Chris has an undergraduate degree in Theoretical Physics and a PhD in Chemistry. Before joining UTS he was based at CSIRO in Hobart where he investigated the effects of ocean acidification on coral reefs. Prior to this he spent two years at Stanford University, developing new approaches for numerical simulation of light-induced chemical reactions.
Chris works across the Climate Change Cluster (C3), mostly within the Algal Biosystems and Biotechnology and Future Reefs programs.
Programming and scientific computing.
Data analysis and visualization
Zavřel, T, Szabó, M, Tamburic, B, Evenhuis, C, Kuzhiumparambil, U, Literáková, P, Larkum, AWD, Raven, JA, Červený, J & Ralph, PJ 2018, 'Effect of carbon limitation on photosynthetic electron transport in Nannochloropsis oculata.', Journal of photochemistry and photobiology. B, Biology, vol. 181, pp. 31-43.View/Download from: UTS OPUS or Publisher's site
This study describes the impacts of inorganic carbon limitation on the photosynthetic efficiency and operation of photosynthetic electron transport pathways in the biofuel-candidate microalga Nannochloropsis oculata. Using a combination of highly-controlled cultivation setup (photobioreactor), variable chlorophyll a fluorescence and transient spectroscopy methods (electrochromic shift (ECS) and P700 redox kinetics), we showed that net photosynthesis and effective quantum yield of Photosystem II (PSII) decreased in N. oculata under carbon limitation. This was accompanied by a transient increase in total proton motive force and energy-dependent non-photochemical quenching as well as slightly elevated respiration. On the other hand, under carbon limitation the rapid increase in proton motive force (PMF, estimated from the total ECS signal) was also accompanied by reduced conductivity of ATP synthase to protons (estimated from the rate of ECS decay in dark after actinic illumination). This indicates that the slow operation of ATP synthase results in the transient build-up of PMF, which leads to the activation of fast energy dissipation mechanisms such as energy-dependent non-photochemical quenching. N. oculata also increased content of lipids under carbon limitation, which compensated for reduced NAPDH consumption during decreased CO2 fixation. The integrated knowledge of the underlying energetic regulation of photosynthetic processes attained with a combination of biophysical methods may be used to identify photo-physiological signatures of the onset of carbon limitation in microalgal cultivation systems, as well as to potentially identify microalgal strains that can better acclimate to carbon limitation.
Tamburic, B, Evenhuis, CR, Crosswell, JR & Ralph, PJ 2018, 'An empirical process model to predict microalgal carbon fixation rates in photobioreactors', Algal Research, vol. 31, pp. 334-346.View/Download from: UTS OPUS or Publisher's site
© 2018 Elsevier B.V. An empirical process model was developed to infer the instantaneous net photosynthesis and carbon fixation rates from continuous pH and dissolved oxygen measurements during microalgal cultivation in photobioreactors. The model is based on the physical and chemical processes that govern the relationship between inorganic carbon supplied to a microalgal culture and the organic carbon fixed into microalgal biomass, with a particular focus on carbonate chemistry and mass transfer. Bayesian statistics were used to estimate the uncertainty in state variables, such as pH, net photosynthesis rate, and bicarbonate ion concentration, based on the constraints imposed by prior knowledge about these variables. The model was verified by batch-culturing the chlorophyte microalga Chlorella vulgaris in a photobioreactor under both bicarbonate-replete and bicarbonate-limiting conditions in order to test its predictive ability under different operational settings. The replicate photobioreactors were set up to simulate a scaled-down vertical cross-section of a typical raceway pond. This model could be used to test the activity and efficiency of carbon concentrating mechanisms in different microalgal species. It also provides a detailed understanding of how the rate of photosynthesis depends on dissolved inorganic carbon concentration, which could lead to better management of carbon supply in large-scale microalgal cultivation facilities.
