Article
Chemistry, Physical
Fionn D. Malone, Ankit Mahajan, James S. Spencer, Joonho Lee
Summary: In this paper, we report the development of a Python-based AFQMC program called ipie, including timing benchmarks and new results on the isomerization of [Cu2O2]2+. We demonstrate the support for both CPUs and GPUs in ipie and show its interface with PySCF as well as a simple template for adding new estimators. Our benchmarks show that ipie is faster or similarly performing compared to other C++ codes on both CPUs and GPUs. Moreover, our results on [Cu2O2]2+ demonstrate the accuracy and efficiency of ipie in handling systems with moderate strong correlation and large-scale dynamic correlation.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2023)
Article
Biochemistry & Molecular Biology
Alexey G. Gerbst, Vadim B. Krylov, Nikolay E. Nifantiev
Summary: The study investigates the conformational behavior of galactofuranoside rings and suggests that changes in the orientation of a lactic acid residue at O-3 may induce conformational changes. These findings are important for further modeling of carbohydrate-protein interactions.
FRONTIERS IN MOLECULAR BIOSCIENCES
(2021)
Article
Quantum Science & Technology
William Kirby, Bryce Fuller, Charles Hadfield, Antonio Mezzacapo
Summary: This paper presents a method for encoding second-quantized fermionic systems in qubits. The encoding reduces the number of required qubits significantly when the number of fermions is much smaller than the number of modes. By incorporating this encoding into randomized simulation methods, it enables polylogarithmic simulation of fermionic systems with low dependence on the number of modes.
Article
Chemistry, Physical
Vladimir Palivec, Radek Pohl, Jakub Kaminsky, Hector Martinez-Seara
Summary: Determining the structure of saccharides in their native environment is crucial for understanding their function. In this study, we propose two cost-effective protocols for simulating sugar chemical shifts and recommend their use. These protocols not only help interpret experimental spectra, but can also independently predict structure.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)
Article
Chemistry, Physical
Yuriy Yu. Rusakov, Irina L. Rusakova
Summary: This paper introduces a new method for generating property-energy consistent (PEC) basis sets that can be applied to any arbitrary molecular property. The basis set generated by the PEC method is optimized for the specific molecular property of interest, providing the least possible total molecular energy. The main algorithm of the PEC approach involves Monte Carlo simulations to generate random exponents within a predetermined range.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Satya P. Joshi, Timo T. Pekkanen, Prasenjit Seal, Raimo S. Timonen, Arkke J. Eskola
Summary: The kinetics of the reaction between resonance-stabilized (CH3)(2)CCHCH2 radical and O-2 were investigated, showing different behaviors at low and high temperatures. At high temperatures, additional reaction channels appeared to open.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Yuriy Yu. Rusakov, Irina L. L. Rusakova
Summary: The basis sets used in quantum chemical calculations of P-31 NMR chemical shifts have a significant impact on their accuracy. Existing basis sets for phosphorus atom lack flexibility in important angular regions, leading to misassignments in P-31 NMR spectra. This study proposes new pecS-n (n = 1, 2) basis sets that demonstrate high accuracy and are useful in large-scale quantum chemical calculations of P-31 NMR chemical shifts.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Tommaso Giovannini, Henrik Koch
Summary: A novel energy-based localization procedure for molecular orbitals is presented, utilizing a multiscale framework and partitioning the system into active and inactive fragments. The method maximizes repulsion between fragments to obtain localized molecular orbitals, and has been applied to both conjugated and non-conjugated systems. Comparisons with reference values show the method's potential for reducing computational cost while expanding the application range of high-level electron correlation methods.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Nanoscience & Nanotechnology
Hamadou Hadidjatou, Olivier Holtomo, Ousmanou Motapon
Summary: This study investigates the effects of solvents on the structures and nuclear magnetic resonance spectroscopy of three pro-lithospermate molecules. The solvent effects on the geometrical parameters are found to be weak, and better results are obtained by using the B3LYP-D3BJ/6-31++G(d,p) method in DMSO for the calculation of chemical shifts.
Article
Chemistry, Physical
Wlodzimierz Makulski, Mateusz Godlewski
Summary: In this study, the properties of ethanol isotopic species in gas and liquid states were investigated in detail by nuclear magnetic resonance spectroscopy, including nuclear shielding constants, second virial coefficients, and spin-spin coupling constants. The changes in NMR parameters under different phases and isotopic compositions were measured, revealing the association processes that occur during condensation.
JOURNAL OF MOLECULAR STRUCTURE
(2022)
Article
Chemistry, Physical
Sophia Burger, Filippo Lipparini, Juergen Gauss, Stella Stopkowicz
Summary: This paper presents a method for calculating NMR shieldings using GIAOs and CD, and investigates the accuracy and applicability of this method in calculations involving up to 100 atoms and more than 1000 basis functions.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Jonathan H. Fetherolf, Fabijan Pavosevic, Zhen Tao, Sharon Hammes-Schiffer
Summary: Nuclear quantum effects, such as zero-point energy, play an important role in chemical and biological processes. The implementation of the nuclear-electronic orbital (NEO) framework allows for the quantum mechanical treatment of electrons and specific nuclei at the same level, inherently including such effects. The NEO-SOS'-OOMP2 method efficiently predicts proton affinities and relative energies of protonated water tetramer isomers, and its application to larger systems with multiple quantum protons is possible. Anharmonicity is critical for accurate relative energy calculations, and the NEO-SOS'-OOMP2 approach captures anharmonic zero-point energies in a computationally efficient manner, making it valuable for studying reaction paths and dynamics in chemical systems.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2022)
Article
Chemistry, Physical
Yuriy Yu. Rusakov, Irina L. Rusakova
Summary: This paper demonstrates the performance of the previously suggested property-energy consistent method on the calculation of chemical shifts. The results show that the proposed basis sets can accurately calculate the chemical shifts of hydrogen, carbon, nitrogen, and oxygen.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
James H. Thorpe, Josie L. Kilburn, David Feller, P. Bryan Changala, David H. Bross, Branko Ruscic, John F. Stanton
Summary: This study establishes empirical, highly accurate non-relativistic electronic total atomization energies and analyzes the performance of high-level ab initio quantum chemical calculations and the HEAT family of theoretical methods. The results show that the HEAT-345(Q) method benefits from fortuitous error cancellation and lays the foundation for extended HEAT variants with substantial improvements in accuracy.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Caspar Jonas Schattenberg, Morten Lehmann, Michael Buehl, Martin Kaupp
Summary: A variety of density functionals were evaluated for experimental 3d transition metal NMR shifts, with the recently implemented CDFT versions of two meta-GGAs showing the best performance. Global hybrids and local hybrids also performed well, while other functionals had deviations in the range of 5-6%.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2022)