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  • 1
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    High-pressure behavior of 3.65 Å phase: Insights from Raman spectroscopy (2023)
    In:  American Mineralogist
    Details
    Publication Date: 2023-08-07
    Description: The 3.65 Å phase [MgSi(OH)6] is a hydrous phase that is predicted to be stable in a simplified MgO-SiO2-H2O (MSH) ternary system at pressures exceeding 9 GPa. Along cold subduction zones, it is likely to transport water, bound in its crystalline lattice, into the Earth’s interior. The 3.65 Å phase consists of Mg and Si octahedral sites attached to the hydroxyl group that forms a hydrogen bond and is predicted to undergo pressure-induced symmetrization of the hydrogen bond. Therefore, in this study, we investigate the high-pressure behavior of the 3.65 Å phase using Raman spectroscopy. We have conducted five distinct compressions up to ~60 GPa using two different pressure-transmitting media—alcohol mixture and neon. At ambient conditions, we identified vibrational modes using complementary first-principles simulations based on density functional perturbation theory. Upon compression, we note that the first derivative of the vibrational modes in the lattice region stiffens, i.e., bilattice 〉 0. In contrast, the hydroxyl region softens, i.e., biOH 〉 0. This is indicative of the strengthening of hydrogen bonding upon compression. We noticed a significant broadening of vibrational modes related to hydroxyl groups that are indicative of proton disorder. However, within the maximum pressures explored in this study, we did not find evidence for pressure-induced symmetrization of the hydrogen bonds. We used the pressure derivative of the vibrational modes to determine the ratio of the bulk moduli and their pressure derivative. We note that the smaller bulk moduli of hydrous phases compared to the major mantle phases are compensated by significantly larger pressure derivatives of the bulk moduli for the hydrous phases. This leads to a significant reduction in the elasticity contrast between hydrous and major mantle phases. Consequently, the detection of the degree of mantle hydration is likely to be challenging at greater depths.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 2
    Electronic Resource
    Electronic Resource
    Computation of flow through a fluid-sediment interface in a benthic chamber (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 11 (1999), S. 1395-1405 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper we present a single-domain approach for the solution of flow in a composite region made up of a pure fluid layer and an underlying saturated porous layer. As an example, we compute the unsteady, axisymmetric flow and scalar transport in a stationary cylindrical container with a rotating lid, filled to the midheight with a porous material and to the top with water. A generalized equation known as the Brinkman-extended Darcy equation is solved inside the porous medium, along with the incompressible Navier–Stokes equations in the upper fluid layer. Comparisons with experimental data previously obtained by the authors for flow in the same geometry show good agreement, thus verifying the accuracy of the present computations. The results indicate that a single-domain approach can provide good predictions of interfacial flow, thereby obviating the need for ad hoc interface conditions. The existence of a thin Brinkman layer below the interface is observed. Radial profiles of computed velocity components adjacent to the interface show remarkable similarity, despite vast differences in magnitudes, showing that good matching between the two different flows has been achieved by the present single-domain approach. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870004
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  • 3
    Electronic Resource
    Electronic Resource
    A theory for Landau damping of ion acoustic waves in dope plasma (2001)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 8 (2001), S. 713-718 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Landau damping, free from the influence of other forms of damping, has been experimentally detected in ion acoustic waves in traces of a dope plasma of a light inert gas, when it is introduced into partially ionized plasma of a heavy inert gas. A theory has been worked out of Landau damping for longitudinal waves in Vlasov plasma for study of this and other familiar Landau dampings. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1339834
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  • 4
    Electronic Resource
    Electronic Resource
    Self-consistent T-matrix solution and computer-simulated velocity averaging approaches for the effective elastic constants of monoclinic polycrystals (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 4043-4047 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The self-consistent T-matrix solution envisaged by the effective-medium approach [R. Zeller and P. H. Dederichs, Phys. Status Solidi B 55, 831 (1973)] has, in general, led to a considerable clarification of our understanding of the mechanical properties of a variety of disorder systems including polycrystals. Specifically, the relevant formulations have been developed for cubic polycrystals by Zeller and Dederichs, and for hexagonal, tetragonal, trigonal, and orthorhombic polycrystals by T. R. Middya and A. N. Basu [J. Appl. Phys. 59, 2368 (1986)]. The present work on monoclinic polycrystals is a sequel to our previous work. We have developed the complete set of equations within the framework of the effective medium theory which delivers in a self-consistent manner the effective elastic constants of a monoclinic polycrystal in terms of those of the single crystal data. For comparison we have also evaluated the same quantities for each polycrystal by the computer simulation employing the velocity averaging process developed by T. R. Middya, A. N. Basu, and S. Sengupta [J. Appl. Phys. 57, 1844 (1985)]. Finally the results obtained by the above approaches for eight different polycrystals are compared with each other and also with other existing theoretical calculations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336709
