arXiv subjects

Pai-Yi Hsiao

Publications and source records attributed to Pai-Yi Hsiao.

27 records · Page 2Linked to original sources

arXiv2008

Overcharging, charge inversion and reentrant condensation: Using highly-charged polyelectrolytes in tetravalent salt solutions as an example of study

We study salt-induced charge overcompensation and charge inversion of flexible polyelectrolytes via computer simulations and demonstrate the importance of ion excluded volume. Reentrant condensation takes place when the ion size is comparable to monomer size, and happens in a middle region of salt concentration. In a high-salt region, ions can overcharge a chain near its surface and charge distribution around a chain displays an oscillatory behavior. Unambiguous evidence obtained by electrophoresis shows that charge inversion does not necessarily appear with overcharging and occurs when the ion size is not big. These findings suggest a disconnection of resolubilization of polyelectrolyte condensates at high salt concentration with charge inversion.

cond-mat.soft↗

arXiv2007

Role of chain stiffness on the conformation of single polyelectrolytes in salt solutions

Conformation of single polyelectrolytes in tetravalent salt solutions is investigated under the framework of a coarse-grained model, using Langevin dynamics simulations. The chain size, studied by the radius of gyration, shows three different variational behaviors with salt concentration, depending on the chain stiffness. According to these behaviors, polyelectrolytes of fixed chain length are classified into three categories: flexible chain, semiflexible chain, and rigid chain. The worm-like chain model with persistence length predicted by the Odijk-Skolnick-Fixman theory is found to be able to qualitatively describe the end-to-end distance at low salt concentration. In a low-salt region, a flexible polyelectrolyte extends more significantly than a semiflexible chain, and in a high-salt region, regardless of chain stiffness, a chain attains a dimension comparable to that of its neutral polymer. The chain stiffness influences both the local and the global chain structures. A flexible chain exhibits a zigzagged local structure in the presence of salt ions and the condensed structure is a disordered, random globule. A semiflexible chain is locally smooth, and the condensed structure is orderly packed, taking a form such as hairpin or toroid. Moreover, the chain stiffness can also affect the nature of the coil-globule transition. The transition is occurred in a discrete manner for semiflexible chain, whereas in a continuous way for flexible chain. This discrete feature is happened not only at low salt concentration when a semiflexible chain is collapsed, but also at high salt concentration when the collapsed chain is reexpanded. At the end, the effects of chain stiffness and salt concentration on the conformation of single polyelectrolytes are summarized in a schematic state diagram.

cond-mat.soft↗

arXiv2006

Salt-induced collapse and reexpansion of highly charged flexible polyelectrolytes

We study the salt-dependent conformations of dilute flexible polyelectrolytes in solution via computer simulations. Low concentrations of multivalent salt induce the known conformational collapse of individual polyelectrolyte chains, but as the salt concentration is increased further this is followed by a reexpansion. We explicitly demonstrate that multivalent counterions can overcompensate the bare charge of the chain in the reexpansion regime. Both the degree of reexpansion and the occurrence of overcharging sensitively depend on ion size. Our findings are relevant for a wide range of salt-induced complexation phenomena.

cond-mat.soft↗

arXiv2006

Chain morphology, swelling exponent, persistence length, like-charge attraction, and charge distribution around a chain in polyelectrolyte solutions: effects of salt concentration and ion size studied by molecular dynamics simulations

Properties of polyelectrolytes in tetravalent salt solutions are intensively investigated by a coarse-grained model. The concentration of salt and the size of tetravalent counterions are found playing a decisive role on chain properties. If the size of tetravalent counterions is compatible with the one of monomers, the chains show extended structures at low and at high salt concentrations, whereas at intermediate salt concentrations, they acquire compact and prolate structures. The swelling exponent of a chain against salt concentration behaves in an analogous way as the morphological quantities. Under certain condition, the electrostatics gives a negative contribution to the persistence length, in companion with a salt-induced mechanical instability of polyelectrolytes. Nearly at the same moment, it appears like-charge attraction between chains. The equal size of the tetravalent ions and the monomers is the optimal condition to attain the strongest attraction between chains and the most compact chain structure. Moreover, the ions form a multi-layer organization around a chain and, thus, the integrated charge distribution reveals an oscillatory behavior. The results suggest that charge inversion has no direct connection with redissolution of polyelectrolytes at high salt concentrations.

cond-mat.soft↗

arXiv2003

Scaling law of Wolff cluster surface energy

We study the scaling properties of the clusters grown by the Wolff algorithm on seven different Sierpinski-type fractals of Hausdorff dimension $1 < d_f \le 3$ in the framework of the Ising model. The mean absolute value of the surface energy of Wolff cluster follows a power law with respect to the lattice size. Moreover, we investigate the probability density distribution of the surface energy of Wolff cluster and are able to establish a new scaling relation. It enables us to introduce a new exponent associated to the surface energy of Wolff cluster. Finally, this new exponent is linked to a dynamical exponent via an inequality.

cond-mat.stat-mech↗

arXiv2003

Critical behavior of the 3-state Potts model on Sierpinski carpet

We study the critical behavior of the 3-state Potts model, where the spins are located at the centers of the occupied squares of the deterministic Sierpinski carpet. A finite-size scaling analysis is performed from Monte Carlo simulations, for a Hausdorff dimension $d_{f}$ $\simeq 1.8928$. The phase transition is shown to be a second order one. The maxima of the susceptibility of the order parameter follow a power law in a very reliable way, which enables us to calculate the ratio of the exponents $γ/ν$. We find that the scaling corrections affect the behavior of most of the thermodynamical quantities. However, the sequence of intersection points extracted from the Binder's cumulant provides bounds for the critical temperature. We are able to give the bounds for the exponent $1/ν$ as well as for the ratio of the exponents $β/ν$, which are compatible with the results calculated from the hyperscaling relation.

cond-mat.stat-mech↗

arXiv2003

Critical Behavior of the Ferromagnetic Ising Model on a Sierpinski Carpet: Monte Carlo Renormalization Group Study

We perform a Monte Carlo Renormalization Group analysis of the critical behavior of the ferromagnetic Ising model on a Sierpiński fractal with Hausdorff dimension $d_f\simeq 1.8928$. This method is shown to be relevant to the calculation of the critical temperature $T_c$ and the magnetic eigen-exponent $y_h$ on such structures. On the other hand, scaling corrections hinder the calculation of the temperature eigen-exponent $y_t$. At last, the results are shown to be consistent with a finite size scaling analysis.

cond-mat.stat-mech↗

arXiv2000

Critical exponents of ferromagnetic Ising model on fractal lattices

We review the value of the critical exponents $ν^{-1}$, $β/ν$, and $γ/ν$ of ferromagnetic Ising model on fractal lattices of Hausdorff dimension between one and three. They are obtained by Monte Carlo simulation with the help of Wolff algorithm. The results are accurate enough to show that the hyperscaling law $d_f=2β/ν+γ/ν$ is satisfied in non-integer dimension. Nevertheless, the discrepancy between the simulation results and the $ε$-expansion studies suggests that the strong universality should be adapted for the fractal lattices.

cond-mat.stat-mech↗

arXiv2000

Acoustic coupling between two air bubbles in water

The acoustic coupling between two air bubbles immersed in water is clearly demonstrated. The system is acoustically forced, and its response is detected. The experimental results confirm that both theoretically predicted eigenmodes, respectively symmetrical and antisymmetrical, do exist. Their frequencies, measured as a function of the bubbles spacing, follow theoretical estimations within a 10% accuracy.

physics.class-ph↗