterative solution of the Dyson equation Arindam Chakraborty, Chandler D Martin The Dyson equation provides a systematic route for obtaining poles of the 1-particle Green’s function and calculating the ionization potential of chemical systems. The frequency-dependent self-energy operator in the Dyson equation contains all the necessary information about electron-correlation. However, even in its simplest form, the self-energy operator depends on 2particle-1hole (2p1h) and 1particle-2hole (1p2h) components and is computationally expensive to construct. In this work, we present the development of the stochastically stratified stochastic enumeration of molecular orbitals (SSE-MO) method which is designed to overcome this computational bottleneck. The SSE-MO method approximates the exact self-energy operator by a stochastic self-energy operator which is constructed from sampling the 2p1h and 1p2h space. The stratified sampling is implemented to systematically identify and include high-contributing terms from the 2ph1 and 1p2h space. The SSE-MO method was applied to investigate the ionization potential of a series of semiconductor boron nitride clusters and quantum dots and was used to construct the self-energy operator from a sample space of 109 2ph1 terms. A discussion on the effect of nanoparticle size, presence of surface ligands, and impact of defect sites on the ionization potential of quantum dots will be presented. |
Tuesday, March 7, 2023 1:06PM - 1:42PM |
G03.00005: Large-scale quantum atomistic electrochemistry simulations Invited Speaker: Chris-Kriton Skylaris We are developing software tools for atomistic electrochemical simulations under operational conditions. These new computational tools are not only capturing the essential chemistry and physics of devices such as batteries but can also give us the parameters needed for bridging atomistic with larger scale simulations. Our developments are within the ONETEP program [1] which is based on a linear-scaling reformulation of density functional theory (DFT) that allows atomistic simulations of orders of magnitude more atoms than conventional approaches, so that we can construct more realistic models. In this talk I will outline our developments so far which include methods for metallic systems, solvent and electrolyte models [2], and a grand-canonical approach which allows simulations at fixed voltage with respect to a computational reference electrode [3-4]. Finally I will present an application of these methods in recent simulations of the process of lithium metal deposition on anodes, which is a common mechanism for battery degradation [5]. |
Tuesday, March 7, 2023 1:42PM - 1:54PM |
G03.00006: High accuracy variational calculations of Pe and De states of small atoms using explicitly correlated Gaussian basis function Toreniyaz Shomenov, Sergiy Bubin In the framework of the Ritz variational method, we have implemented a new approach for calculating nonrelativistic energies and wave functions of few-electron atomic systems in states with dominant electron configurations containing two p-electrons or a single d-electron. In this approach we employed all-electron explicitly correlated Gaussian basis functions with prefactors in the form of bipolar harmonics. It allows to perform high accuracy calculations of both the ground and excited states, including the Rydberg series of states with n>10. The approach can also be extended to other quantum few-body systems such as small molecules, systems containing exotic particles, etc. We validated the new implementation by carrying out several benchmark calculations of Pe and D states of the boron and carbon atoms and obtained the most accurate non-relativistic energies of these states to date. The generated wave function can then be used to evaluate leading relativistic and QED corrections, further improving the accuracy of theoretical calculations of atomic spectra. |
Tuesday, March 7, 2023 1:54PM - 2:30PM |
G03.00007: Describing the electronic structure of molecules in strong magnetic fields Invited Speaker: Stella Stopkowicz When Coulomb- and magnetic forces compete, our “chemical intuition” about the electronic structure of atoms in molecules is challenged. For example, new bonding mechanisms arise where otherwise unbound systems like the H2 triplet become bound in a magnetic field perpendicular to the molecular axis.[1] Potential energy surfaces depend strongly on the orientation of the magnetic field and exhibit a plethora of level crossings and avoided crossings which has a strong influence on transition wavelengths and intensities in electronic spectra. |
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