<i>Ab initio</i>simulation of first-order amorphous-to-amorphous phase transition of silicon

Durandurdu, Murat; Drabold, D. A.

doi:10.1103/physrevb.64.014101

Cited by 93 publications

(102 citation statements)

References 48 publications

(43 reference statements)

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“…[72][73][74] Theoretical investigations have attempted to characterize these amorphous phases in bulk Si [73][74][75][76][77][78] and hydrogenated Si nanocrystals. [20][21][22][23][24] The LDA phase has been described as a disordered tetrahedrally coordinated network, the HDA as a deformed tetrahedral network 75 with the presence of interstitials increasing the coordination to 5-6, and finally a veryhigh-density amorphous phase (VHDA) has been postulated 78 with coordinations 8-9 as found also in ice. 79 This classification of the amorphous structures is adopted in this paper.…”

Section: Results: Pressure-induced Transformations In Silicon Nanmentioning

confidence: 99%

Simulations of nanocrystals under pressure: Combining electronic enthalpy and linear-scaling density-functional theory

Corsini

Greco

Hine

et al. 2013

The Journal of Chemical Physics

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We present an implementation in a linear-scaling density-functional theory code of an electronic enthalpy method, which has been found to be natural and efficient for the ab initio calculation of finite systems under hydrostatic pressure. Based on a definition of the system volume as that enclosed within an electronic density isosurface [M. Cococcioni, F. Mauri, G. Ceder, and N. Marzari, Phys. Rev. Lett. 94, 145501 (2005)], it supports both geometry optimizations and molecular dynamics simulations. We introduce an approach for calibrating the parameters defining the volume in the context of geometry optimizations and discuss their significance. Results in good agreement with simulations using explicit solvents are obtained, validating our approach. Size-dependent pressure-induced structural transformations and variations in the energy gap of hydrogenated silicon nanocrystals are investigated, including one comparable in size to recent experiments. A detailed analysis of the polyamorphic transformations reveals three types of amorphous structures and their persistence on depressurization is assessed.

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Section: Results: Pressure-induced Transformations In Silicon Nanmentioning

confidence: 99%

Simulations of nanocrystals under pressure: Combining electronic enthalpy and linear-scaling density-functional theory

Corsini

Greco

Hine

et al. 2013

The Journal of Chemical Physics

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“…[37,38] Silicon, which is characterized by a tetrahedrally coordinated network, as are the above materials, can also be expected to exhibit the phenomenon of polyamorphism. [39] In bulk amorphous silicon, the pressure-induced LDA-HDA transition was studied by density functional theory simulations, [40] where an irreversible first-order-like transition to a metallic phase was observed at about 16 GPa.…”

