On the first-order collapse transition of a three-dimensional, flexible homopolymer chain model

Rampf, Federica; Paul, Wolfgang; Binder, Kurt

doi:10.1209/epl/i2004-10520-y

Cited by 93 publications

(134 citation statements)

References 36 publications

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“…Interestingly, our results tend to have many more similarities with the work from Rampf et al [6][7][8] using the bond fluctuation model, especially with regards to the their latest work [8]. This is particularly true for the solid-liquid transition, where a sharp peak in the specific heat is seen at low temperature.…”

Section: Discussionsupporting

confidence: 85%

“…Each data set is shown over a distinct energy range, where the minimum energy boundary, E min /N, varies with chain length, but the maximum energy boundary is fixed at E max /N = 0.0 for all chain lengths. The maximum energy was initially set to zero based on the work from Rampf et al [6][7][8] and Parsons and Williams [10,11]. The minimum energy was "pushed" as low as it was possible to simulate efficiently, i.e.…”

Section: Simulation Resultsmentioning

confidence: 99%

“…Rampf et al [6][7][8] used the bondfluctuation model [9] to study single chain properties, while Parsons and Williams [10,11] used a continuous homopolymer model. Both models had simple interaction potentials and both studies found coil-globule and solid-liquid transitions.…”

Section: Introductionmentioning

confidence: 99%

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Developments in Wang-Landau simulations of a simple continuous homopolymer

Seaton¹,

Mitchell²,

Landau³

2008

Braz. J. Phys.

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The Wang-Landau method is used to study thermodynamic properties of a three-dimensional flexible homopolymer chain with continuous monomer positions. Results describing the coil-globule and solid-liquid transitions are presented for chain lengths up to N = 100. In order to elucidate the thermodynamic behavior, finite chain length effects and the influence of the energy range over which the density of states is determined are carefully analyzed. Simulation efficiency is also studied and it is shown that setting the natural logarithm of the final modification factor equal to 10 −6 is an appropriate choice for this model.

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Section: Discussionsupporting

confidence: 85%

Section: Simulation Resultsmentioning

confidence: 99%

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Developments in Wang-Landau simulations of a simple continuous homopolymer

Seaton¹,

Mitchell²,

Landau³

2008

Braz. J. Phys.

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“…Since the density of states g͑E͒ is independent of temperature, it encapsulates a system's behavior, such as internal energy U͑T͒, at all temperatures in the one calculation. The heat capacity may be readily computed as C V = dU / dT, and phase transitions such as the solid-liquid melting point may be identified by peaks in C V ͑T͒.A calculation of this nature studying the coil-globule transition of flexible homopolymers was recently performed by Rampf et al,4 who used a lattice model with a squarewell interaction energy between monomers. They measured the solid-liquid and coil-globule transition temperatures and concluded that in the thermodynamic limit, the two transition temperatures coincide, with the swollen coil bypassing the liquid globule and collapsing directly to the solid globule.…”

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confidence: 99%

An off-lattice Wang-Landau study of the coil-globule and melting transitions of a flexible homopolymer

Parsons

Williams

2006

The Journal of Chemical Physics

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The Wang-Landau Monte Carlo approach is applied to the coil-globule and melting transitions of off-lattice flexible homopolymers. The solid-liquid melting point and coil-globule transition temperatures are identified by their respective peaks in the heat capacity as a function of temperature. The melting and theta points are well separated, indicating that the coil-globule transition occurs separately from melting even in the thermodynamic limit. We also observe a feature in the heat capacity between the coil-globule and melting transitions which we attribute to a transformation from a low-density liquid globule to a high-density liquid globule. Since the density of states g͑E͒ is independent of temperature, it encapsulates a system's behavior, such as internal energy U͑T͒, at all temperatures in the one calculation. The heat capacity may be readily computed as C V = dU / dT, and phase transitions such as the solid-liquid melting point may be identified by peaks in C V ͑T͒.A calculation of this nature studying the coil-globule transition of flexible homopolymers was recently performed by Rampf et al.,4 who used a lattice model with a squarewell interaction energy between monomers. They measured the solid-liquid and coil-globule transition temperatures and concluded that in the thermodynamic limit, the two transition temperatures coincide, with the swollen coil bypassing the liquid globule and collapsing directly to the solid globule.Independently we have been pursuing a similar study. We have implemented 5 the Wang-Landau algorithm using an off-lattice model incorporating a finitely extensible nonlinear elastic ͑FENE͒ bond potential between neighboring bonded monomers, E bond =−KR 2 ln͑1−͑͑l − l 0 ͒ / ͑l max − l 0 ͒͒ 2 ͒, and a Lennard-Jones two-body potential between all monomers. The average bond length was l 0 = 0.7, bound in the range l ͑0.4, 1.0͒ with spring constant K = 20. The Lennard-Jones parameters were aligned so that the LennardJones energy minimum coincided with the FENE bond length, i.e., = l 0 /2 1/6 and = 1. The microcanonical ensemble average of a range of values including the radius of gyration and the core density ͑defined as the number of monomers in a sphere of radius 2.5 around the monomer closest to the polymer's centre of mass͒ were calculated for each energy bin E and converted to a canonical ensemble average, e.g., ͗R g 2 ͑T͒͘, using the density of states. Calculations were performed for N between 50 and 300. The density of states g͑E͒ was determined within the range E ͓ −4N ,0͒, which allows temperature behavior to be determined in the range T ͑0.5, 3͒, wide enough to cover the transitions described here. Sample densities of states for N = 100, 200, and 300 are given in Fig. 1, shifted to a common value of 2000 at E =0. Heat capacity curves C V ͑T͒ generated from the density of states for Nϭ100, 200, and 300 are shown in Fig. 2. Repeated calculations at each N are given, each based on a different starting configuration of the polymer. Constraints in the computer time available mean the...

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“…Monte Carlo methods have shown great promise in studying polymer conformation problems [1]. In particular, a wide variety of Monte Carlo methods have been applied to single chain polymer systems that include flexibility [2][3][4]. Many of these types of studies consider the bond fluctuation model [5], in which the monomer positions are confined to a lattice.…”

Section: Introductionmentioning

confidence: 99%