A5025500898- Spectroscopy and Quantum Chemical Studies
- Machine Learning in Materials Science
- Quantum, superfluid, helium dynamics
- Computational Drug Discovery Methods
- Advanced Chemical Physics Studies
- Various Chemistry Research Topics
- Spectroscopy and Laser Applications
- Molecular spectroscopy and chirality
- NMR spectroscopy and applications
- Clay minerals and soil interactions
- Material Dynamics and Properties
- Advanced Thermodynamics and Statistical Mechanics
- Nanopore and Nanochannel Transport Studies
- Protein Structure and Dynamics
- Metabolomics and Mass Spectrometry Studies
- Electrostatics and Colloid Interactions
- Thermodynamic properties of mixtures
- Photosynthetic Processes and Mechanisms
- Muon and positron interactions and applications
- Innovative Microfluidic and Catalytic Techniques Innovation
- Pickering emulsions and particle stabilization
- Surface Modification and Superhydrophobicity
- Solid-state spectroscopy and crystallography
- Nonlinear Optical Materials Research
- Particle accelerators and beam dynamics
Queen's University Belfast
2021-2025
École Polytechnique Fédérale de Lausanne
2016-2020
University of Oxford
2012-2016
Nanyang Technological University
2014
Leatherhead Food Research
1960
Statistical learning methods show great promise in providing an accurate prediction of materials and molecular properties, while minimizing the need for computationally demanding electronic structure calculations. The accuracy transferability these models are increased significantly by encoding into procedure fundamental symmetries rotational permutational invariance scalar properties. However, tensorial properties requires that model respects appropriate geometric transformations, rather...
The electronic charge density plays a central role in determining the behavior of matter at atomic scale, but its computational evaluation requires demanding electronic-structure calculations. We introduce an atom-centered, symmetry-adapted framework to machine-learn valence based on small number reference model is highly transferable, meaning it can be trained data molecules and used predict larger compounds with low, linear-scaling cost. Applications are shown for various hydrocarbon...
The molecular dipole polarizability describes the tendency of a molecule to change its moment in response an applied electric field. This quantity governs key intra- and intermolecular interactions, such as induction dispersion; plays vital role determining spectroscopic signatures molecules; is essential ingredient polarizable force fields. Compared with other ground-state properties, accurate prediction considerably more difficult, this quite sensitive underlying electronic structure...
Ions induce changes in the H-bond network of water that extend by >20 nm, vary for H 2 O and D O, lead to surface tension anomalies.
We develop and present an improvement to the conventional technique for solving Hierarchical Equations of Motion (HEOM), which can reduce memory cost by up 75% while retaining same (or even better) convergence rate accuracy. This allows a full calculation population dynamics 24-site FMO trimer long time scales with very little effort, we first fully converged, exact results 7-site subsystem monomer, trimer. then show where our deviate from approximation Ishizaki Fleming [A. G. R. Fleming,...
The molecular dipole moment (μ) is a central quantity in chemistry. It essential predicting infrared and sum-frequency generation spectra as well induction long-range electrostatic interactions. Furthermore, it can be extracted directly-via the ground state electron density-from high-level quantum mechanical calculations, making an ideal target for machine learning (ML). In this work, we choose to represent with physically inspired ML model that captures two distinct physical effects: local...
The molecular structure of water is dynamic, with intermolecular hydrogen (H) bond interactions being modified by both electronic charge transfer and nuclear quantum effects (NQEs). Electronic NQEs potentially change under acidic or basic conditions, but such details have not been measured. In this work, we developed correlated vibrational spectroscopy, a symmetry-based method that separates interacting from noninteracting molecules in self- cross-correlation spectra, giving access to...
We combine classical and ring polymer molecular dynamics simulations with the jump model to provide a description of nuclear quantum effects (NQEs) on water reorientation hydrogen-bond in liquid H2O D2O. show that while net NQE is negligible D2O, it leads ∼13% acceleration compared description. Large angular jumps—exchanging partners—are dominant pathway (just as description); faster arise from increased rate constant. NQEs do not change amplitude distribution, no significant tunneling...
The impact of the vibrational coupling OH stretch mode on spectra differs significantly between IR and Raman water. Unified understanding couplings is not yet achieved. By using a different class spectroscopy, hyper-Raman (HR) together with machine-learning-assisted HR calculation, we examine water through comparison isotopically diluted H2O pure H2O. We found that isotopic dilution reduces bandwidths, but smaller than in parallel-polarized Raman. Machine learning indicate intermolecular...
