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Article
Chemistry, Physical
Andreas Savin et al.
Summary: Sources of energy errors resulting from the replacement of the physical Coulomb interaction by its long-range erfc(mu r)/r approximation are explored in this study. The use of generalized cusp conditions to represent the wave function at small r is demonstrated to greatly improve the results and extend the range of mu for energies within chemical accuracy limits. The numerical results for a two-electron harmonium are presented and discussed.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Nery Villegas-Escobar et al.
Summary: The synthesis and characterization of novel aluminyl anion complexes have been extensively studied. By computationally analyzing the substituent effect on aluminyl anions, this research reveals that aluminyl systems with specific chelating centers (-C, -CN, -NC, and -N) are the most promising for hydrogen activation. Monosubstitution is also found to be preferred over disubstitution in aluminyl anions, suggesting that bidentate ligands may yield less reactive aluminyl anions compared to monodentate ones for H2 activation.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Sasha C. North et al.
Summary: In this study, CASSCF and MRCI+Q calculations were performed for LrF and LrO molecules, revealing 19 and 20 electronic states, respectively. Multiple dissociation channels were considered for both molecules, and various properties such as bond lengths, vibrational frequencies, anharmonicity constants, and excitation energies were calculated for the first time. Bond dissociation energies were also calculated using different levels of theory.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Ellena K. G. Black et al.
Summary: In this study, a significant shell pair is defined as one that generates at least one two-electron integral larger than a preset threshold in an electronic structure calculation. Similarly, a significant shell quartet is defined. Several methods are then explored to identify nonsignificant pairs and quartets in order to avoid them and improve computational efficiency. The widely used Cauchy-Schwarz bound is found to identify most nonsignificant quartets, while the Hölder bound is slightly more powerful for identifying nonsignificant pairs.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Juan I. Melo et al.
Summary: The FLOSIC method effectively removes the self-interaction error in the Perdew-Zunger framework by using localized Fermi-Lo''wdin orbitals. A detailed workflow for the implementation of the FLOSIC method in DFT calculations is provided, which takes advantage of the unitary invariant nature of the method. The algorithm's convergence characteristics are analyzed and applications for calculating NMR shielding constants and real-time time-dependent DFT simulations are presented.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Jose Aaron Rodriguez-Jimenez et al.
Summary: In this study, electronic structure calculations were performed to investigate the origin of spin-orbit couplings (SOCs) in open-shell molecules. Systems with di or polyradical character, such as trimethylene, were selected to analyze the changes in SOC constants during molecular distortions of ethylene and in the presence of intermolecular interactions in the O2-C2H4 system. The calculations utilized the restricted active space configuration interaction (RASCI) method to obtain nonrelativistic wave functions, along with a recent implementation for SOC calculations based on the spin-orbit mean field approximation. The results demonstrate the suitability of RASCI for calculating SOCs in open-shell systems and provide insights into the relationship between couplings and electronic states. Furthermore, a new definition of SOC constant for studying molecular aggregates is introduced.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Kie T. Workman et al.
Summary: The negative ion photoelectron spectra of 1,2-dicyanobenzene, 1,3-dicyanobenzene, and 1,4-dicyanobenzene radical anions were calculated using Frack-Condon (FC) factors. These calculations revealed the vibrational structure and electron affinities of the molecules in their different states. The results highlighted the potential stability of dicyano-polyaromatic hydrocarbons in the interstellar medium (ISM) and suggested the possibility of detecting them in future interstellar missions.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Olivia G. Haney et al.
Summary: Nonminimum carbonic acid clusters provide better excitation energies and oscillator strengths for observed ice-phase UV absorptions than traditional optimized minima. Quantum chemical analysis on carbonic acid monomers and dimers reveals that shifts to the dihedral angle of the internal heavy atoms produce UV electronic excitations close to 200 nm with observable oscillator strengths. The flexibility of the OCOO dihedral angle allows for lower-energy distortions that red-shift the observed spectra of carbonic acid ices away from the highest UV absorption feature at 139 nm.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Duy-Khoi Dang et al.