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  • 5
    Electronic Resource
    Electronic Resource
    Multiple-scattering theoretic approach to the thermal expansion of inhomogeneous materials (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1166-1172 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Expression for the effective thermal expansion coefficient (TEC) of statistically homogeneous and isotropic, inhomogeneous material has been derived within the framework of the multiple-scattering theory. Then, from the general expression, effective TEC is obtained in the single-grain scattering approximation, for this type of materials, consisting of piecewise homogeneous phases (grains). For simplicity, only spherical grains are considered. Previous exact results for two-phase composites and polycrystals with crystallites having a preferred axis (e.g., tetragonal, trigonal, and hexagonal) are shown to follow from this approach in the single-grain scattering approximation. Apart from this, it is shown that the effective TEC for general multiphase composites and polycrystals can be obtained in a self-consistent way. Finally, the self-consistent solutions thus obtained have been employed to calculate the effective TEC of polycrystals belonging to different symmetry classes, and the results are found to compare favorably with observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341879
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  • 6
    Electronic Resource
    Electronic Resource
    Multiple scattering theoretical and computer simulated dynamic model approaches to effective elastic properties of randomly disordered composites (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2376-2381 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In the present investigation we have generalized the result obtained in the preceding paper [J. Appl. Phys. 59, 2368 (1985)] to treat composites containing crystallites of different crystal symmetries and arbitrary values of the elastic constants. This result has been used to discuss the existing theories intended to solve the same problem. An interesting finding of this analysis is that the present approach provides a single framework to discuss all the previous results which are particular cases of the general formulas derived here. Earlier all these cases were treated separately employing different approaches. Next we apply our results to six different binary composites and we find that our predictions compare quite favorably with experiment. For comparison we also calculate the same quantities by simulating the composite on a computer by the dynamic method originally developed by [T. R. Middya, A. N. Basu, and S. Sengupta [J. Appl. Phys. 57, 1844 (1985)] to discuss monocomponent polycrystal elastic properties. The two sets of results agree with each other for small differences in elastic properties of the components of a composite. But for larger differences, they diverge. Since the two approaches are based on widely different assumptions and the overall agreement of the effective-medium theory is distinctly superior, it appears that the existing experiments are consistent with the assumptions of the multiple scattering theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336337
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  • 7
    Electronic Resource
    Electronic Resource
    Self-consistent T-matrix solution for the effective elastic properties of noncubic polycrystals (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 2368-2375 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The multiple scattering theory has been a powerful tool in estimating the effective elastic properties of polycrystalline substances and different types of composite materials in terms of the component elastic properties. Both perturbative and self-consistent solutions within the framework of multiple scattering theory have been developed for cubic polycrystals by R. Zeller and P. H. Dederichs [Phys. Status. Solidi B 55, 831 (1973)]. Recently we have suggested [T. R. Middya, Mala Paul, and A. N. Basu, J. Appl. Phys. 58, 4095 (1985)] a perturbative method of calculation for all the noncubic polycrystals up to orthorhombic symmetry. Although the method has been quite successful in dealing with noncubic polycrystals with low anisotropy factors, it becomes too complex to handle the high anisotropy cases. Moreover, the results for many crystals for such cases with perturbation carried up to second order are inconsistent as they fall outside the well-known Hashin–Shtrikman (H–S) bounds. In order to overcome this difficulty, in this work we discuss a self-consistent T-matrix solution for the effective elastic properties of hexagonal, tetragonal, trigonal, and orthorhombic polycrystals. Within the approximation of multiple scattering of all orders from a single grain, we have obtained the self-consistent solution by exploiting the symmetry of each class. Next we have employed the formulas thus obtained to calculate the effective bulk and shear moduli of hexagonal, tetragonal, trigonal, and orthorhombic polycrystals. Finally the results are compared with our previous perturbative calculations, the H–S bounds and experiment. Unlike the previous calculations, all the self-consistent results fall within the H–S bounds. In addition to providing simple analytical formulas which can tackle polycrystals with arbitrary values of anisotropy factors, these formulas may also be used for evaluation of mechanical properties of composites having components belonging to different symmetries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336336
