Viscosity

Bansal, Narottam P.; Doremus, Robert H.

doi:10.1016/b978-0-08-052376-7.50012-6

Cited by 12 publications

(6 citation statements)

References 38 publications

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“…270 alkali ions. The size of the simulation boxes was set according to experimental densities 37 , resulting in V (x = 0) : V (x = 0.5) : V (x = 1) = 1 : 1.03 : 1.06. In 33 the experimental densities for the two SA systems could be reproduced from NpT-simulations at identical pressure.…”

Section: Technical Aspectsmentioning

confidence: 99%

Contributions to the mixed-alkali effect in molecular dynamics simulations of alkali silicate glasses

Lammert¹,

Heuer²

2005

Phys. Rev. B

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The mixed-alkali effect on the cation dynamics in silicate glasses is analyzed via molecular dynamics simulations. Observations suggest a description of the dynamics in terms of stable sites mostly specific to one ionic species. As main contributions to the mixed-alkali slowdown longer residence times and an increased probability of correlated backjumps are identified. The slowdown is related to the limited accessibility of foreign sites. The mismatch experienced in a foreign site is stronger and more retarding for the larger ions, the smaller ions can be temporarily accommodated. Also correlations between unlike as well as like cations are demonstrated that support cooperative behavior.

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Section: Technical Aspectsmentioning

confidence: 99%

Contributions to the mixed-alkali effect in molecular dynamics simulations of alkali silicate glasses

Lammert¹,

Heuer²

2005

Phys. Rev. B

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“…The density is thus the experimental one, i.e. 2.38 g cm −3 [12]. The interaction potential used in our simulations is a modified version of the one proposed by Kramer et al [13] and its complete description can be found in [11].…”

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confidence: 99%

Characterization of channel diffusion in a sodium tetrasilicate glass via molecular-dynamics simulations

2002

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We study the structural and dynamical characteristics of the sodium atoms inside and outside the "diffusion channels" in glassy Na2O-4SiO2 (NS4) using classical molecular dynamics. We show that on average neither energetic arguments nor local environment considerations can explain the increased density of sodium atoms inside the subspace made of the channels. Nevertheless we show that at low temperature the mean square displacement of the sodium atoms inside this subspace is significantly larger than the one of the atoms outside the channels.PACS numbers: 61.20. Ja, 61.43.Fs, 66.30.Hs The diffusion of alkali atoms in silicate glasses is an important matter under investigation since several years. In particular the properties of sodium atoms inside the amorphous tetrahedral network of silica have been the topic of both experimental work [1] and moleculardynamics simulations (MD) [2] since a simple glass like Na 2 O-4SiO 2 (NS4) can be used as a prototype for more complicated glasses. The question of how the alkali atoms diffuse inside the glassy network is still a matter of debate and a generally accepted theory of ion transport in glasses is still missing [3,4]. In a previous MD study of NS4 we have shown that the ions follow preferential pathways ("channels") inside the glassy matrix [5]. Nevertheless contrarily to the popular idea proposed by Greaves [6] and developed in further studies [7], these channels are neither static nor due to a microsegregation of the sodium atoms but have to be seen dynamically in the sense that the channels are those regions of space in which a great number of sodiums have passed during a given simulation time. The existence of these channels gives rise to a pre-peak in the structure factor at around q = 0.95Å −1 seen both in experiments [8] and classical MD simulations [9]. In this last paper Horbach et al. show that the slow dynamics of the sodium atoms is closely related to the one of the underlying silica matrix which is coherent with the fact that there exists a strong correlation between the channels and the location of the non-bridging oxygen atoms, as shown in previous MD studies [10,11]. Once the existence of the channels is established, the next step is naturally to analyze their characteristics and to determine why the sodium atoms take these preferential pathways. This is the aim of the present study. In that direction we analyze the potential energy and the local structure of the sodium atoms whether they are INside the channels (Na In ) or OUTside the channels (Na Out ). It is indeed generally believed that the diffusion of the ions occurs via "hopping motions between well-defined potential minima" [4] which we should be able to detect in our simulations. We analyze also the time evolution of the sodium densities inside and outside the channels which permits us to detect the dynamics of the channels as a function of temperature and to quantify the differences between the sodium densities, differences that so far have only been suggested [9]. To elucidate the diffu...

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“…where Δp is the property change (here, thermal expansion coefficient), f i is the thermal expansion of constituent, i, and w i is the molar weight of constituent, i [23]. Fig.…”

Section: Experimental Setup and Resultsmentioning

confidence: 99%

Linearly polarized ytterbium-doped fiber laser in a pedestal design with aluminosilicate inner cladding

et al. 2011

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Ytterbium-doped polarization-maintaining fiber in a pedestal geometry is demonstrated using MCVD and a novel in-situ doping technique. The aluminosilicate pedestal layers minimize the thermal expansion mismatch against the silica outer cladding and permits complete freedom of location for the stress-applying parts in the fiber. A birefringence of 2.4×10 −4 is experimentally determined. The fiber delivers linearly polarized laser exhibiting 79% slope efficiency with a polarization extinction ratio of 12 dB.Output power, W

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Viscosity

Cited by 12 publications

References 38 publications

Contributions to the mixed-alkali effect in molecular dynamics simulations of alkali silicate glasses

Contributions to the mixed-alkali effect in molecular dynamics simulations of alkali silicate glasses

Characterization of channel diffusion in a sodium tetrasilicate glass via molecular-dynamics simulations

Linearly polarized ytterbium-doped fiber laser in a pedestal design with aluminosilicate inner cladding

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