Summary: The heat-bath configuration interaction (HCI) method improves the computational efficiency for approaching the full CI limit. This study introduces computational improvements to the HCI algorithm, targeting speed, parallel efficiency, and memory requirements. The new implementation utilizes a hash function and MPI and OpenMP for parallelism, allowing for the study of a large active space and achieving high parallel efficiency. The accuracy of the new HCI implementation is benchmarked and applied to a challenging complex.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Du Luu et al.
Summary: Intra-molecular symmetry-adapted perturbation theory (ISAPT) is a method for calculating and analyzing the noncovalent interaction energy between two molecular fragments connected by a linker. The existing ISAPT algorithm has issues including artificial repulsive energy and large and mutually cancelling induction and exchange-induction terms. To address these issues, new partitioning algorithms are proposed to redistribute the electron density, leading to improved accuracy and convergence. This improved ISAPT partitioning approach has been applied successfully to various molecular systems.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Lukas Konecny et al.
Summary: This article presents two simple yet accurate two-component approaches for the calculation of X-ray absorption spectroscopy (XAS) using linear eigenvalue and damped response time dependent density functional theory (TDDFT) within an (extended) atomic mean-field exact two-component Hamiltonian framework. These approaches, namely amfX2C and eamfX2C, offer significant computational savings while reproducing all essential spectral features of the four-component (4c) references in excellent agreement.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Ernest Opoku et al.
Summary: A new generation of ab initio electron-propagator self-energy approximations without adjustable parameters is tested on a benchmark set of 55 vertical electron detachment energies. Comparisons with older self-energy approximations show that several new methods with diagonal self-energy approximation in the canonical Hartree-Fock orbital basis are more accurate and computationally efficient. These methods, along with their acronyms, mean absolute errors (in eV), and arithmetic bottlenecks expressed in terms of occupied (O) and virtual (V) orbitals, are the opposite-spin, non-Dyson, diagonal second-order method (os-nD-D2, 0.2, OV2), the approximately renormalized quasiparticle third-order method (Q3+, 0.15, O2V3), and the approximately renormalized, non-Dyson, linear, third-order method (nD-L3+, 0.1, OV4). The Brueckner doubles with triple field operators (BD-T1) nondiagonal electron-propagator method provides close agreement with coupled-cluster single, double, and perturbative triple replacement total energy differences, making it a potential alternative for obtaining standard data. The new methods with diagonal self-energy matrices serve as the foundation for estimating basis-set effects and predicting photoelectron spectra of nucleotides in DNA based on Dyson orbitals.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Montgomery Gray et al.
Summary: This study investigates the interaction energies and components in porous frameworks and finds that the van der Waals interaction is the main driving force for parallel-displaced pi-stacking, while electrostatics plays a minor role. The presence of a guest molecule limits the available slip-stacking configurations in COF-1.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Physical
Adem Halil Kulahlioglu et al.
Summary: The multistate formulation of the quantum Monte Carlo algebraic diagrammatic construction (ADC) method, QMCADC, is presented. QMCADC solves the Hermitian eigenvalue problem of the second-order ADC scheme for the polarization propagator stochastically by combining ADC schemes with projector quantum Monte Carlo. It allows for massively parallel distributed computing and exploits the sparsity of the effective ADC matrix, thereby relaxing memory and processing requirements of ADC methods significantly.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Yan Oueis et al.
Summary: Given a matrix representation of a local potential v(r) within a one-electron basis set of functions, it is possible to construct a well-defined local potential v(r) that has the form of an expansion in basis function products. Recent studies have shown that the reconstructed potentials from exchange-correlation potentials defined on the infinite-dimensional Hilbert space bear only qualitative resemblance to the original potentials. However, including low-lying virtual Kohn-Sham orbitals in the basis set improves the agreement between the reconstructed potentials and the original ones.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Avdhoot Datar et al.