Baker, KG, Radford, DT, Evenhuis, C, Kuzhiumparam, U, Ralph, PJ & Doblin, MA 2018, 'Thermal niche evolution of functional traits in a tropical marine phototroph.', Journal of phycology.View/Download from: UTS OPUS or Publisher's site
Land-based plants and ocean-dwelling microbial phototrophs known as phytoplankton, are together responsible for almost all global primary production. Habitat warming associated with anthropogenic climate change has detrimentally impacted marine primary production, with the effects observed on regional and global scales. In contrast to slower-growing higher plants, there is considerable potential for phytoplankton to evolve rapidly with changing environmental conditions. The energetic constraints associated with adaptation in phytoplankton are not yet understood, but are central to forecasting how global biogeochemical cycles respond to contemporary ocean change. Here, we demonstrate a number of potential trade-offs associated with high-temperature adaptation in a tropical microbial eukaryote, Amphidinium massartii (dinoflagellate). Most notably, the population became high-temperature specialized (higher fitness within a narrower thermal envelope and higher thermal optimum), and had a greater nutrient requirement for carbon, nitrogen and phosphorus. Evidently, the energetic constraints associated with living at elevated temperature alter competiveness along other environmental gradients. While high-temperature adaptation led to an irreversible change in biochemical composition (i.e., an increase in fatty acid saturation), the mechanisms underpinning thermal evolution in phytoplankton remain unclear, and will be crucial to understanding whether the trade-offs observed here are species-specific or are representative of the evolutionary constraints in all phytoplankton.
Langlais, CE, Lenton, A, Heron, SF, Evenhuis, C, Sen Gupta, A, Brown, JN & Kuchinke, M 2017, 'Coral bleaching pathways under the control of regional temperature variability', Nature Climate Change, vol. 7, no. 11, pp. 839-844.View/Download from: UTS OPUS or Publisher's site
Increasing sea surface temperatures (SSTs) are predicted to adversely impact coral populations worldwide through increasing thermal bleaching events. Future bleaching is unlikely to be spatially uniform. Therefore, understanding what determines regional differences will be critical for adaptation management. Here, using a cumulative heat stress metric, we show that characteristics of regional SST determine the future bleaching risk patterns. Incorporating observed information on SST variability, in assessing future bleaching risk, provides novel options for management strategies. As a consequence, the known biases in climate model variability and the uncertainties in regional warming rate across climate models are less detrimental than previously thought. We also show that the thresholds used to indicate reef viability can strongly influence a decision on what constitutes a potential refugia. Observing and understanding the drivers of regional variability, and the viability limits of coral reefs, is therefore critical for making meaningful projections of coral bleaching risk.
Tran, NAT, Seymour, JR, Siboni, N, Evenhuis, CR & Tamburic, B 2017, 'Photosynthetic carbon uptake induces autoflocculation of the marine microalga Nannochloropsis oculata', Algal Research, vol. 26, pp. 302-311.View/Download from: UTS OPUS or Publisher's site
© 2017 Elsevier B.V. Microalgal biomass has been used to produce biofuels, aquaculture feed, high-value chemicals such as pigments and antioxidants, and even human food. This study addresses one of the key bottlenecks to the commercialisation of microalgal bioproducts: the high energy and environmental cost of harvesting microalgal cells out of suspension. An innovative and sustainable autoflocculation procedure was developed to pre-concentrate microalgal biomass for easier har vesting. Microalgal cell agglomeration by autoflocculation at high pH was induced for the first time, without the addition of a chemical flocculant, in the commercially-relevant microalga Nannochloropsis oculata. Photosynthetic inorganic carbon uptake, in the absence of carbon dioxide supply by mass transfer, was used to raise the culture pH. Autoflocculation started at pH 9.5 and reached a maximum flocculation efficiency of 90% at pH 10.4. Microalgal surface charge-neutralisation by calcium cations, and sweep flocculation by calcium carbonate and calcium phosphate precipitates were identified as the dominant flocculation mechanisms. This was also the first study to measure changes in bacterial community composition under autoflocculation. There was a clear shift from free-living bacteria in suspension to attached bacteria during autoflocculation, with Flavobacteriales becoming the dominant order of bacteria. This highlights the influential role of attached bacteria and bacteria-produced extracellular polymeric substances in microalgal flocculation. This study shows that regulating carbon dioxide supply is a promising green alternative to traditional microalgal flocculation processes as it alleviates the requirement for costly and harmful chemical flocculants and brings us closer to sustainable microalgal bioproducts.
