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Full-Text Articles in Chemistry
Monte Carlo Simulation Of The Solid To Super Liquid Phase Transition Of Langmuir Monolayers Using Cross-Section Potentials, D.R. Swanson, Robert J. Hardy, Craig J. Eckhardt
Monte Carlo Simulation Of The Solid To Super Liquid Phase Transition Of Langmuir Monolayers Using Cross-Section Potentials, D.R. Swanson, Robert J. Hardy, Craig J. Eckhardt
Craig J. Eckhardt Publications
A cross-section potential which models the interaction of two planar objects of prescribed shape is developed and used to model the interactions of amphiphiles in vertical phases of Langmuir monolayers. The results of Monte Carlo simulations of an isobaric-isothermal ensemble show qualitative agreement with experiment. The model system undergoes a continuous, bound-to-free rotator transition between phases of the same symmetries as the solid (S) and super liquid (LS) phases exhibited by fatty acid films.
Piezomodulated-Raman-Spectroscopy Study Of The Phase Transition In Phenothiazine, J. Sartwell, Craig J. Eckhardt
Piezomodulated-Raman-Spectroscopy Study Of The Phase Transition In Phenothiazine, J. Sartwell, Craig J. Eckhardt
Craig J. Eckhardt Publications
Single crystals of phenothiazine undergo a displacive order-disorder phase transition near 250 K. The microscopic mechanism of this transition is not clear owing to the complexity of a disordered lattice and the lack of direct mode-anharmonicity data. Unstable optical modes have been observed in phenothiazine and are regarded as coupled, by symmetry, to an acoustic mode that becomes overdamped through the phase transition. The latter is considered to have the primary role in the phase transition. This premise is in doubt, however, based on the optical-mode anharmonicity directly observed by uniaxial-piezomodulation-Raman-spectroscopy results presented here. Anharmonic responses are observed in the …
Brillouin-Scattering Study Of The Elastic Constants Of Phenothiazine Through The Phase Transition, J. Sartwell, Craig J. Eckhardt
Brillouin-Scattering Study Of The Elastic Constants Of Phenothiazine Through The Phase Transition, J. Sartwell, Craig J. Eckhardt
Craig J. Eckhardt Publications
It has been proposed that single crystals of phenothiazine undergo a proper ferroelastic phase transition: Pnma(D2h)→P21/c (C2h). This premise is in conflict with Brillouin-scattering studies from both quasi- and high-symmetry longitudinal and transverse acoustic modes reported here. The C55 elastic constant of phenothiazine as an orthorhombic crystal at ambient conditions shows no temperature dependence. The inelastic, light-scattering spectra support an order-disorder phase transition; no significantly unstable acoustic phonons were observed through the phase transition. Laser diffraction from structural domains reveals that the crystal is polysynthetically …
Investigation Of The Β-Γ Phase Transition In Single Crystal Malononitrile By Polarized Raman Spectroscopy, S.J. Bonafede, Craig J. Eckhardt
Investigation Of The Β-Γ Phase Transition In Single Crystal Malononitrile By Polarized Raman Spectroscopy, S.J. Bonafede, Craig J. Eckhardt
Craig J. Eckhardt Publications
Temperature dependent, polarized Raman spectra in the lattice mode region for sublimed, single crystal malononitrile through the β-γ phase transition (Tc=294.7 K) are reported. Symmetry assignments and frequencies of vibrational modes are made and compared to previous studies. Nine out of 12 possible lattice modes are observed in each phase with three of the observed modes being affected by the phase transition. The temperature dependence of these three affected modes is attributed to cyano group and molecular dipole interactions between molecules in the crystal. The behavior of malononitrile through the β-γ phase transition is analogous to the …