Article
Chemistry, Physical
Gennady Chuev, Mohammadhasan Dinpajooh, Marat Valiev
Summary: Proper understanding of nanoparticle solvation processes requires accurate description of solvent molecular structure. Classical density functional theory (cDFT) can reproduce molecular dynamics (MD) simulation results at lower computational cost, allowing for the study of how solvent molecular features affect macroscopic system properties.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Tomoaki Yagi, Hirofumi Sato
Summary: A parameter-free bridge functional using a weighted density approximation (WDA) has been developed, which determines the free energy density in a self-consistent manner and allows for the use of any potential model. This method has been applied to calculate density distribution functions for inhomogeneous fluids interacting via different potentials under external fields.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Computer Science, Software Engineering
Rohan Sawhney, Dario Seyb, Wojciech Jarosz, Keenan Crane
Summary: This paper introduces a method for solving partial differential equations with spatially varying coefficients. By extending the walk on spheres algorithm from volumetric rendering to variable-coefficient problems, the exact solution for problems with detailed geometry and intricate coefficients can be obtained. This method does not require discretization of the problem and offers advantages such as unbiased Monte Carlo estimators and the ability to evaluate the solution at any point without solving a global system of equations.
ACM TRANSACTIONS ON GRAPHICS
(2022)
Article
Chemistry, Physical
Daniel Borgis, Sohvi Luukkonen, Luc Belloni, Guillaume Jeanmairet
Summary: This paper evaluates the ability of molecular density functional theory to predict the hydration free energies of molecular solutes and surrounding water structure efficiently and accurately. The theory is parameter-free and corrects typical approximations with a third-order bridge functional. Results show accurate descriptions of solvation free energy and structure for a variety of solutes, with room for improvement in H-bonding structure and hydration free energy of charged solutes.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Mathematics
Christopher N. Angstmann, Stuart-James M. Burney, Bruce I. Henry, Byron A. Jacobs, Zhuang Xu
Summary: We systematically introduce a class of functions that serve as fundamental solutions for autonomous linear integer-order and fractional-order delay differential equations. These functions, known as delay functions, are defined through power series or fractional power series that incorporate delays. In this study, we define delay exponential functions, delay trigonometric functions, and delay fractional Mittag-Leffler functions. We obtain Laplace transforms of the delay functions and demonstrate their usage in solving delay differential equations, extending and unifying previous work in this field.
Article
Mathematics, Applied
Manwai Yuen
Summary: In this article, the compressible Euler equations are studied using the classical functional techniques of Sideris and Makino-Ukai-Kawashima. The research shows that under certain conditions, the corresponding solution blows up on or before any finite time T > 0.
Article
Physics, Fluids & Plasmas
Takeru Yokota, Jun Haruyama, Osamu Sugino
Summary: This article introduces a functional renormalization group approach to classical liquids without the need for a repulsive reference like in previous methods. By using cavity distribution functions and selecting a specific path, errors are minimized, leading to accurate results in one-dimensional models when compared to integral equation methods.
Article
Biochemistry & Molecular Biology
Kati Finzel
Summary: This study introduces a new method for implementing density functional theory, which effectively handles interactions between atoms and reproduces bond-length contraction caused by multiple bonding in second-row homonuclear dimers.
Article
Mathematics
Hunter Johnston, Martin W. Lo, Daniele Mortari
Summary: In this paper, a method to solve for periodic orbits using the Theory of Functional Connections (TFC) is developed. By embedding the periodic constraint analytically into the TFC constrained expression, the system of differential equations governing the three-body problem is transformed into an unconstrained optimization problem, allowing for simpler numerical implementation with comparable accuracy and speed to traditional methods.
Article
Mathematics, Applied
Rafik Aguech, Wissem Jedidi, Samia Ilji
Summary: This paper investigates the two-dimensional fragmentation process that describes the evolution of an object with a rectangular shape. The focus is on a fragmentation process where a rectangle is broken according to a distribution dependent on its dimensions. Using renewal theory, the study provides the asymptotic behavior of the mean and variance of the distribution of the total number of sub-rectangles.
MATHEMATICAL METHODS IN THE APPLIED SCIENCES
(2022)
Article
Mathematics, Interdisciplinary Applications
Tahir Cosgun, Murat Sari
Summary: This study introduces a new algorithm called the reversed fixed point iteration method (RFPIM) to uncover the unstable equilibrium positions of a nonlinear system, which has been proven to have various advantages over conventional methods through mathematical analysis and numerical observations with illustrative examples.
