Article
Chemistry, Physical
S. Benyoussef, R. Essajai, Y. El Amraoui, H. Ez-Zahraouy
Summary: This paper evaluates the physical properties of Fe3S4 material using Ab-initio calculations and Monte Carlo Simulations, revealing important parameters such as half-metallic behavior, critical exponents, and critical temperature. Additionally, the temperature-dependent magnetization for different crystal field values has been analyzed.
Article
Chemistry, Physical
Tina N. Mihm, William Z. Van Benschoten, James J. Shepherd
Summary: A new approach using low-cost calculations was developed to find a twist angle that matches the coupled cluster doubles energy in a finite unit cell. The method was shown to have comparable accuracy with exact methods beyond coupled cluster doubles theory. Additionally, for small system sizes, the same twist angle can be found by comparing energies directly, suggesting a potential route towards twist angle selection.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Materials Science, Multidisciplinary
Byungmin Kang, Junggi Yoon
Summary: Researchers have constructed a sign-problem-free variant of the SYK model, which retains all the essential properties of the original model while introducing an additional parameter M to control the number of terms in the Hamiltonian. They have found that this model exhibits non-Fermi-liquid physics beyond the conventional Fermi-liquid picture in the large-N limit.
Article
Chemistry, Physical
Jose Breton, Javier Hernandez-Rojas, Marta I. Hernandez, Jose Campos-Martinez, Tomas Gonzalez-Lezana
Summary: We propose a new analytical potential energy surface (PES) to describe the interaction between the trihydrogen cation and a helium atom in its electronic ground state. The PES is composed of two contributions: a polarization energy term due to the electric field generated by the molecular cation, and an exchange-repulsion and dispersion interactions represented by atom-bond potentials. The parameters of the PES are fitted from high-level ab-initio calculations and used for global optimization and quantum simulations to study the minimum energy configurations of small He clusters doped with H3+.
Article
Chemistry, Physical
Mikhail Petrik, Ilya Razumov, Yuri Gornostyrev, Inna Naschetnikova, Artemyi Popov
Summary: The ordering and decomposition processes in Ti-Al-X alloys were investigated using Monte Carlo simulations with first-principles parametrization. It was found that the stage of homogeneous ordering precedes the formation of ordered Ti3Al particles, and the duration of homogeneous ordering is sensitive to the annealing temperature and alloy composition.
Article
Materials Science, Multidisciplinary
S. Ait Jmal, M. Ait Tamerd, O. Mounkachi, J. P. Salvestrini, M. Balli
Summary: This study comprehensively examines the physical and magnetic features of orthorhombic perovskite-type RTiO3 using Density Functional Theory (DFT) and Monte Carlo simulations (MCs). The results reveal a metallic behavior and easy magnetization axis in (Ho, Er)TiO3 along the b and c directions, respectively. Compared to other perovskite oxides, (Ho, Er)TiO3 exhibits low magnetocrystalline anisotropy energy, indicating a weak rotating magnetocaloric effect. Exchange coupling interactions were calculated using the Ising model and utilized within the Heisenberg model for MCs, providing insights into the driving mechanisms underlying magnetocaloric and magnetic behaviors in (Ho, Er)TiO3.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Daria Ruth Galimberti, Joachim Sauer
Summary: A methodology is presented to calculate thermodynamic functions for adsorption at reduced computational cost, by computing vibrational partition functions and accounting for anharmonicities using reference structures. For methane, ethane, and propane adsorption in H-CHA zeolite, only two short trajectories are needed for convergence, with improved accuracy particularly in the entropy term. The computed thermodynamic functions correctly predict the trend in adsorption Gibbs free energy for methane, ethane, and propane.
JOURNAL OF CHEMICAL THEORY AND COMPUTATION
(2021)
Article
Nanoscience & Nanotechnology
Vrindaa Somjit, Bilge Yildiz
Summary: Identifying the structure of the Al2O3/Al interface is crucial for enhancing its performance in various applications. This study utilizes ab initio grand canonical Monte Carlo to explore the composition and configuration space of the interface, revealing its atomically sharp and layer-by-layer propagation nature. The insights obtained contribute to the design and engineering of Al2O3/Al-based corrosion coatings, controllable transistor technologies, and noise-free superconducting qubits.
