Ronald Miletich

Bio: Ronald Miletich is an academic researcher from University of Vienna. The author has contributed to research in topics: Phase transition & Crystal structure. The author has an hindex of 16, co-authored 61 publications receiving 1268 citations. Previous affiliations of Ronald Miletich include University of Bayreuth & ETH Zurich.

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

Abstract: The unit-cell parameters of quartz, SiO2, have been determined by single-crystal diffraction at 22 pressures to a maximum pressure of 8.9 GPa (at room temperature) with an average precision of 1 part in 9000. Pressure was determined by the measurement of the unit-cell volume of CaF2 fluorite included in the diamond-anvil pressure cell. The variation of quartz unit-cell parameters with pressure is described by: a −4.91300 (11) = −0.0468 (2) P + 0.00256 (7) P2 − 0.000094 (6) P3, c − 5.40482 (17) = − 0.03851 (2) P + 0.00305 (7) P2 − 0.000121 (6) P3, where P is in GPa and the cell parameters are in angstroms. The volume–pressure data of quartz are described by a Birch–Murnaghan third-order equation of state with parameters V0 = 112.981 (2) a3, KT0 = 37.12 (9) GPa and K′ = 5.99 (4). Refinement of K′′ in a fourth-order equation of state yielded a value not significantly different from the value implied by the third-order equation. The use of oriented quartz single crystals is proposed as an improved internal pressure standard for high-pressure single-crystal diffraction experiments in diamond-anvil cells. A measurement precision of 1 part in 10 000 in the volume of quartz leads to a precision in pressure measurement of 0.009 GPa at 9 GPa.

High-Pressure Single-Crystal Techniques

Abstract: The development of apparatus to maintain materials at high hydrostatic pressure has been an active area of research for many years. From the pioneering work of Bridgman, during the early part of this century (Bridgman 1971), until the late 1960s, massive hydraulicly driven Bridgman-anvil and piston-cylinder devices dominated high-pressure science. Although there were later improvements in design, such as multi-anvil devices, it was not until the advent of the gasketed diamond-anvil cell, in the mid 1960s, that high-pressure studies were possible in non-specialized laboratories. Diamond has remarkable properties; not only is it the hardest known material it is also highly transparent to many ranges of electromagnetic radiation. Indeed incorporating these attributes, the gasketed diamond-anvil cell has become the standard tool for the generation of high pressures over the last three decades and has been applied in a wide range of experimental studies such as Brillouin scattering (Whitfield et al. 1976), Raman spectroscopy (Sharma 1977, Sherman 1984), NMR measurements (Lee et al. 1987) and, of course X-ray diffraction. It is this utility across a large range of science through physics, earth science and lately the life sciences that makes the development of the diamond-anvil cell as significant a revolution for measurement under non-ambient conditions in the physical sciences as that of the invention of the transistor to the whole sphere of electronics and computation. Figure 1. Assembly of the gasketed diamond-anvil cell: principle of pressure generation. As with all successful designs, the principles upon which the gasketed diamond-anvil cell (Van Valkenburg 1964) operates are elegantly simple (Fig. 1). The sample is placed in a pressure chamber created between the flat parallel faces (culets) of two opposed diamond anvils and the hole penetrating a hardened metal foil (= the gasket). A pressure calibrant is placed beside the sample and the free volume within …

A diamond-anvil cell for single-crystal x-ray diffraction studies to pressures in excess of 10 GPa

Abstract: A new diamond‐anvil cell for single‐crystal x‐ray diffraction structural studies is presented. By including a simple mechanism for adjusting the parallelism of the opposing diamond culets, the stability of the gasket is maintained to higher pressures than was achieved in earlier cells of a similar two‐platen design. Equipped with 600 μm culet diamond anvils, the cell has been tested to a pressure of 25 GPa and has been used successfully for equation‐of‐state measurements and crystal structure determinations to 10 GPa.

