Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session B19: Van Der Waals Interactions in Molecules, Materials, and Complex Environments IIFocus Session Live
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Sponsoring Units: DCOMP Chair: Noa Marom, Carnegie Mellon Univ |
Monday, March 15, 2021 11:30AM - 12:06PM Live |
B19.00001: Polarizability and Image Potential States of Large Graphene Nanoflakes Invited Speaker: Kenneth Jordan Considerable experimental and theoretical work has been done on the image potential states of graphene. In a many-body treatment these states result from dispersion-type interaction between the excess electron and the electrons of graphene, but in a one-electron treatment these are attributed to the long-range -1/4z image potential. Non-valence correlation-bound (NVCB) anions of molecules and clusters are the finite system analog of image potential states. We have been addressing the evolution of the NVCB anion states of C6n2H6n polyaromatic hydrocarbons as well as of hypothetical C6n2 clusters (ignoring the effects of dangling bonds) as a function of n. Key to this effort is the development of a polarization model that includes both point-inducible dipoles and charge-flow polarization. We demonstrate that even for C6n2H6n species with over 10000 C atoms, the NVCB anion states a significantly different from the image potential states of graphene due to the electrostatic interactions with the periphery CH bonds. Inclusion charge-flow polarization is essential for the characterization of the NVCB anions of these nanoflake systems. |
Monday, March 15, 2021 12:06PM - 12:18PM Live |
B19.00002: Multipole Polarizabilites of Positronium and Its Interaction with Atoms and Molecules Jorge Charry Martínez, Matteo Barborini, Dmitry Fedorov, Alexandre Tkatchenko The positron, besides all its intriguing fundamental properties as the antimatter counterpart to the electron, may form metastable bound states with atomic/molecular systems before its annihilation [Rev. Mod. Phys. 82, 2557 (2010)]. One possible mechanism behind the formation of bound positron-electron states is the polarization of the electronic cloud towards the positron. Furthermore, the positron can take away an electron forming a positronium (Ps) atom, which then can have non-covalent interaction with regular matter. These interactions require an accurate description of electron-positron correlation effects. Here, we develop a highly-correlated quantum Monte-Carlo (QMC) approach by including electron-positron geminal orbitals and we apply it to study the polarization properties of Ps and its dispersion interaction with other atoms and molecules through the computation of polarizabilities and dispersion coefficients. The calculated multipole polarizabilites of Ps are compared to our analytical derivations based on the direct transition-matrix approach [Ann. Phys. 355, 153 (2015)]. The even-order polarizabilities are found vanishing suggesting that the dipole-dipole approximation should be enough to describe the interactions between Ps and matter. |
Monday, March 15, 2021 12:18PM - 12:30PM Live |
B19.00003: Impact of Van der Waals interactions on structural and nonlinear optical properties of azobenzene switches Carmelo Naim, Frédéric Castet, Eduard Matito
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Monday, March 15, 2021 12:30PM - 12:42PM Live |
B19.00004: Influence of Pore Size on the van der Waals Interaction in Two-Dimensional Molecules and Materials Yan Yang, Ka Un Lao, Robert Distasio Despite the importance of porous two-dimensional (2D) molecules and materials in advanced technological applications, the question of how the void space in these systems affects the van der Waals (vdW) scaling landscape has been largely unanswered. In this work [1], we present a series of analytical and numerical models which demonstrate that the mere presence of a pore leads to markedly different vdW scaling across non-asymptotic distances, with certain relative pore sizes resulting in effective power laws ranging from simple monotonic decay to the formation of minima, extended plateaus, and even maxima. These models are in remarkable agreement with first-principles approaches for the 2D building blocks of covalent organic frameworks (COFs), revealing that COF macrocycle dimers and periodic bilayers exhibit unique vdW scaling behavior which is quite distinct from their non-porous analogs. These findings extend across a wide range of distances relevant to the nanoscale, and represent an unexplored avenue towards governing the self-assembly of complex nanostructures from porous 2D molecules and materials. |
Monday, March 15, 2021 12:42PM - 12:54PM Live |
B19.00005: Phase behavior and electronic properties of a conducting ferrimagnetic metal-organic framework from first principles Alex Smith, Mike Ziebel, Sebastian Reyes-Lillo, Adam Jaffe, Jeffrey Long, Jeffrey Neaton Metal–organic frameworks (MOFs) are an emerging class of readily-tunable three-dimensional porous materials consisting of periodic arrays of metal cations connected by organic ligands. Most MOFs are insulating and nonmagnetic. CrCl2(pyrazine)2 [1] is a quasi-two-dimensional layered MOF with ferrimagnetic ordering below 55 K and a comparably large conductivity of 32 mS/cm at room temperature. Here, we perform first principles density functional theory calculations to understand the low temperature electronic, vibrational, and magnetic properties of CrCl2(pyrazine)2 at equilibrium and under compression, comparing with recent measurements of trends in structure and conductivity up to 15 GPa. |
Monday, March 15, 2021 12:54PM - 1:06PM Live |
B19.00006: Predicting CO adsorption on ZnO (10-10) and (11-20) surfaces using several van der Waals corrections to density functional theory Kyle Stoltz, Mario Borunda We study the adsorption of carbon monoxide (CO) onto the zinc oxide (ZnO) (10-10) and (11-20) surfaces. Our investigation utilizes Density Functional Theory (DFT) with the incorporation of van der Waals (vdW) interactions through a post DFT correction to the energy, and the addition of a nonlocal term to the correlation energy functional. We apply these methods to CO adsorption on locations around the pristine surfaces and defects such as a ZnO dimer defect and edge defects. Our results show that the inclusion of vdW interactions increases the calculated binding energy of CO to the ZnO surface, and that the vdW corrected binding energies exceed 1eV when the CO molecule settles within the ZnO dimer defect. |
