Professor David Faux
About
Biography
David obtained a First Class Honours degree in Physics from Nottingham University, UK, a MSc in Physics and Technology of Nuclear Reactors from Birmingham University, UK and a PhD from Birmingham University, UK, in 1986. He then spent 2 years at North Carolina State University, Raleigh, NC, USA supported by a NATO Fellowship. He was appointed as a Lecturer at the University of Surrey in 1988 and promoted to Professor in 2022.
David is a member of the Soft Matter, Biomaterials and Medical Physics group of the Physics Department where he works as a theorist and computational modeller studying nano-porous materials of environmental interest. Simulation techniques include molecular dynamics and Monte Carlo. His theoretical work has been instrumental for the interpretation of fast-field-cycling NMR data on porous material such as cement-based material, clays and plaster, hydrogels and biomaterials.
University roles and responsibilities
- Deputy Chair, University Ethics Committee
ResearchResearch interests
David is a theoretical/computational condensed matter physicist with current research interests focusing on molecular dynamics, Monte Carlo and Lattice-Boltzmann techniques. Current work focuses on the behaviour of fluids (especially water) in porous media. This includes the nanoscale exploration of hydrated cement-based materials with the aim of improving the longevity and lowering the carbon footprint of cement-based materials.
David has made some important advances in the interpretation of frequency-dependent field-cycling NMR experimentation on a range of porous material, particle suspensions and pastes. He has produced a new model, the 3-tau model, capable of maximising the nanoscale fluid dynamical information that can be extracted from fits to FFC-NMR dispersion curves.
David's previous research interests focused chiefly on the modelling of stress/strain and piezoelectric fields in semiconductor quantum wires and dots. Numerical procedures, Green's functions, Fourier methods and atomistic simulations were used to determine the stress/strain fields which are of paramount importance in the determination of novel semiconductor device properties.
Research collaborations
Recent research collaborations have involved the consortium of universities and commercial organisations in the UK and Europe interested in the behaviour of cement materials. David is Surrey CI in a new EU Marie Curie grant award with collaborators at Alma Mater Studiorum - Universita di Bologna, Technische Universitaet Wien, Heidelbergcement AG and EPFL in Switzerland. Collaboration with the National Forestry commission for wood studies continues. David also collaborates with the King Abdulaziz University in Jeddah, Saudi Arabia, on a graphene project.
Research interests
David is a theoretical/computational condensed matter physicist with current research interests focusing on molecular dynamics, Monte Carlo and Lattice-Boltzmann techniques. Current work focuses on the behaviour of fluids (especially water) in porous media. This includes the nanoscale exploration of hydrated cement-based materials with the aim of improving the longevity and lowering the carbon footprint of cement-based materials.
David has made some important advances in the interpretation of frequency-dependent field-cycling NMR experimentation on a range of porous material, particle suspensions and pastes. He has produced a new model, the 3-tau model, capable of maximising the nanoscale fluid dynamical information that can be extracted from fits to FFC-NMR dispersion curves.
David's previous research interests focused chiefly on the modelling of stress/strain and piezoelectric fields in semiconductor quantum wires and dots. Numerical procedures, Green's functions, Fourier methods and atomistic simulations were used to determine the stress/strain fields which are of paramount importance in the determination of novel semiconductor device properties.
Research collaborations
Recent research collaborations have involved the consortium of universities and commercial organisations in the UK and Europe interested in the behaviour of cement materials. David is Surrey CI in a new EU Marie Curie grant award with collaborators at Alma Mater Studiorum - Universita di Bologna, Technische Universitaet Wien, Heidelbergcement AG and EPFL in Switzerland. Collaboration with the National Forestry commission for wood studies continues. David also collaborates with the King Abdulaziz University in Jeddah, Saudi Arabia, on a graphene project.
Teaching
I teach on the following modules:
- PHY1035 Scientific Investigation Skills (Year 1)
- PHY2069 Quantum Physics (Year 2)
- PHYM044 Non-ionising Radiation (MSc Medical Physics)
- as well as contributing to Final Year Projects and MSc Dissertation modules.
