Chemical Physics
New submissions
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New submissions for Fri, 10 May 24
- [1] arXiv:2405.05338 [pdf, other]
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Title: Exploring the Influence of (n-1)d Subvalence Correlation and of Spin-Orbit Coupling on Chalcogen BondingComments: PCCP, submitted (Dr. Nisha Mehta is corresponding author)Subjects: Chemical Physics (physics.chem-ph)
This article presents a comprehensive computational investigation into chalcogen bonding interactions, focusing specifically on elucidating the role of subvalence (n$-$1)d and (n$-$1)sp correlation. The incorporation of inner-shell (n$-$1)d correlation leads to a decrease in interaction energies for chalcogen-bonded systems (at least those studied herein), contradicting the observations regarding halogen bonding documented by Kesharwani et al. in \textit{J. Phys. Chem. A}, \textbf{2018}, 122 (8), 2184-2197. The significance of (n$-$1)sp subvalence correlation appears to be lower by an order of magnitude. Notably, among the various components of interaction energies computed at the PNO-LCCSD(T) or DF-CCSD levels, we identify the PNO-LMP2 or DF-MP2 component of the (n$-$1)d correlation as predominant. Furthermore, we delve into the impact of second-order spin-orbit coupling (SOC2) on these interactions. Specifically, for the Te complexes, SOC2 effects rival (n$-$1)d correlation in importance; for the Se complexes, SOC2 is much less important. Generally, SOC2 stabilizes monomers more than dimers, resulting in reduced binding of the latter. Notably, at equilibrium and stretched geometries, SOC2 and (n$-$1)d destabilize the complex; however, at compressed geometries, they exhibit opposing effects, with (n$-$1)d becoming stabilizing.
- [2] arXiv:2405.05437 [pdf, other]
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Title: Measurement of Coherent Vibrational Dynamics with X-ray Transient Absorption Spectroscopy Simultaneously at the Carbon K- and Chlorine L$_{2,3}$- EdgesAuthors: Andrew D. Ross, Diptarka Hait, Valeriu Scutelnic, Daniel M. Neumark, Martin Head-Gordon, Stephen R. LeoneComments: ADR and DH contributed equally to this workSubjects: Chemical Physics (physics.chem-ph); Optics (physics.optics)
X-ray Transient Absorption Spectroscopy near the carbon K-edge (1s, $\sim$ 285 eV) and chlorine L$_{2,3}$ edges (2p, $\sim$ 200 eV) is used to study the nuclear dynamics of CCl$_4$ vibrationally activated by impulsive stimulated Raman scattering with a few-cycle 800 nm pump pulse. The totally symmetric stretching mode leads to a strong response in the inner-shell spectra, with the concerted elongation (contraction) in bond lengths leading to a red (blue) shift in the X-ray absorption energies associated with core-to-antibonding excitations. The relative slopes of the potential energy surfaces associated with the relevant core-excited states along the symmetric stretching mode are experimentally measured and compared to results from restricted open-shell Kohn-Sham calculations. A combination of experiment and theory indicates that the slope of the core-excited potential energy surface vs totally symmetric bond elongation is $-11.1 \pm 0.8$ eV/{\AA} for the Cl 2p$\to7a_1^*$ excitation, $-9.0\pm0.6$ eV/{\AA} for the Cl 2p$\to8t_2^*$ excitation and $-5.2\pm 0.4$ eV/{\AA} for the C 1s$\to8t_2^*$ excitation, to 95% confidence. The much larger slopes for the Cl 2p excitations compared to the C 1s state are attributed to greater contributions from Cl to the $7a_1^*$ or $8t_2^*$ antibonding orbitals to which the inner-shell electrons are being excited. No net displacement of the center of the vibrational wavefunction along the other vibrational modes is induced by the pump pulse, leading to absence of transient signal. The results highlight the ability of X-ray Transient Absorption Spectroscopy to reveal nuclear dynamics involving tiny ($<0.01$ {\AA}) atomic displacements and also provide direct measurement of forces on core-excited potential energy surfaces.
- [3] arXiv:2405.05440 [pdf, other]
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Title: Unbiasing Fermionic Auxiliary-Field Quantum Monte Carlo with Matrix Product State Trial WavefunctionsComments: 24 pages, 20 figuresSubjects: Chemical Physics (physics.chem-ph); Quantum Physics (quant-ph)
In this work, we report, for the first time, an implementation of fermionic auxiliary-field quantum Monte Carlo (AFQMC) using matrix product state (MPS) trial wavefunctions, dubbed MPS-AFQMC. Calculating overlaps between an MPS trial and arbitrary Slater determinants up to a multiplicative error, a crucial subroutine in MPS-AFQMC, is proven to be #P-hard. Nonetheless, we tested several promising heuristics in successfully improving fermionic phaseless AFQMC energies. We also proposed a way to evaluate local energy and force bias evaluations free of matrix-product operators. This allows for larger basis set calculations without significant overhead. We showcase the utility of our approach on one- and two-dimensional hydrogen lattices, even when the MPS trial itself struggles to obtain high accuracy. Our work offers a new set of tools that can solve currently challenging electronic structure problems with future improvements.