Compressibility and thermal expansivity of synthetic apatites, Ca 5 (PO 4 ) 3 X with X = OH, F and Cl

Abstract: The room-temperature unit-cell volumes of synthetic hydroxylapatite, Ca 5 (PO 4 ) 3 OH, fluorapatite, Ca 5 (PO 4 ) 3 (F (sub 1-x) ,OH x ) with x = 0.025, and chlorapatite, Ca 5 (PO 4 ) 3 (Cl (sub 0.7) ,OH (sub 0.3) ), have been measured by high-pressure (diamond anvil-cells) synchrotron X-ray powder diffraction to maximum pressures of 19.9 GPa, 18.3 GPa, and 51.9 GPa, respectively. Fits of the data with a second-order Birch-Murnaghan EOS (i.e. (dK/dP) (sub P = O) = 4) yield bulk moduli of Ko = 97.5 (1.8) GPa, K 0 = 97.9 (1.9) GPa and K 0 = 93.1(4.2) GPa, respectively. The room-pressure volume variation with temperature was measured on the same hydroxyl- and fluorapatite synthetic samples using a Huber Guinier camera up to 962 and 907 degrees C, respectively. For hydroxyl- and fluorapatite, the volume data were fitted to a second-order polynomial: V(T)/V 293 = 1+alpha 1 (T-293)+alpha 2 (T-293) 2 with T expressed in K leading to alpha 1 OH = 2.4(+ or -0.1)X10 (super -5) K (super -1) , alpha 2 OH = 2.7(+ or -0.1)X10 (super -8) K (super -2) and alpha 1 F = 3.4(+ or -0.1)X10 (super -5) K (super -1) , alpha 2 F = 1.6(+ or -0.1)X10 (super -8) K (super -2) , respectively. A significant increase is observed in hydroxyl-apatite thermal expansion above ca. 550 degrees C and extra reflections start to clearly appear on the X-ray film above 790 degrees C. These features are interpreted as the progressive dehydration of slightly Ca-deficient hydroxylapatite (i.e. with Ca/P 2 , hydroxylapatite should dehydrate to form gamma -Ca 3 (PO 4 ) 2 +Ca 3 Al 2 Si 3 O 12 below 12 GPa, i.e. below the upper-pressure stability-limit of apatite that was previously determined experimentally.

A simple and generalised P–T–V EoS for continuous phase transitions, implemented in EosFit and applied to quartz

Abstract: Continuous phase transitions in minerals, such as the α–β transition in quartz, can give rise to very large non-linear variations in their volume and density with temperature and pressure. The extension of the Landau model in a fully self-consistent form to characterize the effects of pressure on phase transitions is challenging because of non-linear elasticity and associated finite strains, and the expected variation of coupling terms with pressure. Further difficulties arise because of the need to integrate the resulting elastic terms over pressure to achieve a description of the P–T–V equation of state. We present a fully self-consistent simplified description of the equation of state of minerals with continuous phase transitions based on a purely phenomenological adaptation of Landau theory. The resulting P–T–V EoS includes the description of the elastic softening occurring in both phases with the minimum number of parameters. By coupling the volume and elastic behaviour of the mineral, this approach allows the EoS parameters to be determined by using both volume and elastic data, and avoids the need to use data at simultaneous P and T. The transition model has been incorporated in to the EosFit7c program, which allows the parameters to be determined by simultaneous fitting of both volume and elastic data, and all types of equation of state calculations to be performed. Quartz is used as an example, and the parameters to describe the full P–T–V EoS of both α- and β-quartz are determined.

Compositions of the Apatite-Group Minerals: Substitution Mechanisms and Controlling Factors