Publications
Highlights
Faux DA, Pearson GS Green's tensors for anisotropic elasticity: Application to quantum dots PHYS REV B 62 (8): R4798-R4801 AUG 15 2000
Pearson GS, Faux DA Analytical solutions for strain in pyramidal quantum dots J APPL PHYS 88 (2): 730-736 JUL 15 2000
Faux DA Molecular dynamics studies of hydrated zeolite 4A J PHYS CHEM B 103 (37): 7803-7808 SEP 16 1999
Andreev AD, Downes JR, Faux DA, et al. Strain distributions in quantum dots of arbitrary shape J APPL PHYS 86 (1): 297-305 JUL 1 1999
Faux D A, Cachia S-H P P, McDonald P J, Howlett N C, Bhatt J S and Churakov S V Model for the Diffusion of Water in Porous Silicate Materials Phys. Rev. E., 91, 032311 (2015)
Etzold M A, McDonald P J, Routh A F and Faux D A Kinetic Monte Carlo Model for 2D growth in 3D: competitive space filling by growing sheets Phys. Rev. E., 92, 042106 (2015) DOI: 10.1103/PhysRevE.92.042106
Faux D A, Howlett N C and McDonald P J Nuclear magnetic resonance relaxation due to the translational diffusion of fluid confined to quasi-two-dimensional pores Phys. Rev. E., 95, 033116 (2017) DOI: 10.1103/PhysRevE.95.033116
Faux D A and McDonald P J Explicit calculation of nuclear magnetic resonance relaxation rates in small pores to elucidate molecular scale fluid dynamics Phys. Rev. E., 95, 033117 (2017) DOI: 10.1103/PhysRevE.95.033117
Faux D A and McDonald P J A model for the interpretation of nuclear magnetic resonance spin-lattice dispersion measurements on mortar, plaster paste, synthetic clay and oil-bearing shale Microporous and Mesoporous Materials 269, 39-42 (2018) DOI: 10.1016/j.micromeso.2017.09.002
Faux D A and McDonald P J Nuclear-magnetic-resonance relaxation rates for fluid confined to closed, channel or planar pores Phys. Rev. E, 96, 063110 (2018) DOI: 10.1103/PhysRevE.98.063110
Faux D A and Godolphin J Manual timing in physics experiments: error and uncertainty Am. J. Phys., 87, 110 (2019) DOI: 10.1119/1.5085437
Faux D A, Kogon R, Bortolotti V and McDonald P J Advances in the interpretation of frequency-dependent nuclear-magnetic resonance measurements from porous material Molecules, 24 (20) 3688 (2019) DOI: 10.3390/molecules24203688
Faux D A, Shah M and Knapp C Games of Life Am. J. Phys., 88 (5), 1-17 (2020) DOI: doi.org/10.1119/10.0000666
McDonald P J, Istok O, Janota M, Gajewicz-Jaromin A M and Faux D A Sorption, anomalous water transport and dynamic porosity in cement paste: a spatially localised 1H NMR relaxation study and a proposed mechanism Cement and Concrete Research, 133, 106045 (2020).
McDonald P J, Borg M and Faux D A Mesoscale modelling of dynamic porosity in cement hydrate gel during water sorption cycle: a lattice Boltzmann study Cement and Concrete Research, 146, 106475 (2021) DOI: https://doi.org/10.1016/j.cemconres.2021.106475
Faux D A and Godolphin J The floating-point: tales of the unexpected Am. J. Phys., 89, DOI: https://doi.org/10.1119/10.0003915
Faux D A and Godolphin J The floating-point: rounding error in timing devices Am. J. Phys., 89, 8, (2021) DOI: https://doi.org/10.1119/10.0003919
A model linking the molecular-scale dynamics of fluids confined to nano-pores to nuclear magnetic
resonance (NMR) relaxation rates is proposed. The model is used to re-analyse fast field-cycling spinlattice
relaxation rate measurements for the separate water and oil dispersions from an oil-bearing shale
[Korb et al., J. Phys. Chem. C, 118, 199 (2014)]. The model assumes that pore fluid can be characterized by
three time constants: the surface and bulk diffusion correlation times and a surface desorption time
constant. Results are shown to yield meaningful and consistent intra-pore dynamical time constants,
insight into diffusion mechanisms and pore morphology. The shale is found to be oil-wetting and the
water dispersion is found to be due to the interaction of aqueous Mn2+ ions with bulk water spins. Clay,
mortar and plaster paste dispersions measurements have also been successfully re-analysed and a
summary of the results is presented. The results demonstrate the wide applicability of the model which
advances NMR dispersion experimentation as a powerful tool for measuring nano-porous fluid
properties.