- [4] arXiv:2405.05559 [pdf, other]
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Title: Improved electrochemical performance of NASICON type Na$_{3}$V$_{2-x}$Co$_x$(PO$_{4}$)$_{3}$/C ($x=$ 0--0.15) cathode for high rate and stable sodium-ion batteriesComments: submittedSubjects: Chemical Physics (physics.chem-ph)
In recent years, the Na-ion SuperIonic CONductor (NASICON) based polyanionics are considered the pertinent cathode materials in sodium-ion batteries due to their 3D open framework, which can accommodate a wide range of Na content and can offer high ionic conductivity with great structural stability. However, owing to the inferior electronic conductivity, these materials suffer from unappealing rate capability and cyclic stability for practical applications. Therefore, in this work we investigate the effect of Co substitution at V site on the electrochemical performance and diffusion kinetics of Na$_{3}$V$_{2-x}$Co$_x$(PO$_{4}$)$_{3}$/C ($x=$ 0--0.15) cathodes. All the samples are characterized through Rietveld refinement of the x-ray diffraction patterns, Raman spectroscopy, transmission electron microscopy, etc. We demonstrate improved electrochemical performance for the $x=$ 0.05 electrode with reversible capacity of 105 mAh g$^{-1}$ at 0.1 C. Interestingly, the specific capacity of 80 mAh g$^{-1}$ is achieved at 10 C with retention of about 92\% after 500 cycles and 79.5\% after 1500 cycles and having nearly 100\% Coulombic efficiency. The extracted diffusion coefficient values through galvanostatic intermittent titration technique and cyclic voltammetry are found to be in the range of 10$^{-9}$--10$^{-11}$ cm$^{2}$ s$^{-1}$. The postmortem studies show the excellent structural and morphological stability after testing for 500 cycles at 10 C. Our study reveals the role of optimal dopant of Co$^{3+}$ ions at V site to improve the cyclic stability at high current rate.
- [5] arXiv:2405.05737 [pdf, other]
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Title: Neural Network Approach for Predicting Infrared Spectra from 3D Molecular StructureSubjects: Chemical Physics (physics.chem-ph)
Accurately predicting infrared (IR) spectra in computational chemistry using ab initio methods remains a challenge. Current approaches often rely on an empirical approach or on tedious anharmonic calculations, mainly adapted to semi-rigid molecules. This limitation motivates us to explore alternative methodologies. Previous studies explored machine-learning techniques for potential and dipolar surface generation, followed by IR spectra calculation using classical molecular dynamics. However, these methods are computationally expensive and require molecule-by-molecule processing. Our article introduces a new approach to improve IR spectra prediction accuracy within a significantly reduced computing time. We developed a machine learning (ML) model to directly predict IR spectra from three-dimensional (3D) molecular structures. The spectra predicted by our model significantly outperform those from density functional theory (DFT) calculations, even after scaling. In a test set of 200 molecules, our model achieves a Spectral Information Similarity Metric of 0.92, surpassing the value achieved by DFT scaled frequencies, which is 0.57. Additionally, our model considers anharmonic effects, offering a fast alternative to laborious anharmonic calculations. Moreover, our model can be used to predict various types of spectra (Ultraviolet or Nuclear Magnetic Resonance for example) as a function of molecular structure. All it needs is a database of 3D structures and their associated spectra.
- [6] arXiv:2405.05761 [pdf, other]
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Title: Spin parameter optimization for spin-polarized extended tight-binding methodsSubjects: Chemical Physics (physics.chem-ph)
We present an optimization strategy for atom-specific spin-polarization constants within the spin-polarized GFN2-xTB framework, aiming to enhance the accuracy of molecular simulations. We compare a sequential and global optimization of spin parameters for hydrogen, carbon, nitrogen, oxygen, and fluorine. Sensitivity analysis using Sobol indices guides the identification of the most influential parameters for a given reference dataset, allowing for a nuanced understanding of their impact on diverse molecular properties. In the case of the W4-11 dataset, substantial error reduction was achieved, demonstrating the potential of the optimization. Transferability of the optimized spin-polarization constants over different properties, however, is limited, as we demonstrate by applying the optimized parameters on a set of singlet-triplet gaps in carbenes. Further studies on ionization potentials and electron affinities highlight some inherent limitations of current extended tight-binding methods that can not be resolved by simple parameter optimization. We conclude that the significantly improved accuracy strongly encourages the present re-optimization of the spin-polarization constants, whereas the limited transferability motivates a property-specific optimization strategy.