ACS APPLIED MATERIALS & INTERFACES
(2022)
Article
Chemistry, Physical
Laura Weiler, Tina N. Mihm, James J. Shepherd
Summary: This article introduces a Gaussian process regression model for the transition structure factor in metal periodic coupled cluster singles and doubles calculations. The model is inspired by previous methods and uses a one-dimensional function to fit the structure factor and correct for finite size errors.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Juan J. J. Aucar, Alejandro F. F. Maldonado, Juan I. I. Melo
Summary: In this work, relativistic corrections to the electric field gradient (EFG) are presented, including spin-dependent corrections for the first time. The results show that these new corrections significantly improve the performance of the existing method and are in close agreement with calculations at the four-component Dirac-Hartree-Fock (4c-DHF) level. The accuracy of the EFG values obtained with this new method allows for the analysis of the electronic origin of relativistic effects using well-known nonrelativistic operators.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Hassan Ahmoum, Guojian Li, Yongjun Piao, Shiying Liu, Ralph Gebauer, Mourad Boughrara, Mohd Sukor Su'ait, Mohamed Kerouad, Qiang Wang
Summary: This study investigates the structural, electronic, and magnetic properties of Ni-doped ZnO nanoparticles synthesized using the sol-gel method. Results show that Ni-doped ZnO exhibits ferromagnetic and antiferromagnetic properties within certain Ni concentrations, making it a potential candidate as a diluted magnetic semiconductor.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Genetics & Heredity
Zhendong Liu, Yurong Yang, Dongyan Li, Xinrong Lv, Xi Chen, Qionghai Dai
Summary: The study introduces a new algorithm for RNA tertiary structure prediction, demonstrating high accuracy and completeness. By optimizing modeling results, the algorithm achieved excellent performance in experiments.
FRONTIERS IN GENETICS
(2022)
Article
Astronomy & Astrophysics
N. K. Timofeyuk, L. Moschini, M. Gomez-Ramos
Summary: This paper investigates the effects of a three-body force on nucleon transfer reactions in reactions with a loosely-bound projectile. The study finds that the three-body force can noticeably alter the angular distributions at forward angles and has consequences for spectroscopic factors' studies.
Article
Physics, Nuclear
A. Dehghan Niri, H. R. Moshfegh
Summary: This study calculates the number spectrum of nonequilibrium neutrinos resulting from the deviation of neutron star matter from beta equilibrium. Realistic descriptions of nuclear matter and the presence of free hyperons in the neutron star core are taken into account. The study finds that the addition of a three-body force interaction can significantly change the trend of the symmetry energy and thus the dominant flavor of the nonequilibrium neutrinos. The presence of hyperons also affects the value of the chemical potential gap noticeably.
Article
Physics, Multidisciplinary
G. Kadim, R. Masrour, A. Jabar, E. K. Hlil
Summary: This study investigated the magnetism of crystalline La0.75Sr0.25MnO3 perovskite using ab initio and Monte Carlo calculations, revealing its half-metallic ferromagnetic phase and potential for magnetic refrigeration applications. The results showed quantitative agreement with experimental transition temperatures and promising properties for room temperature magnetic refrigeration at moderate fields.
PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
(2021)
Article
Chemistry, Physical
Arjun Valiya Parambathu, Philip M. Singer, George J. Hirasaki, Walter G. Chapman, Dilipkumar Asthagiri
JOURNAL OF PHYSICAL CHEMISTRY B
(2020)
Article
Chemistry, Physical
Philip M. Singer, Arjun Valiya Parambathu, Xinglin Wang, Dilip Asthagiri, Walter G. Chapman, George J. Hirasaki, Marc Fleury
JOURNAL OF PHYSICAL CHEMISTRY B
(2020)
Biographical-Item
Chemistry, Physical
Henry S. Ashbaugh, Dilipkumar Asthagiri, Thomas L. Beck, Susan B. Rempe
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Article
Chemistry, Physical
Dilipkumar N. Asthagiri, Michael E. Paulaitis, Lawrence R. Pratt
Summary: The quasi-chemical theory QCT provides a practical way to calculate and conceptual framework for molecular hydration phenomena. It can be viewed from multiple perspectives, such as regularization of statistical thermodynamic problems, emphasis on solute neighborship characteristics, or inclusion of accurate electronic structure descriptions. The theory has been successfully applied to a wide range of solutes with different chemical complexities, providing guidance on necessary approximations and simplifications for calculations.
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Correction
Chemistry, Physical
Philip M. Singer, Arjun Valiya Parambathu, Xinglin Wang, Dilip Asthagiri, Walter G. Chapman, George J. Hirasaki, Marc Fleury, Kalina Ranguelova
JOURNAL OF PHYSICAL CHEMISTRY B
(2021)
Editorial Material
Chemistry, Physical
Arjun Valiya Parambathu, Thiago J. Pinheiro dos Santos, Walter G. Chapman, Dilipkumar N. Asthagiri
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Review
Chemistry, Multidisciplinary
Diego T. Gomez, Lawrence R. Pratt, Dilipkumar N. Asthagiri, Susan B. Rempe
Summary: This article reviews the quasi-chemical theory (QCT) used to evaluate the hydration free energies of ions, with a focus on anions such as halides. The study finds that QCT provides good agreement with experimental results and accurate numerical values for the inner-shell contribution. However, there may be issues when evaluating the outer-shell contribution for heavily hydrated, less effectively shielded ions. Sampling inner-shell structures from bulk solutions can improve the accuracy.
ACCOUNTS OF CHEMICAL RESEARCH
(2022)
Article
Chemistry, Physical
Rohan S. Adhikari, Arjun Valiya Parambathu, Walter G. Chapman, Dilipkumar N. Asthagiri
Summary: Calculating the hydration free energy of macromolecules has always been a challenge, but with the development of molecular quasi-chemical theory (QCT), it is now possible to calculate it within all-atom simulations. This study compares the results obtained using QCT with predictions from implicit solvent models and reveals the importance of cooperativity in hydration. The deviations between implicit and explicit solvent results highlight the limitations of additive models.