Camp, EF, Dong, LF, Suggett, DJ, Smith, DJ, Boatman, TG, Crosswell, JR, Evenhuis, C, Scorfield, S, Walinjkar, A, Woods, J & Lawson, T 2017, 'A novel membrane inlet-infrared gas analysis (MI-IRGA) system for monitoring of seawater carbonate system', Limnology and Oceanography: Methods, vol. 15, no. 1, pp. 38-53.View/Download from: UTS OPUS or Publisher's site
© 2016 The Authors Limnology and Oceanography: Methods published by Wiley Periodicals, Inc. Increased atmospheric CO 2 concentrations are driving changes in ocean chemistry at unprecedented rates resulting in ocean acidification, which is predicted to impact the functioning of marine biota, in particular of marine calcifiers. However, the precise understanding of such impacts relies on an analytical system that determines the mechanisms and impact of elevated pCO 2 on the physiology of organisms at scales from species to entire communities. Recent work has highlighted the need within experiments to control all aspects of the carbonate system to resolve the role of different inorganic carbon species on the physiological responses observed across taxa in real-time. Presently however, there are limited options available for continuous quantification of physiological responses, coupled with real-time calculation of the seawater carbonate chemistry system within microcosm environments. Here, we describe and characterise the performance of a novel pCO 2 membrane equilibrium system (the Membrane Inlet Infra-Red Gas Analyser, MI-IRGA) integrated with a continuous pH and oxygen monitoring platform. The system can detect changes in the seawater carbonate chemistry and determine organism physiological responses, while providing the user with real-time control over the microcosm system. We evaluate the systems control, response time and associated error, and demonstrate the flexibility of the system to operate under field conditions and within a laboratory. We use the system to measure physiological parameters (photosynthesis and respiration) for the corals Pocillipora damicornis and Porites cylindrica; in doing so we present a novel dataset examining the interactive role of temperature, light and pCO 2 on the physiology of P. cylindrica.
Camp, EF, Smith, DJ, Evenhuis, C, Enochs, I, Manzello, D, Woodcock, S & Suggett, DJ 2016, 'Acclimatization to high-variance habitats does not enhance physiological tolerance of two key Caribbean corals to future temperature and pH.', Proceedings. Biological sciences, vol. 283, no. 1831.View/Download from: UTS OPUS or Publisher's site
Corals are acclimatized to populate dynamic habitats that neighbour coral reefs. Habitats such as seagrass beds exhibit broad diel changes in temperature and pH that routinely expose corals to conditions predicted for reefs over the next 50-100 years. However, whether such acclimatization effectively enhances physiological tolerance to, and hence provides refuge against, future climate scenarios remains unknown. Also, whether corals living in low-variance habitats can tolerate present-day high-variance conditions remains untested. We experimentally examined how pH and temperature predicted for the year 2100 affects the growth and physiology of two dominant Caribbean corals (Acropora palmata and Porites astreoides) native to habitats with intrinsically low (outer-reef terrace, LV) and/or high (neighbouring seagrass, HV) environmental variance. Under present-day temperature and pH, growth and metabolic rates (calcification, respiration and photosynthesis) were unchanged for HV versus LV populations. Superimposing future climate scenarios onto the HV and LV conditions did not result in any enhanced tolerance to colonies native to HV. Calcification rates were always lower for elevated temperature and/or reduced pH. Together, these results suggest that seagrass habitats may not serve as refugia against climate change if the magnitude of future temperature and pH changes is equivalent to neighbouring reef habitats.
