Abstract
Hard mode Raman spectroscopy (HMRS) on hypersolvus alkali feldspar shows a temperature dependence of the order parameter of the displacive\({{C2} \mathord{\left/ {\vphantom {{C2} {m{\text{ - }}C\bar 1}}} \right. \kern-\nulldelimiterspace} {m{\text{ - }}C\bar 1}}\) phase transition following mean-field behaviour:
At lower temperatures, a spontaneous saturation sets in, which is attributed to site-ordering effects of the alkali atoms even in hypersolvus anorthoclase. Fluctuational line broadening of Si-O viration bands is explained by strong lattice distortions around alkali positions and local deformation of the Al,Si,O network. The thermodynamic relevance of these distortions is discussed in relation to the possibility of an additional diffuse phase transition occurring atT d =302 K. The experimental results of HMRS are compared with those on Al,Si ordered and disordered albite, where no fluctuation broadening occurs.
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Bismayer U, Salje E, Glazer AM, Cosier J (1986) Effect of strain induced order parameter coupling on the ferroelastic behaviour in lead phosphate-arsenate. Phase Transitions 6:126–151
Brown GE, Fenn PM (1979) Structure energies of the alkali feldspars. Phys Chem Minerals 4:83–100
Bruce AD, Taylor W, Murray AF (1980) Precursor order and Raman scattering near displacive phase transitions. J Phys C 13:483–504
Burnham CW (1985) Mineral structure energetics and modelling using the ionic approach. Rev Mineral 14:347–386
Burns G, Dacol FH (1983) Glassy polarization behaviour in ferroelectric compounds Pb(Mg1/3 Nb2/3) O3 and Pb(Zn1/3 Nb2/3) O3. Solid State Commun 48:853–856
Fenn PM, Brown GE (1977) Crystal structure of a synthetic, compositionally intermediate, hypersolvus alkali feldspar: evidence for Na,K site ordering. Z Kristallogr 145:124–145
Ghose S, Salje E (1986) Correlation between thermal ellipsoids and Lattice vibrations in Na-feldspar. In preparation
Grundy HP, Brown WL (1969) A high-temperature X-ray study of the equilibrium forms of albite. Mineral Mag 37 No 286:156–172
Imry Y (1975) On the statistical mechanics of coupled order parameters. J Phys C 8:567–577
Kroll H, Schmiemann I, V Cölln G (1986) Feldspar solid solutions. Am Mineral 71:1–16
Salje E (1985) Thermodynamics of sodium feldspar I: order parameter treatment and strain induced coupling effects. Phys Chem Minerals 12:93–98
Salje E (1986) Raman spectroscopy in fractal materials. In preparation
Salje E, Devarajan V (1986) Phase transitions in systems with strain induced coupling between two order parameters. Phase Transitions 6:235–247
Salje E, Wruck B (1983) Specific-heat measurements and critical exponents of the ferroelastic phase transition in Pb3(PO4)2 and Pb3(P1−xAsO4)2. Phys Rev B28:6510–6518
Salje E, Devarajan V, Bismayer U, Guimaraes DMC (1983) Phase transitions in Pb3(P1−xAsxO4)2; influence of the central peak and flip mode on the Raman scattering of hard modes. J Phys C 16:5233–5243
Salje E, Kuscholke B, Wruck B, Kroll H (1985a) Thermodynamics of sodium feldspar II: experimental results and numerical calculations. Phys Chem Minerals 12:99–107
Salje E, Kuscholke B, Wruck B (1985b) Domain wall formation in minerals: I Theory of twin boundary shapes in Na-feldspar. Phys Chem Minerals 12:132–140
Strob WD (1983) Strukturverfeinerung eines Tief Mikroclins. Inaugural Dissertation Münster
Winterfeld V, Schaak G (1977) Phonon contributions to the anomalous specific heat of triglycine sulphate near T c . Phys Status Solidi B80:559–567
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Salje, E. Raman spectroscopic investigation of the order parameter behaviour in hypersolvus alkali feldspar: Displacive phase transition and evidence for Na-K site ordering. Phys Chem Minerals 13, 340–346 (1986). https://doi.org/10.1007/BF00308352
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DOI: https://doi.org/10.1007/BF00308352