Section: Methodsmentioning

confidence: 99%

Polyamorphism in Silicon Nanocrystals under Pressure

Molteni

Martoňák

2005

ChemPhysChem

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The size and surface of semiconductor nanocrystals determine most of their properties: an accurate control of their shape and dimension allows one to design nanocrystals with desired features that can then be used individually, or suitably assembled, to create a range of interesting new materials.[1] Examples of size-dependent properties include the melting point [2] and the band gap. [3,4] The latter has recently been exploited for medical applications: nanocrystals of different sizes, which fluoresce with different colors, can be used for labeling biomolecules, as an alternative to conventional organic dye fluorophores. [4][5][6][7][8] At variance with conventional dyes, these materials are extremely photostable. Moreover, a single source can excite several colors: the absorption spectra are in fact very broad, while emission is confined to a narrow band centered at the wavelength characteristic of the specific nanocrystal size.Pressure-induced phase transformations in semiconductor nanocrystals also show a strong size dependence. In particular small nanocrystals, whose properties are not clearly dominated by their bulk core, but are strongly affected by their shape and surface, can show exotic behavior and novel mechanisms of phase transformations can be uncovered.Silicon, cadmium sulfide and cadmium selenide nanocrystals have been extensively studied under applied pressure by X-ray techniques and optical spectroscopy.[9-17] Pressure-induced structural transformations in semiconductor nanocrystals occur at a pressure higher than in the corresponding bulk crystals: the smaller the nanocrystal, the higher the transition pressure. When pressure is applied and then released a hysteretic behavior is observed; this could be exploited to trap the nanocrystals in metastable structures with nonconventional bonding arrangements, so to expand the range of available materials with different properties. Moreover, available experimental data for silicon indicate that the very effect of pressure also depends on the nanocrystal size: while large nanocrystals transform into different crystalline phases under pressure, [13] smallsized nanocrystallites, as found in porous silicon, amorphize. [18] Computer simulations, in particular at the ab initio level, have the potential to supply information complementary to experiments by providing an accurate microscopic description of the evolution of the atomic structures under applied pressure and of the mechanisms of phase transformations. Here we revisit our previous investigations of Si clusters [19,20] focusing on the polyamorphism phenomenon. MethodologyWhile constant-pressure molecular dynamics techniques for extended periodic systems, such as bulk crystals, are well established, [21,22] a novel molecular dynamics method to apply pressure to a finite, nonperiodic system (e.g. a nanocrystal) within an ab initio scheme had to be devised. Our methodology, which is inspired by experiments, consists in immersing a quantum-mechanically treated nanocrystal into a pressuretransmitting med...

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“…Si)=-107.71 eV, E min (ph-Si)=-107.68 eV, and E min (HDA)= -107.53 eV, as obtained from the studies in [23,24,31]. In the present study, B 0 and Bc are the bulk modulus and the pressure derivative of the bulk modulus for silicon with V min, respectively.…”

mentioning

confidence: 97%

“…An experiment has recently confirmed such a first order amorphous to amorphous phase transition [22]. Such calculations require candidate structures which may be obtained from constant pressure simulations and sometimes experiments [23,24]. In the present study, a theoretical model is developed …”

mentioning

confidence: 99%

“…Here, we examine the atomistic response to nanoindentation by a sharp indenter with various centerlineto-face angles α. From the stress response at incipient plasticity developed by Pan et al [13], the contact stress V c and indentation strain H c in Fig Stress-induced phase transitions in microcrystalline silicon (μc-Si) have been extensively studied [19][20][21][22][23][24]. In order to study the model of crystallization, the volume-dependent Gibbs free energy is evaluated.…”

mentioning

confidence: 99%

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The model developed for stress-induced structural phase transformations of micro-crystalline silicon films

Han

Lin

2010

Nano-Micro Lett.

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The nanoindentations were applied to island-shaped regions with metal-induced Si crystallizations. The experimental stress-strain relationship is obtained from the load-depth profile in order to investigate the critical stresses arising at various phase transitions. The stress and strain values at various indentation depths are applied to determine the Gibbs free energy at various phases. The intersections of the Gibbs free energy lines are used to determine the possible paths of phase transitions arising at various indentation depths. All the critical contact stresses corresponding to the various phase transitions at four annealing temperatures were found to be consistent with the experimental results. undergoes a direct transition from diamond to a simple hexagonal structure. One such prediction was a kinetically hindered first order amorphous to amorphous phase transition in SiO 2 [21]. An experiment has recently confirmed such a first order amorphous to amorphous phase transition [22]. Such calculations require candidate structures which may be obtained from constant pressure simulations and sometimes experiments [23,24]. In the present study, a theoretical model is developed

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Ab initiosimulation of first-order amorphous-to-amorphous phase transition of silicon

Cited by 93 publications

References 48 publications

Simulations of nanocrystals under pressure: Combining electronic enthalpy and linear-scaling density-functional theory

Simulations of nanocrystals under pressure: Combining electronic enthalpy and linear-scaling density-functional theory

Polyamorphism in Silicon Nanocrystals under Pressure

The model developed for stress-induced structural phase transformations of micro-crystalline silicon films

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