Modeling<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi mathvariant="normal">In</mml:mi><mml:mo>−</mml:mo><mml:mi mathvariant="normal">Se</mml:mi></mml:mrow></mml:math>amorphous alloys

Koháry, K.; Burlakov, V. M.; Pettifor, D. G.; Nguyen-Manh, D.

doi:10.1103/physrevb.71.184203

Cited by 20 publications

(10 citation statements)

References 34 publications

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“…Noteworthy is the analysis of the material topology in terms of ring statistics . A ring is defined “as the shortest closed path through nearest‐neighbor atoms with each bond passed only once” 63. A predominance of even‐numbered rings was found in Ge 2 Sb 2 Te 5 .…”

Section: Structure and Bonding In The Crystalline And The Amorphoumentioning

confidence: 99%

Design Rules for Phase‐Change Materials in Data Storage Applications

2011

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Phase-change materials can rapidly and reversibly be switched between an amorphous and a crystalline phase. Since both phases are characterized by very different optical and electrical properties, these materials can be employed for rewritable optical and electrical data storage. Hence, there are considerable efforts to identify suitable materials, and to optimize them with respect to specific applications. Design rules that can explain why the materials identified so far enable phase-change based devices would hence be very beneficial. This article describes materials that have been successfully employed and dicusses common features regarding both typical structures and bonding mechanisms. It is shown that typical structural motifs and electronic properties can be found in the crystalline state that are indicative for resonant bonding, from which the employed contrast originates. The occurence of resonance is linked to the composition, thus providing a design rule for phase-change materials. This understanding helps to unravel characteristic properties such as electrical and thermal conductivity which are discussed in the subsequent section. Then, turning to the transition kinetics between the phases, the current understanding and modeling of the processes of amorphization and crystallization are discussed. Finally, present approaches for improved high-capacity optical discs and fast non-volatile electrical memories, that hold the potential to succeed present-day's Flash memory, are presented.

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Section: Structure and Bonding In The Crystalline And The Amorphoumentioning

confidence: 99%

Design Rules for Phase‐Change Materials in Data Storage Applications

2011

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“…An alternative to these finite element calculations is to employ direct models that can capture the spatial and time evolution of the crystallization process. Kohary et al 23 modelled the heterogeneous crystallization of phase‐change materials using a multi‐scale materials modelling approach, where the energetics of the underlying atomic structure is the driving force for the crystallization kinetics. This model predicts a linear dependence of the amorphous region lifetime upon the region size, which suggests that data storage applications based on phase‐change materials with heterogeneous crystallization properties could reach an order of magnitude higher density, but with an order of magnitude shortening in lifetime.…”

Section: Nanoscale Phase‐transformationmentioning

confidence: 99%

Modelling the phase‐transition in phase‐change materials

Koháry

Wright

2013

Physica Status Solidi (b)

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Phase‐change materials have a wide range of optical and electrical applications due to a unique combination of structural, electronic and optical properties. The phase transition between the crystalline and amorphous phases is a central physical process in devices based on phase‐change materials. In order to design and to develop future applications with novel functionalities we need to understand on the nanometre length scale and the (sub)nanosecond timescale the electrical, thermal and phase‐transition behaviour of phase‐change materials. At the nanoscale the phase‐transformation in phase‐change materials is governed by the chemical composition, atomic structure, and the input energy due to temperature (Joule heat), electric field and/or electronic excitations. Therefore, a successful phase‐change model should capture all these elements and predict the phase information as an output. We discuss the theoretical models that have been used to study and predict the crystallization of phase‐change materials that span the materials modelling spectrum from electronic/atomistic simulations (atomic behaviour) to microscopic and continuum models (bulk behaviour). Real applications and device design require the use of microscopic and continuum models due to large computational times of atomistic simulations. On the other hand the predictions provided by microscopic and continuum models depend on the chosen parameter set used to describe the phase transition. We stress the importance of ‘building bridges’ between atomistic and continuum modelling to design future phase‐change devices with novel and enhanced functionalities.

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“…15 The structure of amorphous In x Se 1−x with x = 0.4, 0.5, and 0.6 has been studied by a first-principles tight-binding MD technique. 16 In this study, we investigate the structure and electronic states of the liquid Tl-Se alloys by ab initio MD simulations. We give a detailed comparison of calculated results with the experimental data, and clarify the concentration dependence of the structural and bonding properties of the liquid Tl-Se alloys.…”

Section: Introductionmentioning

confidence: 99%

Concentration dependence of structural and bonding properties of liquid Tl-Se alloys byab initiomolecular dynamics simulations

Koura

Shimojo

2008

Phys. Rev. B

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The structural and electronic properties of liquid Tl x Se 1−x for 0 Յ x Յ 1 are investigated by means of ab initio molecular dynamics simulations. It is shown that calculated structure factors are in good agreement with experiments over the whole range of composition. It is confirmed from calculated electronic densities of states that the liquid Tl-Se alloys have semiconducting properties for Tl concentrations not exceeding the stoichiometric composition ͑x =2/ 3͒, while they are metallic for x Ͼ 2 / 3. In Se-rich composition range, Se atoms form chain molecules, whose average length becomes shorter with increasing Tl concentration. In the equiatomic liquid Tl-Se alloy, short Se chains, mostly negatively charged Se 2 dimers, coexist with a few Se ions, while most of Se atoms exist as ions at the stoichiometric composition. Based on a population analysis, we discuss the concentration dependence of the bonding properties in comparison with that in liquid alkali-metal chalcogenides.

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ModelingIn−Seamorphous alloys

Cited by 20 publications

References 34 publications

Design Rules for Phase‐Change Materials in Data Storage Applications

Design Rules for Phase‐Change Materials in Data Storage Applications

Modelling the phase‐transition in phase‐change materials

Concentration dependence of structural and bonding properties of liquid Tl-Se alloys byab initiomolecular dynamics simulations

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