Squeezing Oil into Water under Pressure: Inverting the Hydrophobic Effect

The molecular structure of dense homogeneous fluid water-methane mixtures has been determined for the first time using high-pressure neutron-scattering techniques at 1.7 and 2.2 GPa. A mixed state with a fully H-bonded water network is revealed. The hydration shell of the methane molecules is, however, revealed to be pressure-dependent with an increase in the water coordination between 1.7 and 2.2 GPa. In parallel, ab initio molecular dynamics simulations have been performed to provide insight into the microscopic mechanisms associated with the phenomenon of mixing. These calculations reproduce the observed phase change from phase separation to mixing with increasing pressure. The calculations also reproduce the experimentally observed structural properties. Unexpectedly, the simulations show mixing is accompanied by a subtle enhancement of the polarization of methane. Our results highlight the key role played by fine electronic effects on miscibility and the need to readjust our fundamental understanding of hydrophobicity to account for these

Structure and bonding of dense liquid oxygen from first principles simulations

Using first principles simulations we have investigated the structural and bonding properties of dense fluid oxygen up to 180 GPa. We have found that band gap closure occurs in the molecular liquid, with a "slow" transition from a semi-conducting to a poor metallic state occurring over a wide pressure range. At approximately 80 GPa, molecular dissociation is observed in the metallic fluid. Spin fluctuations play a key role in determining the electronic structure of the low pressure fluid, while they are suppressed at high pressure.Comment: 4 figure

Utilization of Methacrylates and Polymer Matrices for the Synthesis of Ion Specific Resins

Disposal, storage, and/or transmutation of actinides such as americium (Am) will require the development of specific separation schemes. Existing efforts focus on solvent extraction systems for achieving suitable separation of actinide from lanthanides. However, previous work has shown the feasibility of ion-imprinting polymer-based resins for use in ion-exchange-type separations with metal ion recognition. Phenolic-based resins have been shown to function well for Am-Eu separations, but these resins exhibited slow kinetics and difficulties in the imprinting process. This project addresses the need for new and innovative methods for the selective separation of actinides through novel ion-imprinted resins. The project team will explore incorporation of metals into extended frameworks, including the possibility of 3D polymerized matrices that can serve as a solid-state template for specific resin preparation. For example, an anhydrous trivalent f-element chain can be formed directly from a metal carbonate, and methacrylic acid from water. From these simple coordination complexes, molecules of discrete size or shape can be formed via the utilization of coordinating ligands or by use of an anionic multi-ligand system incorporating methacrylate. Additionally, alkyl methyl methacrylates have been used successfully to create template nanospaces, which underscores their potential utility as 3D polymerized matrices. This evidence provides a unique route for the preparation of a specific metal ion template for the basis of ion-exchange separations. Such separations may prove to be excellent discriminators of metal ions, even between f-elements

A node-based approach to charm-FFT

Parallel 3D Fast Fourier Transform is a communication intensive algorithm that suffers from the unignorable communication overhead. Because the interconnect communication bandwidth is a static component, adjustments to reduce or hide the necessary communication overheads are performed to obtain the optimal performance with a FFT grid in a given environment. In this thesis, an alternative method to an existing Parallel 3D FFT library was explored. The FFT library, Charm-FFT empowered by Charm++, was redesigned to utilize larger number of nodes while aiming to reduce the number of necessary communications between its components during its computations. Instead of decomposing the input FFT grid into the fine-grained objects that are distributed to the available PEs, coarser-grained decomposition method that only distributes to the available nodes was applied. As there are less number of receivers that each decomposed object communicates during the state transposition, the overall number of communication is reduced at the cost of parallelism from using the finer decomposition method. This loss of parallelism is attempted to be mitigated by applying within-node parallelism using multi-threading or accelerators. Lastly, to maintain the usability of the modified library when multiple FFT grid computations are needed with given resource, each FFT grid is assigned to a subset of the resource to compute and communicate only within its subset rather than to use all resource for each grid's computation