Baker, KG, Robinson, CM, Radford, DT, McInnes, AS, Evenhuis, C & Doblin, MA 2016, 'Thermal performance curves of functional traits aid understanding of thermally induced changes in diatom-mediated biogeochemical fluxes', Frontiers in Marine Science, vol. 3, pp. 1-14.View/Download from: UTS OPUS or Publisher's site
© 2016 Baker, Robinson, Radford, McInnes, Evenhuis and Doblin.How the functional traits (FTs) of phytoplankton change with temperature is important for understanding the impacts of ocean warming on phytoplankton mediated biogeochemical fluxes. This study quantifies the thermal performance curves (TPCs) of FTs in the cosmopolitan model diatom, Thalassiosira pseudonana, to advance understanding of trade-offs between physiological (photoacclimation, carbon fixation, nitrate, phosphate, and silicate uptake) and morphological traits (cell volume and frustule silicification). We show that each FT has substantial phenotypic plasticity and exhibits a unique TPC, varying in both shape and thermal optimum, and diverging from the growth response. The TPC for growth was symmetric with a thermal optimum (Topt) of 18°C. In comparison, the TPC for primary productivity was warm-skewed with a Topt around 21°C, whereas frustule silicification decreased linearly with increasing temperature. Together, this suggests that the optimal temperature for overall fitness is a balance of trade-offs in the underlying functional traits. Moreover, these results demonstrate that growth is not necessarily an accurate estimate of overall biogeochemical performance and that temperature change will likely influence elemental fluxes such as carbon and silicon. Finally, we show that temperature-driven changes in individual traits e.g., photoacclimation, can mimic responses experienced under other environmental stressors (high light) and so a multi-trait assessment is essential for accurate interpretation of the cellular impact of warming. This study also reveals that multi-trait analysis, in the context of TPCs, provides insight into the cellular physiology regulating the whole cell response and has the potential to provide better estimates of how diatom-mediated biogeochemical fluxes are likely to be impacted in the context of ocean warming. Analyzing the response of multiple traits more comprehensiv...
Tran, NAT, Padula, MP, Evenhuis, CR, Commault, AS, Ralph, PJ & Tamburic, B 2016, 'Proteomic and biophysical analyses reveal a metabolic shift in nitrogen deprived Nannochloropsis oculata', Algal Research, vol. 19, pp. 1-11.View/Download from: UTS OPUS or Publisher's site
© 2016. The microalga Nannochloropsis oculata is a model organism for understanding intracellular lipid production, with potential benefits to the biofuel, aquaculture and nutraceutical industries. It is well known that nitrogen deprivation increases lipid accumulation in microalgae but the underlying processes are not fully understood. In this study, detailed proteomic and biophysical analyses were used to describe mechanisms that regulate carbon partitioning in nitrogen-deplete N. oculata. The alga selectively up- or down-regulated proteins to shift its metabolic flux in order to compensate for deficits in nitrate availability. Under nitrogen deprivation, proteins involved in photosynthesis, carbon fixation and chlorophyll biosynthesis were all down-regulated, and this was reflected in reduced cell growth and chlorophyll content. Protein content was reduced 4.9-fold in nitrogen-deplete conditions while fatty acid methyl esters increased by 60%. Proteomic analysis revealed that organic carbon and nitrogen from the breakdown of proteins and pigments is channeled primarily into fatty acid synthesis. As a result, the fatty acid concentration increased and the fatty acid profile became more favorable for algal biodiesel production. This advancement in microalgal proteomic analysis will help inform lipid accumulation strategies and optimum cultivation conditions for overproduction of fatty acids in N. oculata.
Evenhuis, C, Lenton, A, Cantin, NE & Lough, JM 2015, 'Modelling coral calcification accounting for the impacts of coral bleaching and ocean acidification', Biogeosciences, vol. 12, no. 9, pp. 2607-2630.View/Download from: UTS OPUS or Publisher's site
© Author(s) 2015. Coral reefs are diverse ecosystems that are threatened by rising CO2 levels through increases in sea surface temperature and ocean acidification. Here we present a new unified model that links changes in temperature and carbonate chemistry to coral health. Changes in coral health and population are explicitly modelled by linking rates of growth, recovery and calcification to rates of bleaching and temperature-stress-induced mortality. The model is underpinned by four key principles: the Arrhenius equation, thermal specialisation, correlated up- and down-regulation of traits that are consistent with resource allocation trade-offs, and adaption to local environments. These general relationships allow this model to be constructed from a range of experimental and observational data. The performance of the model is assessed against independent data to demonstrate how it can capture the observed response of corals to stress. We also provide new insights into the factors that determine calcification rates and provide a framework based on well-known biological principles to help understand the observed global distribution of calcification rates. Our results suggest that, despite the implicit complexity of the coral reef environment, a simple model based on temperature, carbonate chemistry and different species can give insights into how corals respond to changes in temperature and ocean acidification.
