arXiv subjects

P. T. Cummings

Publications and source records attributed to P. T. Cummings.

6 recordsLinked to original sources

arXiv2025

Analytic solution of the multidensity Ornstein-Zernike equation for hard-sphere fluid with tetrahedral quadrupolar-like surface adhesion

We develop a multidensity formulation of the Ornstein-Zernike equation with Percus-Yevick closure for hard spheres with anisotropic surface adhesion of tetrahedral quadrupolar-like symmetry. An analytical solution is obtained using the invariant expansion method combined with Baxter's factorization technique. Structural properties are evaluated using both the multidensity theory and the previously proposed single-density molecular OZ approach. At low stickiness, the two theories yield nearly identical predictions, while increasing stickiness leads to growing discrepancies and eventual loss of convergence of the single-density approach. These results highlight the importance of multidensity descriptions for strongly associating anisotropic fluids.

cond-mat.soft↗

arXiv2019

Primitive models of room temperature ionic liquids. Liquid-gas phase coexistence

We propose several versions of primitive models of room temperature ionic liquids (RTILs) and develop a mean spherical approximation (MSA)-type theory for their description. RTIL is modeled as a two-component mixture of hard-sphere anions and flexible linear chain cations, represented by tangentially bonded hard spheres with the charge located on one of the terminal beads. The theoretical description of the model is carried out using the solution of the appropriately modified associative MSA (AMSA). Our solution reduces to solving one nonlinear algebraic equation for the Blum's screening parameter $Γ$, which in turn is used to express all thermodynamic properties of the models of interest. We calculate liquid-gas phase diagrams using theoretical and computer simulation methods for two versions of the model, represented by the dimer ($D$) and chain ($C$) models. Theoretical predictions for the phase diagrams appear to be in reasonably good agreement with computer simulation results. It is demonstrated that the models and theory are able to qualitatively reproduce experimentally observed phase behavior of RTILs, in particular the decrease of the critical temperature and critical density with increasing asymmetry of the model in its shape and position of the charge.

cond-mat.soft↗

arXiv2012

Liquid-gas phase behavior of polydisperse dipolar hard-sphere fluid: Extended thermodynamic perturbation theory for central force associating potential

The liquid-gas phase diagram for polydisperse dipolar hard-sphere fluid with polydispersity in the hard-sphere size and dipolar moment is calculated using extension of the recently proposed thermodynamic perturbation theory for central force (TPT-CF) associating potential. To establish the connection with the phase behavior of ferrocolloidal dispersions it is assumed that the dipole moment is proportional to the cube of the hard-sphere diameter. We present and discuss the full phase diagram, which includes cloud and shadow curves, binodals and distribution functions of the coexisting daughter phases at different degrees of the system polydispersity. In all cases studied polydispersity increases the region of the phase instability and shifts the critical point to the higher values of the temperature and density. The larger size particles always fractionate to the liquid phase and the smaller size particles tend to move to the gas phase. At relatively high values of the system polydispersity three-phase coexistence is observed.

cond-mat.soft↗

arXiv2011

Investigation of bone resorption within a cortical basic multicellular unit using a lattice-based computational model

In this paper we develop a lattice-based computational model focused on bone resorption by osteoclasts in a single cortical basic multicellular unit (BMU). Our model takes into account the interaction of osteoclasts with the bone matrix, the interaction of osteoclasts with each other, the generation of osteoclasts from a growing blood vessel, and the renewal of osteoclast nuclei by cell fusion. All these features are shown to strongly influence the geometrical properties of the developing resorption cavity including its size, shape and progression rate, and are also shown to influence the distribution, resorption pattern and trajectories of individual osteoclasts within the BMU. We demonstrate that for certain parameter combinations, resorption cavity shapes can be recovered from the computational model that closely resemble resorption cavity shapes observed from microCT imaging of human cortical bone.

q-bio.TO↗

arXiv2007

Phase coexistance in polydisperse mixture of hard-sphere colloidal and flexible chain particles

A theoretical scheme for the calculation of the full phase diagram (including cloud and shadow curves, binodals and distribution functions of the coexisting phases) for colloid-polymer mixtures with polymer chain length polydispersity and hard-sphere colloidal and polymeric monomer sizes polydispersity is proposed. The scheme combines thermodynamic perturbation theory for associating fluids and recently developed method used to determine the phase diagram of polydisperse spherical shape colloidal fluids (L.Bellier-Castella {\it et al.}, {\it J.Chem.Phys.} {\bf 113}, 8337(2000)). By way of illustration we present and discuss the full phase diagram for the mixture with polydispersity in the size of the hard-sphere colloidal particles.

cond-mat.soft↗

arXiv2001

Multicomponent mixture of charged hard-sphere chain molecules in the polymer mean-spherical approximation

The analytical solution of the recently proposed ideal chain polymer mean-spherical approximation (Yu.Kalyuzhnyi, Mol.Phys., 94, 735(1998)) is presented for the multicomponent mixture of charged hard-sphere linear chain flexible molecules. The solution apply to any mixture of chain molecules with arbitrary distribution of the charge and size of the beads along the molecular backbone. Closed form analytical expressions for the internal energy, Helmholtz free energy, chemical potentials and pressure are derived. By way of illustration thermodynamical properties of several versions of the fluid of charged chain molecules of different length, including the molecules with uniform, diblock and alternating distribution of the charge are studied. Theoretical predictions are in reasonable agreement with available computer simulation predictions. We present also the liquid-gas phase diagrams for the systems with diblock and alternating distribution of the charge.

cond-mat↗