Termodinámica del fluido de pozo cuadrado: efectos no conformales
The equilibrium between vapour and liquid in a square-well system has been determined by a hybrid simulation approach combining chemical potentials calculated via the Gibbs ensemble Monte Carlo technique with pressures calculated by the standard NV T Monte Carlo method. The phase equilibrium was det...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2009 |
| País: | México |
| Institución: | Universidad Autónoma Metropolitana |
| Repositorio: | Repositorio Institucional de la UAM Iztapalapa |
| Idioma: | español |
| OAI Identifier: | oai:bindani.izt.uam.mx:70795780f |
| Acceso en línea: | https://doi.org/10.24275/uami.70795780f |
| Access Level: | acceso abierto |
| Palabra clave: | info:eu-repo/classification/LEM/Ecuaciones de estado info:eu-repo/classification/LEM/Equilibrio líquido-vapor info:eu-repo/classification/LEM/Thermodynamics info:eu-repo/classification/LEM/Termodinámica info:eu-repo/classification/LEM/Vapor-liquid equilibrium info:eu-repo/classification/LEM/Física info:eu-repo/classification/LEM/Dinámica de fluidos info:eu-repo/classification/LEM/Fluid dynamics info:eu-repo/classification/LEM/Equations of state info:eu-repo/classification/LEM/Physics info:eu-repo/classification/cti/1 |
| Sumario: | The equilibrium between vapour and liquid in a square-well system has been determined by a hybrid simulation approach combining chemical potentials calculated via the Gibbs ensemble Monte Carlo technique with pressures calculated by the standard NV T Monte Carlo method. The phase equilibrium was determined from the thermodynamic conditions of equality of pressure and chemical potential between the two phases. The results of this hybrid approach were tested by independent NPT and μPT calculations and are shown to be of much higher accuracy than those of conventional GEMC simulations. The coexistence curves, vapour pressures and critical points were determined for SW systems of interaction ranges λ= 1.25, 1.5, 1.75 and 2. The new results show a systematic dependence on the range λ, in agreement with results from perturbation theory where previous work had shown more erratic behaviour. The free energy of square-well systems of hard-core diameter σ with ranges 1 ≤λ ≤3 is expanded in a perturbation series. This interval covers most ranges of interest, from short- ranged SW fluids (λ ' 1.2) used in modeling colloids to long ranges (1 λ ' 3) where the van der Waals classic approximation holds. The first four terms are evaluated by means of extensive Monte Carlo simulations. The calculations are corrected for the thermodynamic limit and care is taken to evaluate and control the various sources of error. The results for the first two terms in the series confirm well-known independent results but have an increased estimated accuracy and cover a wider set of well ranges. The results for the third- and fourth-order terms are novel. The free-energy expansion for systems with short and intermediate ranges, 1 ≤ λ ≤ 2, is seen to have properties similar to those of systems with longer ranges, 2≤λ ≤ 3. An equation of state, (EOS), is built to represent the free-energy data. The equilibrium between vapour and liquid in a square-well system has been determined by a hybrid simulation approach combining chemical potentials calculated via the Gibbs ensemble Monte Carlo technique with pressures calculated by the standard NV T Monte Carlo method. The phase equilibrium was determined from the thermodynamic conditions of equality of pressure and chemical potential between the two phases. The results of this hybrid approach were tested by independent NPT and μPT calculations and are shown to be of much higher accuracy than those of conventional GEMC simulations. The coexistence curves, vapour pressures and critical points were determined for SW systems of interaction ranges λ= 1.25, 1.5, 1.75 and 2. The new results show a systematic dependence on the range λ, in agreement with results from perturbation theory where previous work had shown more erratic behaviour. The free energy of square-well systems of hard-core diameter σ with ranges 1 ≤λ ≤3 is expanded in a perturbation series. This interval covers most ranges of interest, from short- ranged SW fluids (λ ' 1.2) used in modeling colloids to long ranges (1 λ ' 3) where the van der Waals classic approximation holds. The first four terms are evaluated by means of extensive Monte Carlo simulations. The calculations are corrected for the thermodynamic limit and care is taken to evaluate and control the various sources of error. The results for the first two terms in the series confirm well-known independent results but have an increased estimated accuracy and cover a wider set of well ranges. The results for the third- and fourth-order terms are novel. The free-energy expansion for systems with short and intermediate ranges, 1 ≤ λ ≤ 2, is seen to have properties similar to those of systems with longer ranges, 2≤λ ≤ 3. An equation of state, (EOS), is built to represent the free-energy data. |
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