Siboni, N, Abrego, D, Evenhuis, C, Logan, M & Motti, CA 2015, 'Adaptation to local thermal regimes by crustose coralline algaedoes not affect rates of recruitment in coral larvae', Coral Reefs, vol. 34, pp. 1243-1253.View/Download from: UTS OPUS or Publisher's site
Crustose coralline algae (CCA) are well known for their ability to induce settlement in coral larvae. While their wide distribution spans reefs that differ substantially in temperature regimes, the extent of local adaptation to these regimes and the impact they have on CCA inductive ability are unknown. CCA Porolithon onkodes from Heron (southern) and Lizard (northern) islands on Australia's Great Barrier Reef (separated by 1181 km) were experimentally exposed to acute or prolonged thermal stress events and their thermal tolerance and recruitment capacity determined. A sudden onset bleaching model was developed to determine the health status of CCA based on the rate of change in the CCA live surface area (LSA). The interaction between location and temperature was significant (F (2,119) = 6.74, p = 0.0017), indicating that thermally driven local adaptation had occurred. The southern population remained healthy after prolonged exposure to 28 °C and exhibited growth compared to the northern population (p = 0.022), with its optimum temperature determined to be slightly below 28 °C. As expected, at the higher temperatures (30 and 32 °C) the Lizard Island population performed better that those from Heron Island, with an optimum temperature of 30 °C. Lizard Island CCA displayed the lowest bleaching rates at 30 °C, while levels consistently increased with temperature in their southern counterparts. The ability of those CCA deemed thermally tolerant (based on LSA) to induce Acropora millepora larval settlement was then assessed. While spatial differences influenced the health and bleaching levels of P. onkodes during prolonged and acute thermal exposure, thermally tolerant fragments, regardless of location, induced similar rates of coral larval settlement. This confirmed that recent thermal history does not influence the ability of CCA to induce settlement of A. millepora larvae.
Suggett, DJ, Goyen, S, Evenhuis, C, Szabo, M, Pettay, DT, Warner, ME & Ralph, PJ 2015, 'Functional diversity of photobiological traits within the genus Symbiodinium appears to be governed by the interaction of cell size with cladal designation', New Phytologist, vol. 208, no. 2, pp. 370-381.View/Download from: UTS OPUS or Publisher's site
© 2015 New Phytologist Trust. Dinoflagellates of the genus Symbiodinium express broad diversity in both genetic identity (phylogeny) and photosynthetic function to presumably optimize ecological success across extreme light environments; however, whether differences in the primary photobiological characteristics that govern photosynthetic optimization are ultimately a function of phylogeny is entirely unresolved. We applied a novel fast repetition rate fluorometry approach to screen genetically distinct Symbiodinium types (n = 18) spanning five clades (A-D, F) for potential phylogenetic trends in factors modulating light absorption (effective cross-section, reaction center content) and utilization (photochemical vs dynamic nonphotochemical quenching; [1 - C] vs [1 - Q]) by photosystem II (PSII). The variability of PSII light absorption was independent of phylogenetic designation, but closely correlated with cell size across types, whereas PSII light utilization intriguingly followed one of three characteristic patterns: (1) similar reliance on [1 - C] and [1 - Q] or (2) preferential reliance on [1 - C] (mostly A, B types) vs (3) preferential reliance on [1 - Q] (mostly C, D, F types), and thus generally consistent with cladal designation. Our functional trait-based approach shows, for the first time, how Symbiodinium photosynthetic function is governed by the interplay between phylogenetically dependent and independent traits, and is potentially a means to reconcile complex biogeographic patterns of Symbiodinium phylogenetic diversity in nature.
