Search results for "THERMODYNAMICS"
showing 10 items of 2774 documents
Characterization of theTiSiO4structure and its pressure-induced phase transformations: Density functional theory study
2009
Theoretical investigations concerning the possible titanium silicate polymorphs have been performed using density functional theory at B3LYP level. Total-energy calculations and geometry optimizations have been carried out for all phases involved. The following sequence of pressure-driven structural transitions has been found: ${\text{CrVO}}_{4}$-type, $Cmcm$ (in parenthesis the transition pressure), $\ensuremath{\rightarrow}$ zircon-type, $I{4}_{1}/amd$ (0.8 GPa), $\ensuremath{\rightarrow}$ scheelite-type, $I{4}_{1}/a$ (3.8 GPa). At higher pressure the last phase is found to be stable at least up to 25 GPa. The equation of state of the different polymorphs is also reported. We found that t…
Empirical molecular dynamics study of structural, elastic and thermodynamic properties of zinc-blende-like SiGe compound
2004
Abstract A three-body potential coupled with a molecular-dynamics method is used to calculate structural and thermodynamic properties of the hypothetical IV–IV compound SiGe in zinc-blende phase. A good agreement between the calculated and theoretical values of the lattice constant, the bulk modulus and its derivative, and the cohesive energy is obtained. We also compute the elastic constants, Debye temperature, lattice thermal expansion, and the specific heat. We investigate also, the structural properties of SiGe when rock-salt phase appears.
Enthalpies of solution and dilution of butanol and pentanol in dodecyltrimethylammonium bromide micellar solutions
1987
The enthalpies of solution and of dilution of 1-butanol and 1-pentanol were measured in micellar solutions of dodecyltrimethylammonium bromide by systematically changing the concentration of alcohols and surfactant. The enthalpies of solution at infinite dilution of alcohols at each surfactant concentration were evaluated from a linear plot. This quantity increases with surfactant concentration (up to 0.8m) with a curvature which depends on the alcohol alkyl chain length. The difficulties arising for a quantitative treatment of both the enthalpies of dilution and of solution at finite alcohol concentrations are discussed. The dependence on the surfactant concentration of the standard enthal…
Potential models for the simulation of methane adsorption on graphene: development and CCSD(T) benchmarks
2018
Different force fields for the graphene–CH4 system are proposed including pseudo-atom and full atomistic models. Furthermore, different charge schemes are tested to evaluate the electrostatic interaction for the CH4 dimer. The interaction parameters are optimized by fitting to interaction energies at the DFT level, which were themselves benchmarked against CCSD(T) calculations. The potentials obtained with both the pseudo-atom and full atomistic approaches describe accurately enough the average interaction in the methane dimer as well as in the graphene–methane system. Moreover, the atom–atom potentials also correctly provide the energies associated with different orientations of the molecu…
Effect of stiffness on the phase behavior of cubic lattice chains
2005
Gran canonica Monte Carlo (GCMC) simulazioni assistite da tecniche di riponderazione istogramma sono stati utilizzati per studiare l'effetto della flessibilità catena sul comportamento di soluzione fase di cubi catene reticolari corti con 4-32 segmenti. Ciò è stato fatto variando un parametro di rigidità gradualmente fino alla media calcolata end-to-end distanza avvicinato la lunghezza totale. Per entrambe le catene flessibili e rigide si è riscontrato che la temperatura critica, ottenuta tramite mista analisi dei campi di dimensioni finite, aumentata lunghezza della catena e la densità critica trasferisce a valori più bassi, in accordo con le osservazioni sperimentali. Il estrapolato lungh…
Molluscan Shell Proteins: Primary Structure, Origin, and Evolution
2007
In the last few years, the field of molluscan biomineralization has known a tremendous mutation, regarding fundamental concepts on biomineralization regulation as well as regarding the methods of investigation. The most recent advances deal more particularly with the structure of shell biominerals at nanoscale and the identification of an increasing number of shell matrix protein components. Although the matrix is quantitatively a minor constituent in the shell of mollusks (less than 5% w/w), it is, however, the major component that controls different aspects of the shell formation processes: synthesis of transient amorphous minerals and evolution to crystalline phases, choice of the calciu…
Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy
2014
Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic - yet decisive - question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used…
Third International Conference on the Biochemistry and Molecular Biology of Nitric Oxide
1998
Abstract Nitric Oxide Volume 2, No. 2, April 1998, contained abstracts for the Third International Conference on the Biochemistry and Molecular Biology of Nitric Oxide. The abstracts are not available on IDEAL.
CLASSIFICATION THEORY FOR PHASE TRANSITIONS
1993
A refined classification theory for phase transitions in thermodynamics and statistical mechanics in terms of their orders is introduced and analyzed. The refined thermodynamic classification is based on two independent generalizations of Ehrenfests traditional classification scheme. The statistical mechanical classification theory is based on generalized limit theorems for sums of random variables from probability theory and the newly defined block ensemble limit. The block ensemble limit combines thermodynamic and scaling limits and is similar to the finite size scaling limit. The statistical classification scheme allows for the first time a derivation of finite size scaling without reno…
Driven Brownian particle as a paradigm for a nonequilibrium heat bath: Effective temperature and cyclic work extraction
2017
We apply the concept of a frequency-dependent effective temperature based on the fluctuation-dissipation ratio to a driven Brownian particle in a nonequilibrium steady state. Using this system as a thermostat for a weakly coupled harmonic oscillator, the oscillator thermalizes according to a canonical distribution at the respective effective temperature across the entire frequency spectrum. By turning the oscillator from a passive "thermometer" into a heat engine, we realize the cyclic extraction of work from a single thermal reservoir, which is feasible only due to its nonequilibrium nature.