Crystallization of the Lewis–Wahnström <i>ortho</i>-terphenyl model

Pedersen, Ulf R.; Hudson, Toby; Harrowell, Peter

doi:10.1063/1.3559153

Cited by 14 publications

(27 citation statements)

References 68 publications

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“…This model is difficult to crystallize and easily supercooled. In the crystal the three LJ spheres sit near the sites of a BCC lattice of a crystal with cubatic orientational disorder, i.e., with the molecules aligning randomly along the three Cartesian axis 53 . When a system like this in a simulation is scaled to a different density, the rigid bond lengths are kept constant and only the distances between the molecules' centers of masses are scaled uniformly to the new density.…”

Section: Results For Five Other Model Crystalsmentioning

confidence: 99%

Isomorph invariance of the structure and dynamics of classical crystals

et al. 2014

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This paper shows by computer simulations that some crystalline systems have curves in their thermodynamic phase diagrams, so-called isomorphs, along which structure and dynamics in reduced units are invariant to a good approximation. The crystals are studied in a classical-mechanical framework, which is generally a good description except significantly below melting. The existence of isomorphs for crystals is validated by simulations of particles interacting via the Lennard-Jones pair potential arranged into a face-centered cubic (FCC) crystalline structure; the slow vacancyjump dynamics of a defective FCC crystal is also shown to be isomorph invariant. In contrast, a NaCl crystal model does not exhibit isomorph invariances. Other systems simulated, though in less detail, are the Wahnström binary Lennard-Jones crystal with the MgZn2 Laves crystal structure, monatomic FCC crystals of particles interacting via the Buckingham pair potential and via a novel purely repulsive pair potential diverging at a finite separation, an ortho-terphenyl molecular model, and SPC/E hexagonal ice. Except for NaCl and ice, the crystals simulated all have isomorphs. Based on these findings and previous simulations of liquid models, we conjecture that crystalline solids with isomorphs include most or all formed by atoms or molecules interacting via metallic or van der Waals forces, whereas covalently-or hydrogen-bonded crystals are not expected to have isomorphs. Crystals of ions or dipolar molecules constitute a limiting case for which isomorphs are only expected when the Coulomb interactions are relatively weak. We briefly discuss the consequences of the findings for theories of melting and crystallization.

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Section: Results For Five Other Model Crystalsmentioning

confidence: 99%

Isomorph invariance of the structure and dynamics of classical crystals

et al. 2014

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“…66 require a word of qualification. The Lennard-Jones mixture, along with a number of other popular models of glass formers, has recently 200,201 been shown to crystallize during extended simulation runs at a modest supercooling, indicating that they are not as good glass formers as previously assumed. More realistic models of metal alloys do not, to date, exhibit the same preponderance of a single local structural motif.…”

Section: B Structure Dynamics and The Limits Of The Liquid Statementioning

confidence: 98%

Perspective: Supercooled liquids and glasses

Ediger

Harrowell

2012

The Journal of Chemical Physics

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Supercooled liquids and glasses are important for current and developing technologies. Here we provide perspective on recent progress in this field. The interpretation of supercooled liquid and glass properties in terms of the potential energy landscape is discussed. We explore the connections between amorphous structure, high frequency motions, molecular motion, structural relaxation, stability against crystallization, and material properties. Recent developments that may lead to new materials or new applications of existing materials are described.

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“…The Lewis–Wahnström OTP model is an isosceles triangle with an angle of 75°, different from the 60° of the real 1,2-diphenylbenzene molecule. 36 …”

Section: Simulation Detailsmentioning

confidence: 99%

“…(c) Along an isotherm with 11% density increase. At the highest density probed the OTP model crystallizes 36 (magenta). Figure 17 shows the corresponding reduced molecular center-of-mass radial distribution functions. The reduced molecular center-of-mass structure is less invariant along the isomorph than for the asymmetric dumbbell (Figure 6), consistent with the OTP model being less strongly correlating ( R ≈ 0.90).…”

Section: Numerical Study Of Isomorphs For the Three Model Systemsmentioning

confidence: 99%

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Isomorphs in Model Molecular Liquids

2012

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Isomorphs are curves in the phase diagram along which a number of static and dynamic quantities are invariant in reduced units (Gnan, N.; et al. J. Chem. Phys.2009, 131, 234504). A liquid has good isomorphs if and only if it is strongly correlating, i.e., if the equilibrium virial/potential energy fluctuations are more than 90% correlated in the NVT ensemble. Isomorphs were previously discussed with a focus on atomic systems. This paper generalizes isomorphs to liquids composed of rigid molecules and study the isomorphs of systems of small rigid molecules: the asymmetric dumbbell model, a symmetric inverse power-law dumbbell, and the Lewis–Wahnström o-terphenyl (OTP) model. For all model systems, the following quantities are found to a good approximation to be invariant along an isomorph: the isochoric heat capacity, the excess entropy, the reduced molecular center-of-mass self-part of the intermediate scattering function, and the reduced molecular center-of-mass radial distribution function. In agreement with theory, we also find that an instantaneous change of temperature and density from an equilibrated state point to an isomorphic state point leads to no relaxation. The isomorphs of the Lewis–Wahnström OTP model were found to be more approximative than those of the asymmetric dumbbell model; this is consistent with the OTP model being less strongly correlating. The asymmetric dumbbell and Lewis–Wahnström OTP models each have a “master isomorph”; i.e., the isomorphs have identical shape in the virial/potential energy phase diagram.

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Crystallization of the Lewis–Wahnström ortho-terphenyl model

Cited by 14 publications

References 68 publications

Isomorph invariance of the structure and dynamics of classical crystals

Isomorph invariance of the structure and dynamics of classical crystals

Perspective: Supercooled liquids and glasses

Isomorphs in Model Molecular Liquids

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