- [7] arXiv:2405.05961 [pdf, other]
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Title: Towards comprehensive coverage of chemical space: Quantum mechanical properties of 836k constitutional and conformational closed shell neutral isomers consisting of HCNOFSiPSClBrAuthors: Danish Khan, Anouar Benali, Scott Y. H. Kim, Guido Falk von Rudorff, O. Anatole von LilienfeldSubjects: Chemical Physics (physics.chem-ph)
The Vector-QM24 (VQM24) dataset attempts to more comprehensively cover all possible neutral closed shell small organic and inorganic molecules and their conformers at state of the art level of theory. We have used density functional theory ($\omega$B97X-D3/cc-pVDZ) to optimize 577k conformational isomers corresponding to 258k constitutional isomers.Isomers included contain up to five heavy atoms (non-hydrogen) consisting of $p$-block elements C, N, O, F, Si, P, S, Cl, Br. Single point diffusion quantum Monte Carlo (DMC@PBE0(ccECP/cc-pVQZ)) energies are reported for the sub-set of the lowest conformers of 10,793 molecules with up to 4 heavy atoms.This dataset has been systematically generated by considering all combinatorially possible stoichiometries, and graphs (according to Lewis rules as implemented in the {\tt SURGE} package), along with all stable conformers identified by GFN2-xTB. Apart from graphs, geometries, rotational constants, and vibrational normal modes, VQM24 includes internal, atomization, electron-electron repulsion, exchange correlation, dispersion, vibrational frequency, Gibbs free, enthalpy, ZPV, molecular orbital energies; as well as entropy, and heat capacities. Electronic properties include multipole moments (dipole, quadrupole, octupole, hexadecapole), electrostatic potentials at nuclei (alchemical potential), Mulliken charges, and molecular wavefunctions. VQM24 represents a highly accurate and unbiased dataset of molecules, ideal for testing and training transferable, scalable, and generative ML models of real quantum systems.
Cross-lists for Fri, 10 May 24
- [8] arXiv:2405.05623 (cross-list from cond-mat.mtrl-sci) [pdf, ps, other]
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Title: Current progress in corrosion of multi principal element alloysAuthors: M. Ghorbani, Z. Li, Y. Qiu, P. Marcus, J.R. Scully, O. Gharbi, H. Luo, R.K. Gupta, Z.R. Zeng, H.L. Fraser, M.L. Taheri, N. BirbilisSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
Whilst multi-principal element alloys (MPEAs) remain a promising class of materials owing to several attractive mechanical properties, their corrosion performance is also unique. In this concise review, we present an emerging overview of some of the general features related to MPEA corrosion, following a decade of work in the field. This includes highlighting some of the key aspects related to the electrochemical phenomena in MPEA corrosion, and the relevant future works required for a holistic mechanistic understanding. In addition, a comprehensive database of the reported corrosion performance of MPEAs is presented, based on works reported to date. The database is assembled to also allow users to undertake machine learning or their own data analysis, with a parsed representation of alloy composition, test electrolyte, and corrosion related parameters.
Replacements for Fri, 10 May 24
- [9] arXiv:2304.02217 (replaced) [pdf, ps, other]
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Title: XPS analysis of molecular contamination and sp2 amorphous carbon on oxidized (100) diamondAuthors: Ricardo Vidrio, Daniel Vincent, Benjamin Bachman, Cesar Saucedo, Maryam Zahedian, Zihong Xu, Junyu Lai, Timothy A. Grotjohn, Shimon Kolkowitz, Jung-Hun Seo, Robert J. Hamers, Keith G. Ray, Zhenqiang Ma, Jennifer T. ChoySubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
- [10] arXiv:2404.09457 (replaced) [pdf, ps, other]
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Title: High-performance magnesium/sodium hybrid ion battery based on sodium vanadate oxide for reversible storage of Na+ and Mg2+Authors: Xiaoke Wang, Titi Li, Xixi Zhang, Yaxin Wang, Hongfei Li, Hai-Feng Li, Gang Zhao, Cuiping HanSubjects: Materials Science (cond-mat.mtrl-sci); Chemical Physics (physics.chem-ph)
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