Monday, March 15, 2021 1:06PM - 1:18PM Live |
B19.00007: Van der Waals density functional study of binding and separation of hydrocarbons in metal organic frameworks without open metal sites Timothy Quainoo, Sydney N Lavan, Zhenfei Liu Metal organic frameworks (MOFs) have received significant attention over the past years thanks to their promising features for binding, storage, and separation of guest molecules. MOFs without open metal sites are emerging as they are often less susceptible to poisoning compared to those with open metal sites. However, a complete understanding of the binding and separation mechanisms in such materials is still missing. In this work, we compare two classes of vanadium-based MOFs without open metal sites: MFM-300(VIII) and its oxidized iso-structural counterpart MFM-300(VIV), as well as MIL-47(VIII) and its oxidized counterpart MIL-47(VIV). We employ first-principles van der Waals density functional theory to compute the binding energies of a series of short-chain hydrocarbons, to understand their separation in these MOFs. Our study provides insight into the host-guest binding interactions, in particular the role played by the bridging -OH group in such materials. Our results successfully explain existing experiments and provide guidance for future experiments. |
Monday, March 15, 2021 1:18PM - 1:30PM Live |
B19.00008: Toward a General Non-Local Polarizability Density Functional for van der Waals Dispersion Interactions Szabolcs Góger, Péter Szabó, Dmitry Fedorov, Alexandre Tkatchenko Density-functional theory (DFT), while being a workhorse for electronic-structure calculations, struggles with describing van der Waals (vdW) dispersion interactions stemming from long-range electron correlations. Determining the correlation energy using the adiabatic connection fluctuation-dissipation theorem via a non-local polarizability density gives a general framework to tackle this problem [1], but a robust general formalism is yet to be found. Here, we present a unified formula for the non-local polarizability density based on the second-order perturbation theory expression for the polarizability. We analyze this function for the quantum harmonic oscillator and particle in a box, as two elementary model systems, and identify efficient numerical approximations. The electromagnetic coupling of two harmonic oscillators, treated non locally, is also considered. Our model studies along with prior work on semi-local polarizability functionals [2] pave the way toward developing a unified non-local polarizability functional for molecules and materials. |
Monday, March 15, 2021 1:30PM - 1:42PM Live |
B19.00009: van der Waals Interactions in Confined Spaces: Surprises Beyond the Random-Phase Approximation Martin Stoehr, Mainak Sadhukhan, Yasmine S. Al-Hamdani, Jan Hermann, Alexandre Tkatchenko The confinement of molecules is ubiquitous in realistic systems relevant to sensing, catalysis, energy materials or biophysics. The accurate description of such systems thus requires a deep understanding of intermolecular interactions under confinement. van der Waals (vdW) dispersion thereby represents a crucial part. vdW forces arise from Coulomb-coupled quantum-mechanical fluctuations in the electron density. However, the treatment of practically-relevant systems typically relies on the interatomic dipole limit or random-phase approximation (RPA), thus failing to capture the full complexity of vdW dispersion. We here present a consistent methodology to incorporate so-called dipole-correlated Coulomb singles (DCS) into an efficient many-body treatment of vdW forces through a perturbation expansion over the dipole-coupled state of the Many-Body Dispersion (MBD) model. DCS include so-far neglected beyond-dipolar correlation and dispersion-polarization terms beyond the RPA. Combining hybrid density-functional approximations with MBD+DCS yields high-accuracy binding energies for supramolecular complexes at low computational costs. In more complex environments, DCS can alter long-range interactions even qualitatively, which may allow to explain several puzzling experimental findings. |
Monday, March 15, 2021 1:42PM - 1:54PM Live |
B19.00010: Benchmark of DFT Functionals for the Interlayer Binding Energy of Bulk CrI3: A fixed-node quantum Monte Carlo study Tom Ichibha, Jaron Krogel, Fernando A Reboredo Significant attention has been focused on CrI3 since long range magnetic ordering in two-dimensional materials was first discovered in a-few-layered system. Theoretically, CrI3 has been studied mainly using density functional theory (DFT). However, it is still under debate which functional is the most accurate. Therefore, we benchmarked several DFT functionals targeting the interlayer binding energy of bulk CrI3. In absence of experimental data, we obtained reference values using the fixed-node quantum Monte Carlo (FNDMC), which is one of the most accurate ab initio methods for periodic systems. Comparisons of the interlayer binding energy and distance obtained with optB88-vdW, optB86b-vdW and other functionals with predicted values obtained with FNDMC will be presented. |
Monday, March 15, 2021 1:54PM - 2:30PM Live |
B19.00011: The measurement of van der Waals forces between two-dimensional materials and multilayer stacks in air and water Invited Speaker: Pavlo Gordiichuk Two-dimensional materials have a prime interest for applications in materials, chemistry, and biology, as possessing unique one atom thickness with extended lateral dimensions. Since many applications rely on interfacial stacking of 2D materials, understanding interactions between 2D sheets and in their multilayer stacks is of paramount importance. Our experimental strategy enables rapid and high-throughput experimental determination of forces between 2D materials both in air and in liquids using atomic force spectroscopy. We found that measured scaling of the van der Waals force as a function of separation distance substantially differs from theoretical predictions and depends on the number of layers. Conducted experiments in deionized water showed repulsive forces between two hydrophobic surfaces, which differ at higher ionic strength. Our experiments provide a new experimental strategy and much needed knowledge for the further development of van der Waals methodologies. |
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