CHAOS SOLITONS & FRACTALS
(2021)
Article
Mathematics, Applied
Sohrab Bazm, Pedro Lima, Somayeh Nemati
Summary: This paper investigates nonlinear functional Volterra-Urysohn integral equations, proving the existence and uniqueness of solutions using the Picard iterative method. Euler and trapezoidal discretization methods are utilized for numerical approximation, showing first order convergence for the Euler method and quadratic convergence for the trapezoidal method. A new Gronwall inequality is developed to prove the convergence of the trapezoidal method, with numerical examples demonstrating the functionality of the methods.
JOURNAL OF COMPUTATIONAL AND APPLIED MATHEMATICS
(2021)
Article
Materials Science, Multidisciplinary
Khaldoon Ghanem, Erik Koch
Summary: This paper explores a regularization method based on the repeated application of Tikhonov regularization under the discrepancy principle, for extracting information about the dynamical properties of physical systems from quantum Monte Carlo (QMC) simulations. The method can be readily implemented in any linear algebra package and gives results surprisingly close to the maximum entropy method (MaxEnt). We analyze the method in detail and demonstrate its connection to MaxEnt, as well as provide a straightforward method for estimating the noise level of QMC data.
Article
Chemistry, Physical
A. Coretti, T. Baird, R. Vuilleumier, S. Bonella
Summary: A new algorithm for efficient and fully time-reversible integration of orbital-free density functional theory (OFDFT) based molecular dynamics is presented. The algorithm adapts to the recently introduced Mass-Zero (MaZe) constrained dynamics and ensures adiabatic separation between nuclear and electronic degrees of freedom. The efficiency and accuracy of the algorithm are demonstrated through calculations of liquid sodium's static and dynamic properties.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
C. M. Horowitz, C. R. Proetto, J. M. Pitarke
Summary: This article investigates the behavior of the main components of the orbital-free density-functional theory on metal slabs, deriving explicit density functionals and conducting numerical calculations. The results show that a generally valid kinetic-energy density functional can be obtained for realistic many-particle fermionic systems.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
S. -C. Lin, G. Martius, M. Oettel
JOURNAL OF CHEMICAL PHYSICS
(2020)
Article
Materials Science, Multidisciplinary
Berthold Reisz, Eelco Empting, Matthias Zwadlo, Martin Hodas, Giuliano Duva, Valentina Belova, Clemens Zeiser, Jan Hagenlocher, Santanu Maiti, Alexander Hinderhofer, Alexander Gerlach, Martin Oettel, Frank Schreiber
Summary: Blended organic thin films, including pure and mixed films of CuPc and C60, were studied for their growth processes and morphologies. Experimental results showed the formation of a smooth wetting layer followed by rapid roughening in pure CuPc films, while C60 exhibited fast formation of distinct islands at an early growth stage.
PHYSICAL REVIEW MATERIALS
(2021)
Article
Chemistry, Physical
James F. Lutsko, Martin Oettel
Summary: The original derivation of power functional theory is reworked in detail to clarify and simplify the logic and make explicit the various functional dependencies. Issues with the original development are noted and a modification is suggested to avoid them. An alternative interpretation of the results is proposed, showing surprising similarities to classical density functional theory.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Chemistry, Physical
Young Choon Park, Ajith Perera, Rodney J. Bartlett
Summary: In this work, the time-independent and time-dependent EOM-CC oscillator strengths were implemented beyond the dipole approximation, including contributions beyond the quadrupole moment. This allows for the calculation of intensities for dipole inactive transitions, such as pre-edge transitions in metal K-edge spectra. The use of second-order oscillator strengths is demonstrated through TI-EOM-CCSD and TD-EOM-CCSD spectra of Ti4+ atoms.
JOURNAL OF CHEMICAL PHYSICS
(2021)
Article
Physics, Multidisciplinary
S. -C. Lin, M. Oettel, J. M. Haering, R. Haussmann, M. Fuchs
Summary: Direct correlation functions play a fundamental role in statistical mechanics, particularly in ordered phases. Through a demanding numerical approach, the DCF of a solid has been explicitly calculated for the first time, providing new insights into the elastic constants. It was found that the DCF of a solid significantly differs from its liquid counterpart at coexistence, mainly due to the influence of vacancies.