JOURNAL OF PHYSICAL CHEMISTRY B
(2022)
Article
Chemistry, Physical
Arjun Valiya Parambathu, Walter G. Chapman, George J. Hirasaki, Dilipkumar Asthagiri, Philip M. Singer
Summary: In this study, atomistic MD simulations were used to investigate the effects of nanoconfinement on the 1H NMR relaxation times T1 and T2 of heptane in kerogen. The results show that confinement plays an important role in reducing T1 by -3 orders of magnitude, in agreement with experimental measurements. For T2, confinement breaks spatial isotropy and gives rise to residual dipolar coupling, leading to a -5 orders of magnitude reduction compared to bulk heptane. Using the simulated T2, the surface relaxivity was calibrated to predict the pore-size distribution of organic nanopores in kerogen without additional experimental data.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Polymer Science
Winnie H. Shi, Rohan S. Adhikari, Dilipkumar N. Asthagiri, Amanda B. Marciel
Summary: We studied the influence of charge block length on the structure and behavior of polyampholyte chains using SAXS and molecular simulations. By synthesizing polyampholytes with different lengths of glutamic acid and lysine blocks, we found that longer blocks tend to induce phase separation. The addition of NaCl affected the phase behavior in a manner dependent on the charge block length. Our findings suggest the importance of electrostatic interactions and hydrogen bonding in phase separation and offer insights for intracellular condensates and material design.
Article
Chemistry, Physical
Chase E. Herman, Arjun Valiya Parambathu, Dilipkumar N. Asthagiri, Abraham M. Lenhoff
Summary: Electrostatic interactions in proteins are influenced not only by ionic charges but also by their chemical identities. This study investigates the varying strength of association of different monovalent molecular ions in protein-protein and protein-ligand interactions. A nonpolarizable model captures trends with cations, but not anions, while a continuum correction model considering electronic polarizability captures both trends at the cost of fidelity to the underlying ion-pair association energy landscape. A polarizable model proves crucial in capturing experimentally suggested trends for both cations and anions, altering the free energy landscape and configurational sampling.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Polymer Science
Winnie H. Shi, Rohan S. Adhikari, Dilipkumar N. Asthagiri, Amanda B. Marciel
Summary: In this study, the effect of charge block length on the conformation and phase behavior of polyampholyte chains was investigated using small-angle X-ray scattering (SAXS) and molecular simulations. The results showed that as the block size increased, the polyampholyte chains tended to phase separate. The addition of NaCl resulted in a salting-in effect in the phase separated polyampholytes, which was dependent on the charge block length. Fourier-transform infrared (FTIR) spectroscopy revealed the disruption of intramolecular hydrogen bonds upon the addition of NaCl, indicating the involvement of electrostatic interactions and hydrogen bonding in the phase behavior. SAXS spectra showed minimal dependence of charge block length on the radius of gyration (Rg) for soluble polyampholytes under no-added salt conditions, but local chain stiffening was found to be dependent on charge block length. With increasing NaCl, all polyampholytes expanded and behaved as neutral or swollen chains in good solvent conditions, consistent with electrostatic screening. Molecular simulations were in qualitative agreement with the experiments. The implications of this study for understanding intracellular condensates and material design were also highlighted.
Article
Chemistry, Physical
Arjun Valiya Parambathu, Walter G. Chapman, George J. Hirasaki, Dilipkumar Asthagiri, Philip M. Singer
Summary: This study investigates the effects of nanoconfinement on the 1H NMR relaxation times (T1 and T2) of heptane in kerogen using atomistic MD simulations. The results show that confinement plays an important role in reducing T1 by three orders of magnitude, in agreement with experimental measurements of heptane dissolved in kerogen. In addition, confinement breaks spatial isotropy and gives rise to residual dipolar coupling, leading to a five orders of magnitude reduction in T2. The simulated T2 is used to calibrate the surface relaxivity and predict the pore-size distribution of the organic nanopores in kerogen.
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
(2023)
Article
Chemistry, Physical
Thiago J. Pinheiro J. dos Santos, Arjun Valiya Parambathu, Carla C. Fraenza, Casey Walsh, Steve G. Greenbaum, Walter G. Chapman, Dilip Asthagiri, Philip M. Singer
Summary: In this study, the effects of temperature and concentration on r(1) of the Gd3+-aqua complex were investigated using molecular dynamics simulations and measurements. By expanding the autocorrelation function and determining the thermal activation energies, new insights into the molecular-scale physics of r(1) were revealed.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Philip M. Singer, Arjun Valiya Parambathu, Thiago J. Pinheiro dos Santos, Yunke Liu, Lawrence B. Alemany, George J. Hirasaki, Walter G. Chapman, Dilip Asthagiri
Summary: Atomistic molecular dynamics simulations were used to predict the T-1 relaxation of water caused by paramagnetic Gd3+ ions in solution at 25 degrees C. The simulations agreed closely with measurements within a certain frequency range, showing potential for predicting r(1) in chelated Gd3+ contrast agents for clinical MRI.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2021)