Summary: We have investigated the Stark effect in small molecules in the soft x-ray region by examining field dependent x-ray absorption spectra. The effect is understood by considering the response of molecular orbitals, dipole moment, and geometry to an applied electric field. Consistent trends are observed between computed shifts in absorption energies and intensities with specific features of the molecular electronic structure. This study highlights the potential of x-ray Stark spectroscopy as a tool to study electronic structure and environmental perturbations at a submolecular scale.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Dennis R. Dombrowski et al.
Summary: A reformulation of the DFT/MRCI method is proposed, incorporating ab initio matrix element expressions to derive correction terms for an effective Hamiltonian. The derivation focuses on the problematic doubly excited 1 Delta g state and double excitations in general. Splitting the parameters for intra- and interorbital interactions is found to be necessary for a concise description of the underlying physics. Results for various states in different systems demonstrate the superiority of the presented formulation over previous effective Hamiltonians, while retaining all the benefits of previous DFT/MRCI Hamiltonians. Therefore, the presented formulation should be considered as the new standard for DFT/MRCI calculations.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Sarah Maier et al.
Summary: While accurate wave function theories are computationally intractable for large systems, density functional theory often fails to describe electronic changes in chemical processes. In this study, we propose an efficient Delta ML model that combines molecular fragmentation, systematic error cancellation, and machine learning to achieve coupled cluster accuracy for vertical ionization potentials by correcting for deficiencies in DFT.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Robbie J. Iuliucci et al.
Summary: The study finds that there are no practical advantages in using double-hybrid density functionals or MP2 to predict solid-state NMR chemical shifts and EFG tensor components for routine organic crystals. This is likely due to error cancellation benefiting hybrid functionals.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Pierre-Olivier Roy et al.
Journal of Physical Chemistry A
(2023)
Article
Chemistry, Physical
Mohammad Rahbar et al.
Summary: The lack of a procedure to determine equilibrium thermodynamic properties of a small system interacting with a bath is seen as a weakness in conventional statistical mechanics. Enclosing the small system in a large bath is one possible approach, but is limited by computational resources. In this study, a statistical thermodynamic model based on the grand canonical ensemble is proposed that accurately characterizes the properties of the system while avoiding the limitations of conventional methods.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Abdulrahman Aldossary et al.
Summary: Computational quantum chemistry becomes more than just numerical experiments when methods are tailored to explore chemical concepts. Energy decomposition analysis (EDA) is an important example, providing insights into the driving forces behind intermolecular interactions. The newly developed force decomposition analysis (FDA) complements EDA for understanding chemistry and offers more information for data analysis and force field training. By applying FDA, we analyze water interactions with sodium, chloride ions, and the water dimer, as well as the forces responsible for geometric changes of carbon dioxide adsorbed onto gold and silver anions.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Xindong Wang et al.
Summary: We utilize Self-Consistent Effective Hamiltonian Theory to derive a quadratic effective Hamiltonian for the Anderson impurity model, with a variational Fermionic many-body wave function. The exact solution to the chiral symmetry-breaking quadratic effective Hamiltonian yields the single Fermion excitation spectrum. Our theory is validated through numerical simulations, which show the presence of the correct Kondo resonance in the quasi-particle density of states.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Ruhee D'Cunha et al.
Summary: In this paper, we discuss potential issues associated with using hardware-efficient Ansa''tze in variational quantum simulations of electronic structure, including breaking Hamiltonian symmetries, obtaining nondifferentiable potential energy curves, and the difficulty of optimizing variational parameters. By comparing with unitary coupled cluster and full configuration interaction, and different strategies to encode Fermionic degrees of freedom to qubits, we explore the interplay between these limitations. Our analysis provides insights into the potential limitations of hardware-efficient Ansa''tze and identifies possible areas for improvement.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Review
Chemistry, Physical
Gaurav Harsha et al.
Summary: Wave function methods provide a reliable approach to study ground-state properties in quantum many-body systems. However, methods to study thermal properties have been lacking due to the difficulty of evaluating thermal properties involving the entire Hilbert space. In this review, we present a finite-temperature wave function formalism based on thermofield dynamics, which allows mapping the thermal density matrix to a pure state and generalizing ground-state wave function theories to finite temperatures.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Anna Kristina Schnack-Petersen et al.