PHYSICAL REVIEW LETTERS
(2021)
Article
Chemistry, Physical
Saswati Ganguly, Gaurav Prakash Shrivastav, Shang-Chun Lin, Johannes Haering, Rudolf Haussmann, Gerhard Kahl, Martin Oettel, Matthias Fuchs
Summary: Different types of defects play a significant role in the mechanical response of complex crystals close to melting or at finite temperatures. Conventional elasticity theory fails to explain the motion of point defects in ordered crystalline structures. In this study, a first principles theoretical framework derived from microscopic equations of motion is used to investigate the elastic properties of a crystal with a high concentration of point defects. Predictions about the mechanical properties are validated through deformation experiments in molecular dynamics simulations.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Alexander Hinderhofer, Jan Hagenlocher, Alexander Gerlach, Joachim Krug, Martin Oettel, Frank Schreiber
Summary: Understanding the growth behavior of binary mixtures and its connection to the bulk phase behavior is a major challenge. In this study, we used X-ray reflectivity to determine the surface roughness and found systematic behavior depending on the intermixing, co-crystallization, or phase separation in the mixed films. Kinetic Monte Carlo simulations provided evidence that the lowered step edge barrier in the mixed films is induced by reduced in-plane crystallinity.
JOURNAL OF PHYSICAL CHEMISTRY C
(2022)
Article
Chemistry, Physical
Christian Beck, Marco Grimaldo, Hender Lopez, Stefano Da Vela, Benedikt Sohmen, Fajun Zhang, Martin Oettel, Jean-Louis Barrat, Felix Roosen-Runge, Frank Schreiber, Tilo Seydel
Summary: This study investigates the dependence of diffusion dynamics of macromolecules in biological systems on volume fraction using a simplified model system. The results suggest that a simple colloid picture accurately describes the short-time diffusion in binary mixtures.
JOURNAL OF PHYSICAL CHEMISTRY B
(2022)
Article
Chemistry, Physical
Frank Hirschmann, Hender Lopez, Felix Roosen-Runge, Tilo Seydel, Frank Schreiber, Martin Oettel
Summary: The researchers developed a coarse-grained, structure-based, low-resolution, 6-bead model for bovine serum albumin (BSA) and compared it with a 12-bead model for immunoglobulin G (IgG). They studied the effects of packing and flexibility on the behavior of these models in denser solutions. They also determined the effective sphere sizes of BSA.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Sahana Kale, Achim Lederer, Martin Oettel, Hans Joachim Schoepe
Summary: PMMA-PHSA particles have been used as a hard sphere model system since the 1980s. We investigate the fluid structure of fluorescent particles in three different solvents and compare them with analytical theory and computer simulations. The results show hard sphere behavior in decalin-TCE and charged sphere behavior in decalin-CHB and decalin-CHB-TBAB solvents, with reduced screening in the latter system compared to the bulk solvent.
Correction
Physics, Fluids & Plasmas
E. Empting, M. Klopotek, A. Hinderhofer, F. Schreiber, M. Oettel
Article
Physics, Fluids & Plasmas
E. Empting, N. Bader, M. Oettel
Summary: This study investigates the roughness and orientational order in thin films of anisotropic particles through kinetic Monte Carlo simulations. The results show that increasing anisotropy leads to a preferred orientation in the film, accompanied by non-equilibrium roughening effect and reordering in the film.
Article
Physics, Fluids & Plasmas
M. Maeritz, M. Oettel
Summary: A density functional based on fundamental measure theory is employed to study droplet states of lattice gas with next-neighbor attractions in three-dimensional finite systems. The findings show a sequence of droplets transitioning to cylinders and planar slabs, along with additional effects observed in the chemical potential curve upon temperature decrease. The analysis of the surface tension behavior reveals a dominant 1/Rs2 contribution with a hint of weak logarithmic contribution, which is smaller than the universal value predicted by field-theoretic methods.
Article
Physics, Fluids & Plasmas
M. Maeritz, M. Oettel
Summary: Researchers constructed a density functional for lattice gas or Ising model on square and cubic lattices based on lattice fundamental measure theory, mapping the model to a multicomponent model of hard particles and introducing polymer clusters to treat nearest-neighbor attractions. The resulting density functional for this nonadditive hard model showed significant improvement in planar interface tensions compared to standard mean-field functional and was close to simulation results in three dimensions.
Article
Physics, Fluids & Plasmas
E. Empting, M. Klopotek, A. Hinderhofer, F. Schreiber, M. Oettel
Summary: Thin-film growth is investigated in two types of lattice gas models with unequal interaction energy parameters for substrate and film particles. The models exhibit dynamic layering and flattening transitions, with the difference between particle-substrate and particle-particle interactions playing a central role for film morphology evolution at intermediate times.