arXiv subjects

M. Bahadori

Publications and source records attributed to M. Bahadori.

4 recordsLinked to original sources

arXiv2006

Characterizing Phase Transitions in Liquid Cesium by a Soft-core and Large Attractive Equation of State

This paper investigates to identify phase transitions in condensed liquid cesium metal by considering the variation of intermolecular potential parameters εand r_m in the whole liquid range, with εbeing the potential well-depth and r_m the position of minimum potential. These parameters were obtained from the parameters of a new equation of state that was derived recently by using the characteristic potential function. By this method, transitions at about 575 K, 800 K, 1000 K, 1350 K and 1650 K were identified. Transitions at 575 K, 800 K, and 1000 K are weak but, the one at 1350 K is very significant and has been explored experimentally and theoretically as the metal non-metal transition (MNMT), which is a phase transition before the critical condition dominates the thermodynamics. Also variations of the linear correlation coefficient of the isotherms generate a spot point pattern of these transitions. Our observations at 575 K for εand r_m are in accord with the anomalies in adiabatic thermal coefficient of pressure, density, viscosity, electrical conductivity, and structure factor.

cond-mat.stat-mech↗

arXiv2006

Density dependent equations of state for metal, nonmetal, and transition states for compressed mercury fluid

Analytical equations of state are presented for fluid mercury in metal, nonmetal, and in metal-nonmetal transition states. Equations of state for metal and nonmetal states are simple in form but the complexities of transition state leads to a complex fourth-order equation. The interatomic potential function used to describe the metal state have a hard repulsive wall, and that of nonmetal state is the same as potential function of non-polar fluid with induced dipole intermolecular interaction. Metal-nonmetal transition occurs in the liquid density range 11-8 g/cm3, and a density dependent interaction potential which gradually changes from a pure metal interaction to a nonmetal interaction, on going from metal state to nonmetal state in the transition region, is used. Well-depth and the position of potential minimum are presented as temperature dependent quantities; their calculated values for the metal state are typically within 5.0% and 0.33% of the experimental value, respectively. The calculated well-depth for nonmetal state is smaller than the experimental value indicating the effect of high pressure PVT data used, which pushes a pair of mercury atom further together into the repulsive side. In the transition region, calculated well-depths are 2-3 order of magnitudes larger than for the metal state, and contain a sharp rising edge and a steep falling having a singularity characteristic of phase transition.

cond-mat.stat-mech↗

arXiv2005

New thermodynamic regularity for cesium over the whole liquid range

In this paper we derive an equation of state for liquid cesium based on a suggested potential function in accord to the characteristics large attraction and soft repulsion at the asymptotes of interaction potentials. By considering the interaction of nearest adjacent atoms in dense fluid, the equation of state predicts that the isotherm is linear function of, where is the compression factor, is the molar volume, and is the molar density. The linear parameters are identified as interaction coefficients related to attraction and repulsion, and are used to evaluate the molecular parameters with interesting implications. The isotherm is intended to resolve the particular thermodynamic properties of alkali metals, which have been known for their unusual change of the nature of intermolecular force as the characteristic metal-nonmetal transition range is approached. When applied to liquid cesium, the isotherms persist linear over the whole liquid range including the metal non-metals transition range and at the critical temperature perfectly. The isotherm is equivalent to a virial (like) EOS for which the linear parameters of the isotherm form the corresponding second and third virial coefficients. The new potential function turns out to be an effective potential that includes not only a pair interaction but also many-body interactions and therefore it is not always comparable with pair potential.

physics.chem-ph↗

arXiv2002

Common compression factor and bulk modulus quiescence points of liquid cesium

In this paper, a recently developed analytical equation of state (EOS) is used to investigate the bulk modulus of compressed liquid cesium and to locate common compression factor and the bulk modulus quiescence point(s). This EOS is applied quick well to Na and Rb far from Tc. Bulk modulus of liquid cesium have two quiescence points, a sharp one in the range 1100k-1500k and a diffused one in the range 1600k-1900k. Therefore, two types of liquid cesium metal may be identified with characteristic structure and interaction potential energy. It is a constant independent of temperature, however, some residual change is seen due to the change in the values of integral of pair correlation function as temperature is increased. Furthermore, it is related to the shape of the unit cell and the atomic size at equilibrium. Observation of distinct liquid in the metal-nonmetal transition range is compared with NMR studies and molecular dynamic results.

cond-mat.mtrl-sci↗