Solid-liquid transition in polydisperse Lennard-Jones systems

Sarkar, Sarmistha and Biswas, Rajib and Santra, Mantu and Bagchi, Biman (2013) Solid-liquid transition in polydisperse Lennard-Jones systems. In: PHYSICAL REVIEW E, 88 (2).

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Abstract

We study melting of a face-centered crystalline solid consisting of polydisperse Lennard-Jones spheres with Gaussian polydispersity in size. The phase diagram reproduces the existence of a nearly temperature invariant terminal polydispersity (delta(t) similar or equal to 0.11), with no signature of reentrant melting. The absence of reentrant melting can be attributed to the influence of the attractive part of the potential upon melting. We find that at terminal polydispersity the fractional density change approaches zero, which seems to arise from vanishingly small compressibility of the disordered phase. At constant temperature and volume fraction the system undergoes a sharp transition from crystalline solid to the disordered amorphous or fluid state with increasing polydispersity. This has been quantified by second- and third-order rotational invariant bond orientational order, as well as by the average inherent structure energy. The translational order parameter also indicates a similar sharp structural change at delta similar or equal to 0.09 in case of T* = 1.0, phi = 0.58. The free energy calculation further supports the sharp nature of the transition. The third-order rotationally invariant bond order shows that with increasing polydispersity, the local cluster favors a more icosahedral arrangement and the system loses its local crystalline symmetry. Interestingly, the value of structure factor S(k) of the amorphous phase at delta similar or equal to 0.10 (just beyond the solid-liquid transition density at T* = 1) becomes 2.75, which is below the value of 2.85 required for freezing given by the empirical Hansen-Verlet rule of crystallization, well known in the theory of freezing.

Item Type:	Journal Article
Publication:	PHYSICAL REVIEW E
Publisher:	AMER PHYSICAL SOC
Additional Information:	Copyright of this article is belongs to AMER PHYSICAL SOC
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	02 Oct 2013 05:45
Last Modified:	02 Oct 2013 05:45
URI:	http://eprints.iisc.ac.in/id/eprint/47350

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