arXiv subjects

Krishan Kanhaiya

Publications and source records attributed to Krishan Kanhaiya.

4 recordsLinked to original sources

arXiv2026

INTERFACE Force Field for Alumina with Validated Bulk Phases and a pH-Resolved Surface Model Database for Electrolyte and Organic Interfaces

Alumina and aluminum oxyhydroxides underpin chemical-engineering technologies from heterogeneous catalysis, corrosion protection, functional coatings, energy-storage devices, to biomedical components. Yet molecular models that predictively connect phase structure, pH-dependent surface chemistry, electrolyte organization, and adsorption across operating conditions remain limited. Here we introduce a unified INTERFACE Force Field (IFF) parameterization together with a curated, ready-to-use pH-resolved surface model database that provides the most accurate and transferable atomistic description of major alumina phases to date. The framework covers a-Al2O3, g-Al2O3, boehmite, diaspore, and gibbsite using a single, physically interpretable parameter set that is directly compatible with CHARMM, AMBER, OPLS-AA, CVFF, and PCFF. Across structural, thermodynamic, mechanical, and interfacial benchmarks, simulations reproduce experimental reference data with more than 95 percent accuracy, exceeding existing force fields and the reliability of current density-functional approaches. A key advance is the first transferable treatment of surface ionization and charge regulation across alumina phases over a broad range of pH values, enabling simulations of realistic solid electrolyte interfaces without phase-specific reparameterization. Quantitative reliability is demonstrated by reproducing trends in zeta potentials and pH-dependent adsorption of a corrosion inhibitor at alumina-water interfaces. Predicted adsorption free energies and surface contact times correlate with experiments across more than an order of magnitude. Relative to ML-DFT workflows, the speed 100 to 1000 times faster, reaching system sizes and time scales inaccessible to quantum methods. The results establish a predictive computational platform to design alumina-containing functional materials under realistic process conditions.

cond-mat.mtrl-sci↗

arXiv2025

Light-induced quantum friction of carbon nanotubes in water

Quantum friction describes the transfer of energy and momentum from electronically excited states in a material to a surrounding solvent. Here, we show that near-infrared (NIR) fluorescent single-walled carbon nanotubes (SWCNTs) exhibit quantum friction in water. The diffusion constants of functionalized SWCNTs in aqueous solution decrease linearly by around 50 % with increasing excitation power. In contrast, SWCNTs with quantum defects that localize excitons show no power-dependent diffusion. Chemical manipulation of exciton concentration by molecules that increase or decrease SWCNT fluorescence also modulate the diffusion constant by a factor of up to 2. Additionally, excitons increase the macroscopic viscosity of SWCNT solutions. Optical pump Terahertz (THz) probe spectroscopy reveals transient absorption features of water (37 /cm and above 80 /cm), indicating energy dissipation into translational modes of its hydrogen bond network. Molecular dynamics simulations further support a mechanism in which exciton-induced dipoles enhance frictional forces. These findings establish that excitons in SWCNTs induce quantum friction in water.

physics.optics↗

arXiv2024

Implementing Reactivity in Molecular Dynamics Simulations with Harmonic Force Fields

The simulation of chemical reactions and mechanical properties including failure from atoms to the micrometer scale remains a longstanding challenge in chemistry and materials science. Bottlenecks include computational feasibility, reliability, and cost. We introduce a method for reactive molecular dynamics simulations using a clean replacement of non-reactive classical harmonic bond potentials with reactive, energy-conserving Morse potentials, called the Reactive INTERFACE Force Field (IFF-R). IFF-R is compatible with force fields for organic and inorganic compounds such as IFF, CHARMM, PCFF, OPLS-AA, and AMBER. Bond dissociation is enabled by three interpretable Morse parameters per bond type and zero energy upon disconnect. Use cases for bond breaking in molecules, failure of polymers, carbon nanostructures, proteins, composite materials, and metals are shown. The simulation of bond forming reactions was included via template-based methods. IFF-R maintains the accuracy of the corresponding non-reactive force fields and is about 30 times faster than prior reactive simulation methods.

cond-mat.stat-mech↗

arXiv2020

ReaxFF reactive force field study of polymerization of polymer matrix in carbon nanotube-composite system

Human transport to Mars and deep space explorations demand the development of new materials with extraordinary high performance-to-mass ratios. Promising candidates to fulfill these requirements are ultrahigh strength lightweight (UHSL) materials, which consist of polymer matrices fortified by pristine carbon nanotubes (CNTs). Previous investigations have showed that with an increase in CNT diameter, its preferred configuration changes from a circular form to a flattened shape that can be obtained in high pressure or tension conditions. The ReaxFF reactive force field can reveal detailed chemical interactions at the atomistic scale. To enable ReaxFF simulations on CNT/polymer interfaces, we trained force field parameters to capture the proper structure of flattened carbon nanotubes (flCNTs), i.e. dumbbell-like shape CNTs, against available polymer consistent force field -- interface force field (PCFF-IFF) data which had good proximity to density functional theory (DFT) data. In this study we used accelerated ReaxFF molecular dynamics simulation using the optimized force field to study the polymerization of diglycidyl ether of bisphenol F (Bis F) and diethyltoluenediamine (DEDTA) molecules in vicinity of circular and flattened CNTs. Our results indicate that the flat regions of flCNT are more favorable spots for the polymers to settle compared to curved regions due to higher binding energies. Moreover, higher dimer generation around flCNT results in more effective coating of the CNT which leads to higher load transfer in compared to circular CNT. According to our results there is a high alignment between polymers and CNT surface which is due to strong pi-pi interactions of aromatic carbon rings in the polymers and CNTs. These ReaxFF simulations indicate the capability of this method to simultaneously observe the polymerization of monomers along with their interactions with CNTs.

physics.chem-ph↗