Our current understanding of the structure and dynamics aqueous interfaces at molecular level has grown substantially due to continuous development surface-specific spectroscopies, such as vibrational sum-frequency generation (VSFG). As in other we must turn atomistic simulations extract all information encoded VSFG spectra. The high computational cost associated with existing methods means that they have limitations representing systems complex electronic or achieving statistical...
Isotope fractionation between different phases is a subtle but very important phenomenon that related to the quantum nature of light nuclei, and has consequences for geochemistry, hydrology, biology. Here we present joint experimental/theoretical investigation differential segregation hydrogen deuterium at liquid/vapor interface mixtures heavy water. We use both vibrational sum-frequency spectroscopy path integral molecular dynamics simulations quantitatively assess this phenomenon. The...
Mixtures of nano- and microscopic oil droplets in water have recently been rediscovered as miniature reaction vessels microfluidic environments are important constituents many environmental systems, food, personal care, medical products. The nanodroplet/water interface stabilized by surfactants determines the physicochemical properties droplets. Surfactants thought to stabilize nanodroplets forming densely packed monolayers that shield phase from water. This idea has inferred droplet...
The properties of molecules and materials containing light nuclei are affected by their quantum mechanical nature. Accurate modeling these nuclear effects requires computationally demanding path integral techniques. Considerable success has been achieved in reducing the cost such simulations using generalized Langevin dynamics to induce frequency-dependent fluctuations. Path equation methods, however, have this far limited study static, thermodynamic due large perturbation system's induced...
The surface tension of electrolyte solutions exhibits a minimum at millimolar concentrations and then rises with increasing concentration. This minimum, known as the Jones-Ray effect, has been hotly debated over past ∼80 years. If not considered an artifact, it is typically ascribed to phenomenological rare binding site for ions or ion pairs. Here, we propose alternative underlying mechanism, namely that hydrogen bond network water responds collective electrostatic field by its orientational...
We employ classical and ring polymer molecular dynamics simulations to study the effect of nuclear quantum fluctuations on structure water exchange aqueous solutions lithium fluoride ions. While we obtain reasonably good agreement with experimental data for by augmenting Coulombic interactions between ion molecules a standard Lennard-Jones ion-oxygen potential, same is not true fluoride, which find that potential softer repulsive wall gives much better agreement. A small degree...
Abstract While density functional theory (DFT) is often an accurate and efficient methodology for evaluating molecular properties such as energies multipole moments, this approach yields larger errors response the dipole polarizability ( α ), which describes tendency of a molecule to form induced moment in presence electric field. In work, we provide static tensors (and other total energy components, quadrupole etc.) computed using quantum chemical (QC) DFT methodologies all 7,211 molecules...
Abstract Accurately modelling nonlinear optical experiments such as second-harmonic scattering and hyper-Raman requires the hyperpolarizability $\boldsymbol{\beta}$, a dielectric response to an applied electric field. The tensor is computationally expensive quantity calculate, making it natural target for machine-learning methods. We test family of recently developed models water, trained on small clusters containing up 8 water molecules. These are able predict $\boldsymbol{\beta}$ larger...
Second-Harmonic Scatteringh (SHS) experiments provide a unique approach to probe non-centrosymmetric environments in aqueous media, from bulk solutions interfaces, living cells and tissue. A central assumption made analyzing SHS is that the each molecule scatters light according constant molecular hyperpolarizability tensor $\boldsymbol{\beta}^{(2)}$. Here, we investigate dependence of water on its environment internal geometric distortions, order test hypothesis We use quantum chemistry...
We introduce an atom-centered, symmetry-adapted framework to machine-learn the valence charge density based on a small number of reference calculations. The model is highly transferable, meaning it can be trained electronic-structure data molecules and used predict larger compounds with low, linear-scaling cost.
Vibrational spectroscopy is key in probing the interplay between structure and dynamics of aqueous systems. To map different regions experimental spectra to microscopic a system, it important combine them with first-principles atomistic simulations that incorporate quantum nature nuclei. Here we show large cost calculating vibrational systems can be dramatically reduced compared standard path integral methods by using approximate based on high-order integrals. Together state-of-the-art...
Long-range ion induced water-water correlations were recently observed in femtosecond elastic second harmonic scattering experiments of electrolyte solutions. To further the qualitative understanding these correlations, we derive an analytical expression that quantifies dipole-dipole a non-interacting gas dipoles. This model is logical extension Debye-H\"uckel theory can be used to qualitatively understand how combined electric field ions induces orientational distributions water molecules...