Tamburic, B, Evenhuis, CR, Suggett, DJ, Larkum, AWD, Raven, JA & Ralph, PJ 2015, 'Gas Transfer Controls Carbon Limitation During Biomass Production by Marine Microalgae', CHEMSUSCHEM, vol. 8, no. 16, pp. 2727-2736.View/Download from: UTS OPUS or Publisher's site
Evenhuis, C & Martínez, TJ 2011, 'A scheme to interpolate potential energy surfaces and derivative coupling vectors without performing a global diabatization.', The Journal of chemical physics, vol. 135, no. 22, p. 224110.View/Download from: Publisher's site
Simulation of non-adiabatic molecular dynamics requires the description of multiple electronic state potential energy surfaces and their couplings. Ab initio molecular dynamics approaches provide an attractive avenue to accomplish this, but at great computational expense. Interpolation approaches provide a possible route to achieve flexible descriptions of the potential energy surfaces and their couplings at reduced expense. A previously developed approach based on modified Shepard interpolation required global diabatization, which can be problematic. Here, we extensively revise this previous approach, avoiding the need for global diabatization. The resulting interpolated potentials provide only adiabatic energies, gradients, and derivative couplings. This new interpolation approach has been integrated with the ab initio multiple spawning method and it has been rigorously validated against direct dynamics. It is shown that, at least for small molecules, constructing an interpolated PES can be more efficient than performing direct dynamics as measured by the total number of ab initio calculations that are required for a given accuracy.
Evenhuis, CR & Manthe, U 2011, 'Photodissociation of CH3I: A Full-Dimensional (9D) Quantum Dynamics Study', Journal of Physical Chemistry A, vol. 115, no. 23, pp. 5992-6001.View/Download from: UTS OPUS or Publisher's site
The photodissociation of methyl iodide in the A band is studied by full-dimensional (9D) wave packet dynamics calculations using the multiconfigurational time-dependent Hartree approach. The potential energy surfaces employed are based on the diabatic potentials of Xie et al. [J. Phys. Chem. A 2000, 104, 1009] and the vertical excitation energy is taken from recent ab initio calculations [Alekseyev et al. J. Chem. Phys. 2007, 126, 234102]. The absorption spectrum calculated for exclusively parallel excitation agrees well with the experimental spectrum of the A band. The electronic population dynamics is found to be strongly dependent on the motion in the torsional coordinate related to the H-3-C-I bend, which presumably is an artifact of the diabatic model employed. The calculated fully product state-selected partial spectra can be interpreted based on the reflection principle and suggests strong coupling between the C-I stretching and the H-3-C-I bending motions during the dissociation process. The computed rotational and vibrational product distributions typically reproduce the trends seen in the experiment In agreement with experiment, a small but significant excitation of the total symmetric stretching and the asymmetric bending modes of the methyl fragment can be seen. In contrast, the umbrella mode of the methyl is found to be too highly excited in the calculated distributions.
Lenhardt, JM, Ong, MT, Choe, R, Evenhuis, CR, Martinez, TJ & Craig, SL 2010, 'Trapping a diradical transition state by mechanochemical polymer extension', Science, vol. 329, no. 5995, pp. 1057-1060.View/Download from: UTS OPUS or Publisher's site
Transition state structures are central to the rates and outcomes of chemical reactions, but their fleeting existence often leaves their properties to be inferred rather than observed. By treating polybutadiene with a difluorocarbene source, we embedded
Evenhuis, CR & Collins, MA 2009, 'Locally optimized coordinates in modified shepard interpolation', Journal of Physical Chemistry A, vol. 113, no. 16, pp. 3979-3987.View/Download from: UTS OPUS or Publisher's site
An extension of the modified Shepard interpolation method is presented that allows expansions for the potential energy using different local coordinate sets to be used in a global interpolation. The coordinates used in a given Taylor expansion are determined using a training set of geometries at which the ab initio potential energy is known and that is built up during the construction of the interpolated potential energy surface. The method is applied to the bound state potential energy surface of methanol and a significant improvement in the rate of convergence of the interpolated potential energy surface to the ab initio potential energy is observed.