Nuclear-magnetic-resonance (NMR) spin-lattice (T1^−1) and spin-spin (T2^−1) relaxation rate measurements can
act as effective nondestructive probes of the nanoscale dynamics of 1H spins in porous media. In particular, fast-field-cycling T1^−1 dispersion measurements contain information on the dynamics of diffusing spins over time scales spanning many orders of magnitude. Previously published experimental T1−1 dispersions from a plaster paste, synthetic saponite, mortar, and oil-bearing shale are reanalyzed using a model and associated theory which describe the relaxation rate contributions due to the interaction between spin ensembles in quasi-two-dimensional pores. Application of the model yields physically meaningful diffusion correlation times for all systems. In particular, the surface diffusion correlation time and the surface desorption time take similar values for each system, suggesting that surface mobility and desorption are linked processes. The bulk fluid diffusion correlation time is found to be two to five times the value for the pure liquid at room temperature for each system. Reanalysis of the oil-bearing shale yields diffusion time constants for both the oil andwater constituents. The shale is found to be oil wetting and the water (T1^−1) dispersion is found to be associated with aqueous Mn2+ paramagnetic impurities in the bulk water. These results escalate the NMR (T1^−1) dispersion measurement technique as the primary probe of molecular-scale dynamics in porous media yielding diffusion parameters and a wealth of information on pore morphology.
Nuclear-magnetic-resonance (NMR) relaxation experimentation is an effective technique for nondestructively probing the dynamics of proton-bearing fluids in porous media. The frequency-dependent relaxation rate T1^-1 can yield a wealth of information on the fluid dynamics within the pore provided data can be fit to a suitable spin diffusion model. A spin diffusion model yields the dipolar correlation function G(t ) describing the relative translational motion of pairs of 1H spins which then can be Fourier transformed to yield T1^-1. G(t ) for spins confined to a quasi-two-dimensional (Q2D) pore of thickness h is determined using theoretical and Monte Carlo techniques. G(t ) shows a transition from three- to two-dimensional motion with the transition time proportional to h2. T1^-1 is found to be independent of frequency over the range 0.01–100 MHz provided h 5 nm and increases with decreasing frequency and decreasing h for pores of thickness h < 3 nm.T1^-1 increases linearly with the bulk water diffusion correlation time τb allowing a simple and direct estimate of the bulk water diffusion coefficient from the high-frequency limit of T1^-1dispersion measurements in systems where the influence of paramagnetic impurities is negligible. Monte Carlo simulations of hydrated Q2D pores are executed for a range of surface-to-bulk desorption rates for a thin pore. G(t ) is found to decorrelate when spins move from the surface to the bulk, display three-dimensional properties at intermediate times, and finally show a bulk-mediated surface diffusion (L´evy) mechanism at longer times. The results may be used to interpret NMR relaxation rates in
hydrated porous systems in which the paramagnetic impurity density is negligible.
A probability density function describing the angular evolution of a fixed-length atom-atom vector as a Levy rotor is derived containing just two dynamical parameters: the Levy parameter α and a rotational time constant τ. A Levy parameter α < 2 signals anomalous (non-Brownian) motion. Molecular dynamics simulation of water at 298 K validates the probability density function for the intramolecular 1H─1H dynamics. The rotational dynamics of water is found to be approximately Brownian at sub-picosecond time intervals, becomes increasingly anomalous at longer time intervals due to hydrogen-bond breaking and reforming, before becoming indistinguishable from Brownian dynamics beyond about 25 ps. The Levy rotor model is used to estimate the intramolecular contribution to the longitudinal nuclear-magnetic resonance (NMR) relaxation rate R1;intra. It is found that R1;intra contributes 65% +/- 7% to the overall relaxation rate of water at room temperature.
A Brownian shell model describing the random rotational motion of a spherical shell of uniform particle density is presented and validated by molecular dynamics simulations. The model is applied to proton spin rotation in aqueous paramagnetic ion complexes to yield an expression for the Larmor-frequency-dependent nuclear magnetic resonance spin-lattice relaxation rate T1-1 (ω) describing the dipolar coupling of the nuclear spin of the proton with the electronic spin of the ion. The Brownian shell model provides a significant enhancement to existing particle-particle dipolar models without added complexity, allowing fits to experimental T1-1 (ω) dispersion curves without arbitrary scaling parameters. The model is successfully applied to measurements of T1 −1 (ω) from aqueous manganese(II), iron(III), and copper(II) systems where the scalar coupling contribution is known to be small. Appropriate combinations of Brownian shell and translational diffusion models, representing the inner and outer sphere relaxation contributions, respectively, are shown to provide excellent fits. Quantitative fits are obtained to the full dispersion curve of each aquoion with just five fit parameters, with the distance and time parameters each taking a physically justifiable numerical value.