Summary: We have implemented a damped response framework in the open-source program eT for calculating resonant inelastic X-ray scattering (RIXS) at the CCSD and CC2 levels of theory. The framework can be extended to higher excitation methods and multilevel approaches. We compared the results with the frozen-core core-valence separated approach in Q-Chem and experimental data. The performance of the CC2 method was evaluated and found to be inferior to CCSD for X-ray absorption spectra, but comparable for RIXS spectra.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
So Hirata et al.
Summary: This article presents a new method for studying helical polymers, which can calculate their energy, structure, and vibrational frequencies. It utilizes Gaussian spherical harmonics basis functions with frequency-dependent Dyson self-energy for infinite helical polymers. This method can handle incommensurable structures and can also predict the properties of infinitely catenated chains of nitrogen or oxygen.
JOURNAL OF PHYSICAL CHEMISTRY B
(2023)
Article
Chemistry, Physical
Maristella Alessio et al.
Summary: The robustness of the magnetic anisotropy and addressability of the spin states in nickelocene (NiCp2, Cp = cyclopentadienyl) make it an attractive spin sensor. However, the microscopic understanding of its magnetic anisotropy is lacking, especially when NiCp2 is used in quantum sensing devices on a surface. In this study, we use the spin-flip variant of EOM-CC method to investigate the magnetic behavior of NiCp2 and compare the results with SF-TD-DFT. Our calculations agree well with experimental data and reveal that the magnetic anisotropy in NiCp2 arises from a large spin-orbit coupling between the triplet ground state and the third singlet state. We also analyze the electronic structure of ring-substituted NiCp2 derivatives and NiCp2/MgO(001) adsorption complex using SF-TD-DFT, which provides insights into the retention of spin states and magnetic properties upon modification of the coordination environment and adsorption on a surface.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Physical
Amir Karton
Summary: The tight d functions have a significant chemical contribution to the total atomization energies in high-level coupled-cluster calculations, particularly at the CCSD and (T) levels. The study of 45 second-row species demonstrates the important influence of tight d functions on the 3d orbitals and total atomization energies of second-row atoms. Additionally, a simple natural bond orbital population analysis of the 3d orbitals provides a useful predictor for the impact of tight d functions on the post-CCSD(T) contribution to the total atomization energies.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Article
Chemistry, Physical
Nam Vu et al.
Summary: This study finds that the enantiomeric excess of chiral molecules can be altered using cavity quantum electrodynamics. By controlling the relative orientation of the molecules in the cavity, the preference for certain enantiomers can be enhanced or inverted without changing the chirality of the directing group.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Article
Chemistry, Physical
Renaldo T. Moura Jr et al.
Summary: LModeAGen is a new protocol based on chemical graph concepts for the automatic determination of a nonredundant, complete set of local vibrational modes. It provides a convenient way to analyze vibrational spectra of complex and large systems, offering new access to encoded electronic structure information.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Article
Chemistry, Physical
John P. Perdew et al.
Summary: The SCAN meta-GGA accurately describes equilibrium bonds with different correlations and symmetry breaking can correct underbinding. Advanced density functionals can reliably describe strong correlation. Breaking symmetry provides insights into strong correlation.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Article
Chemistry, Physical
Nathaniel L. Kitzmiller et al.
Summary: This study presents the most rigorous theoretical investigation to date on H2Sn=O and H2Pb=O, providing optimized energy results for oligomers and formaldehyde-like structures. These findings provide guidance for future detection of H2Sn=O or H2Pb=O.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Article
Chemistry, Physical
Cate S. Anstoeter et al.
Summary: The EFP approach is an effective method for including solvation effects in condensed phase properties and reactivity. This study examines the performance of the EFP method in describing microsolvation in electronically excited states. The results show minimal differences between QM/EFP and full quantum results when averaging over multiple configurations of microsolvated clusters, although individual configurations may have larger errors. Diffuse states have slightly larger errors, and QM/EFP may be less accurate in capturing state ordering changes. However, other properties such as photoelectron images and lifetimes are well described by the method.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