Abstract: The apatite-group minerals of the general formula, M10(ZO4)6X2 (M = Ca, Sr, Pb, Na…, Z = P, As, Si, V…, and X = F, OH, Cl…), are remarkably tolerant to structural distortion and chemical substitution, and consequently are extremely diverse in composition (e.g., Kreidler and Hummel 1970; McConnell 1973; Roy et al. 1978; Elliott 1994). Of particular interest is that a number of important geological, environmental/paleoenvironmental, and technological applications of the apatite-group minerals are directly linked to their chemical compositions. It is therefore fundamentally important to understand the substitution mechanisms and other intrinsic and external factors that control the compositional variation in apatites. The minerals of the apatite group are listed in Table 1⇓, and representative compositions of selected apatite-group minerals are given in Table 2⇓. Also, more than 100 compounds with the apatite structure have been synthesized (Table 3⇓). Phosphate apatites, particularly fluorapatite and hydroxylapatite, are by far the most common in nature and are often synonymous with “apatite(s)”. For example, fluorapatite is a ubiquitous accessory phase in igneous, metamorphic, and sedimentary rocks and a major constituent in phosphorites and certain carbonatites and anorthosites (McConnell 1973; Dymek and Owens 2001). Of particular importance in biological systems, hydroxylapatite and fluorapatite (and their carbonate-bearing varieties) are important mineral components of bones, teeth and fossils (McConnell 1973; Wright et al. 1984; Grandjean-Lecuyer et al. 1993; Elliott 1994; Wilson et al. 1999; Suetsugu et al. 2000; Ivanova et al. 2001). View this table: Table 1. Summary of the apatite-group minerals View this table: Table 2. Representative compositions and unit-cell parameters of selected apatite-group minerals. View this table: Table 3. Formulas of selected synthetic compounds with the apatite structure. Following Fleischer and Mandarino (1995), Table 1⇑ also includes melanocerite-(Ce), tritomite-(Ce), and tritomite-(Y), the compositions …

Equations of State

Abstract: Diffraction experiments at high pressures provide measurement of the variation of the unit-cell parameters of the sample with pressure and thereby the variation of its volume (or equivalently its density) with pressure, and sometimes temperature. This last is known as the ‘Equation of State’ (EoS) of the material. It is the aim of this chapter to present a detailed guide to the methods by which the parameters of EoS can be obtained from experimental compression data, and the diagnostic tools by which the quality of the results can be assessed. The chapter concludes with a presentation of a method by which the uncertainties in EoS parameters can be predicted from the uncertainties in the measurements of pressure and temperature, thus allowing high-pressure diffraction experiments to be designed in advance to yield the required precision in results. The variation of the volume of a solid with pressure is characterised by the bulk modulus, defined as K = − V ∂ P /∂ V . Measured equations of state are usually parameterized in terms of the values of the bulk modulus and its pressure derivatives, K′ = −∂ K /∂ P and K″ = −∂2 K /∂ P 2, evaluated at zero pressure. These zero-pressure (or, almost equivalent, the room-pressure values) are normally denoted by a subscript “0,” thus: K = − V (∂ P /∂ V ) P =0, K ′ = −(∂ K /∂ P ) P =0, and K ″ = −(∂2 K /∂ P 2) P =0. However, throughout this chapter a number of notational conventions are followed for ease of presentation. Unless specifically stated, the symbols K′ and K ″ (without subscript) refer to the zero-pressure values at ambient temperature, all references to bulk modulus, K …

Effective hydrostatic limits of pressure media for high-pressure crystallographic studies

Abstract: The behavior of a number of commonly used pressure media, including nitrogen, argon, 2-propanol, a 4:1 methanol–ethanol mixture, glycerol and various grades of silicone oil, has been examined by measuring the X-ray diffraction maxima from quartz single crystals loaded in a diamond-anvil cell with each of these pressure media in turn. In all cases, the onset of non-hydrostatic stresses within the medium is detectable as the broadening of the rocking curves of X-ray diffraction peaks from the single crystals. The onset of broadening of the rocking curves of quartz is detected at ∼9.8 GPa in a 4:1 mixture of methanol and ethanol and at ∼4.2 GPa in 2-propanol, essentially at the same pressures as the previously reported hydrostatic limits determined by other techniques. Gigahertz ultrasonic interferometry was also used to detect the onset of the glass transition in 4:1 methanol–ethanol and 16:3:1 methanol–ethanol–water, which were observed to support shear waves above ∼9.2 and ∼10.5 GPa, respectively, at 0.8–1.2 GHz. By contrast, peak broadening is first detected at ∼3 GPa in nitrogen, ∼1.9 GPa in argon, ∼1.4 GPa in glycerol and ∼0.9 GPa in various grades of silicone oil. These pressures, which are significantly lower than hydrostatic limits quoted in the literature, should be considered as the practical maximum limits to the hydrostatic behavior of these pressure media at room temperature.

A wide-ranging review on Nasicon type materials

Abstract: Nasicons (sodium super ion conductors) are a class of solid electrolytes. Their structure, compositional diversity, evolution, and applications are reviewed. A wide range of materials is considered based on crystalline and glassy Nasicon compositions.