Perriman, AW, Henderson, MJ, Evenhuis, CR, McGillivray, DJ & White, JW 2008, 'Effect of the air-water interface on the structure of lysozyme in the presence of guanidinium chloride', Journal of Physical Chemistry B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical, vol. 112, no. 31, pp. 9532-9539.View/Download from: UTS OPUS or Publisher's site
We report observations of the changes in the surface structure of lysozyme adsorbed at the air-water interface produced by the chemical denaturant guanidinium chloride. A primary result is the durability of the adsorbed surface layer to denaturation, as compared to the molecule in the bulk solution. Data on the surface film were obtained from X-ray and neutron reflectivity measurements and modeled simultaneously. The behavior of lysozyme in G.HCl solutions was determined by small-angle X-ray scattering. For the air-water interface, determination of the adsorbed protein layer dimensions shows that at low to moderate denaturant concentrations (up to 2 mol L-1), there is no significant distortion of the proteins tertiary structure at the interface, as changes in the orientation of the protein are sufficient to model data. At higher denaturant concentrations, time-dependent multilayer formation occurred, indicating molecular aggregation at the surface. Methodologies to predict the protein orientation at the interface, based on amino acid residues surface affinities and charge, were critiqued and validated against our experimental data.
Evenhuis, CR & Manthe, U 2008, 'Calculating vibrational spectra using modified Shepard interpolated potential energy surfaces', Journal of Chemical Physics, vol. 129, no. 2, p. 024104.View/Download from: UTS OPUS or Publisher's site
A potential energy interpolation approach based on modified Shepard interpolation and specifically designed for calculation of vibrational states is presented. The importance of the choice of coordinates for the rate of convergence is demonstrated. Studying the vibrational states of the water molecule as a test case, a coordinate system comprised of inverse bond distances and trigonometric functions of the bond angle is found to be particularly efficient. Different sampling schemes used to locate the reference points in the modified Shepard interpolation are investigated. A final scheme is recommended, which allows the construction of potential energy surfaces to sub-wave-number accuracy.
Viel, A, Eisfeld, W, Evenhuis, CR & Manthe, U 2008, 'Photoionization-induced dynamics of the ammonia cation studied by wave packet calculations using curvilinear coordinates', Chemical Physics, vol. 347, no. 1-3, pp. 331-339.View/Download from: UTS OPUS or Publisher's site
The determination of the photoelectron spectrum of NH(3) and of the internal conversion dynamics of NH(3)(+) recently published [A. Viel, W. Eisfeld, S. Neumann, W. Domcke, U. Manthe, J. Chem. Phys. 124 (2006) 214306] is complemented by the investigation
Evenhuis, C, Nyman, G & Manthe, U 2007, 'Quantum dynamics of the CH3 fragment: a curvilinear coordinate system and kinetic energy operators.', The Journal of chemical physics, vol. 127, no. 14, p. 144302.View/Download from: Publisher's site
A curvilinear coordinate system for AB(3) fragments is given. The corresponding exact kinetic energy operator is derived and a series of simpler, progressively more approximate kinetic energy operators are suggested. The operators are tailored for quantum dynamics simulations using the multiconfigurational time-dependent Hartree approach. It is outlined how these fragment coordinates can be utilized to set up coordinate systems for larger systems such as AB(3)C or AB(3)CD. Calculations of the vibrational levels of CH(3) and quantum dynamics studies investigate the accuracy of the different kinetic energy operators suggested.
Godsi, O, Evenhuis, CR & Collins, MA 2006, 'Interpolation of multidimensional diabatic potential energy matrices', Journal of Chemical Physics, vol. 125, pp. 104105-0.View/Download from: Publisher's site
A method for constructing diabatic potential energy matrices by interpolation of ab initio quantum chemistry data is described and tested. This approach is applicable to any number of interacting electronic states, and relies on a formalism and a computa
Evenhuis, CR, Lin, X, Zhang, DH, Yarkony, D & Collins, MA 2005, 'Interpolation of diabatic potential-energy surfaces: Quantum dynamics on ab initio surfaces', Journal of Chemical Physics, vol. 123, pp. 134110-0.View/Download from: Publisher's site
A method for constructing diabatic potential-energy matrices from ab initio quantum chemistry data is described and tested for use in exact quantum reactive scattering. The method is a refinement of that presented in a previous paper, in that it accounts
A method is presented for constructing diabatic potential energy matrices from ab initio quantum chemistry data. The method is similar to that reported previously for single adiabatic potential energy surfaces, but correctly accounts for the nuclear permutation symmetry of diabatic potential energy matrices and other complications that arise from the derivative coupling of electronic states. The method is tested by comparison with an analytic model for the two lowest energy states of H(3).