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  • 8
    Electronic Resource
    Electronic Resource
    Static and computer-simulated dynamic model approaches to effective elastic properties of noncubic polycrystals (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 4095-4101 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Based on the static deformation scheme envisaged by the effective medium theory developed by Zeller and Dederichs [Phys. Status Solidi B 55, 831 (1973)] formally similar to that of the quantum mechanical multiple scattering method, we have deduced a general expression for determining the effective elastic properties of any single component polycrystalline substance. From these general formulas using appropriate symmetry for the component crystallite the expressions for cubic, hexagonal, tetragonal, trigonal, and orthorhombic polycrystals may be easily derived. Two sets of approximate formulae are given and their ranges of validity discussed. For comparison with this static approach, we have also calculated the same quantities by simulating the polycrystal on a computer using the dynamic model developed by Middya, Basu, and Sengupta [J. Appl. Phys. 57, 1844 (1985)]. The results obtained by these two approaches based on entirely different assumptions are remarkably close to each other and to experiment for twenty-four different noncubic polycrystalline specimens considered in the present investigation. In fact, for the effective rigidity modulus, the agreement between the two methods is within 1% in all cases except for two specimens. The reasons for this discrepancy are discussed. However, while the computer simulation provides a very simple method for evaluating the effective elastic properties of polycrystals with high accuracy, it raises a question regarding the relation between the apparently contradictory assumptions on which the static and the dynamic methods are based. Finally, an experiment is suggested that may be helpful in resolving this difficulty.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.335539
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  • 9
    Electronic Resource
    Electronic Resource
    Self-consistent T-matrix solution for the effective elastic properties of perfectly disordered multiphase solids (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 58 (1985), S. 1809-1813 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-consistent solution for the effective elastic properties of polycrystalline and perfectly disordered multiphase composites has been discussed by using the T-matrix method under certain suitable approximations. Compared to the existing formulas these new relations for the disordered composites are very useful in practical situations for a quick and more accurate estimate of the effective elastic properties, in particular for a case where the composite has components with widely different values of the elastic constants. For comparison we have discussed the results based on Kröner's theory which also purports to solve the same problem. It is found that the two solutions do not agree. To resolve the difference we take help of Hill's exact solution of the composite problem when the components have equal rigidities. It is found that while Kröner's theory is inconsistent with the exact result the present self-consistent solution analytically reproduces it. Another interesting finding of the present investigation is that the approximations made in obtaining the self-consistent solution are exact in the limit of composites with equal-shear moduli. Finally it is indicated that although the results for composites have been derived for isotropic and cubic components it can be easily adapted for a composite with noncubic components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.336032
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  • 10
    Electronic Resource
    Electronic Resource
    A Green's function approach to third-order elastic constants of disordered solids (1986)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 27 (1986), S. 2807-2812 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Starting from a Lippmann–Schwinger-type equation, which is very similar to that of quantum mechanical multiple scattering theory, Zeller and Dederichs [Phys. Status Solidi B 55, 831 (1973)] have developed the effective medium theory. This theory has found wide application in understanding the mechanical behavior of disordered solids. However, unlike the problem in quantum mechanics, this equation of the random elasticity is only approximate since this is a linear response theory. So, it is proposed in this work for the first time to go beyond this approximation to treat nonlinear properties of such solids of which the third-order elastic constant is a generic. Again, so far as the nonlinear elastic behavior of these solids is concerned, no work has been done except the simple Voigt- and Reuss-type averaging. Both are extreme approximations and are, moreover, known to lead to violation of the equilibrium condition. The salient feature of the present calculation is to get an exact formal solution of the problem in terms of an appropriate Green's function in a closed form. The result obtained is quite general and may be adopted to treat nonlinearity in any tensor property of disordered materials. Finally several approximations, including a self-consistent solution, have been discussed for obtaining the effective nonlinear static mechanical susceptibility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527256
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