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1.
We obtained 503 photographic brightness estimates for the long-period classical Cepheid V396 Cyg (P = 33.3 days) from the plates of the Harvard Observatory and the Sternberg Astronomical Institute (SAI). Combined with published photoelectric observations, these data were used to plot an O-C diagram covering a time interval of 108 years. The O-C diagram is parabolic in shape, enabling the first determination of quadratic light elements and calculation of the evolutionary rate of decrease of the period, dP/dt = 14.1(±0.8) s per year (log(?/P) = ?6.35), in agreement with theoretical computations for the second crossing of the instability strip. The available data, reduced using the method introduced by Eddington and Plakidis, demonstrate the presence of small random period fluctuations that do not distort the evolutionary changes of the O-C residuals. 相似文献
2.
Photographic plates of the Harvard Observatory stacks have been used to obtain 1261 brightness estimates for the low-amplitude Cepheid FF Aql (P = 4.47 days). Combined with published visual, photoelectric, and CCD observations, these data enable the construction of an O-C diagram spanning 122 years. The resulting O-C diagram is parabola-shaped, enabling the determination of quadratic brightness elements for the first time. The evolutionary rate of increase of the period, dP/dt = 0.072 ± 0.011 s/year, is in agreement with theoretical computations for the third crossing of the instability strip. The available data, reduced using the technique of by Eddington and Plakidis, reveal the presence of small, random period fluctuations, ? = 0.0061d ± 0.0044d, that do not distort the evolutionary trend of the O-C residuals. 相似文献
3.
I. F. Malov 《Astronomy Reports》2010,54(10):925-931
The latest observational data are analyzed to investigate their consistency with two known models for anomalous X-ray pulsars
(AXPs) and soft gamma-ray repeaters (SGRs): the magnetar and drift models. The results of spectral measurements disagree with
the predictions of theories that assume the presence of super-strong magnetic fields on AXPs and SGRs and associated processes
for the generation of electron-positron plasma in the upper layers of the neutron-star magnetosphere. We present arguments
against the use of magnetic-dipole braking for these objects. The rotational periods P, period derivatives dP/dt, and magnetic fields B of known AXPs and SGRs are calculated for the drift model. The mean values of these parameters in the sample used are 〈P〉 = 108 ms and 〈log B
s
[G]〉 = 12.08. Overall, the measured profiles, polarizations, and spectra can be brought into agreement with the drift model. 相似文献
4.
We present the first estimates of the relative and absolute parameters of the eclipsing binary EQ Boo based on a light-curve
analysis (P = 5.43d, V = 8.8
m
). This star is simultaneously Component A of the visual binary ADS 9422 (spectral types F7V + G0V; separation of the components
1.3″; magnitude difference 0.7
m
). The derived disagreement between the components’ physical parameters and the assumption that they have the same age can
be removed if there is a fourth, late-type star in the system. This is also able to explain the observed anomaly in the behavior
of the O-C residuals at times of minima. 相似文献
5.
Data on the profiles and polarization of the 10- and 20-cm emission of radio pulsars are used to calculate the angle β between the rotational axis of the neutron star and its magnetic moment. It is shown that, for these calculations, it is
sufficient to use catalog values of the pulse width at the 10% level W
10, since the broadening of the observed pulses due to the transition to the full width W
0 and narrowing of the pulses associated with the emission of radiation along tangents to the field lines approximately cancel
each other out. The angles β
1 are calculated for 283 pulsars at 20 cm and 132 pulsars at 10 cm, assuming that the line of sight passes through the center
of the emission cone. The mean values of these angles are small and similar for the two wavelengths (〈β
1〉 = 18° at λ = 10 cm and 〈β
1〉 = 14° at λ = 20 cm). The angle β
2 is estimated for several dozen pulsars for the case when the orientation of the angle to the line of sight is arbitrary.
The mean value of β
2 at 10 cm is found to be 〈β
2〉 = 33.9° if the maximum derivative of the polarization position angle C is positive and 〈β
2〉 = 52.1° ifC < 0. We find at 20 cm 〈β
2〉 = 33.9° ifC > 0 and 〈β2〉 = 54.1° ifC < 0. The values at the two wavelengths are equal within the errors, and close to the β
2 value obtained earlier at 30 cm (〈β
2〉 = 36.4° if C >0 and 〈β2〉 = 49.1° if C < 0). The mean 〈β
2〉 for the entire set of data can be taken to be 43.5°. The period dependence of the pulse width W(P) √ P
−0.25 differs from the relation that is usually used in the polar-cap model, W(P) √ P
−0.5. This difference could be associated with the rate of development of plasma instabilities near the surface of the neutron
star (in the region where high-frequency radiation is generated). The role of the quadrupole component of the magnetic field
is not important here. There is no dependence of the angle β on the pulsar age (z distance, luminosity L, or characteristic age τ = P/(2dP/dt)) for the studied sample. 相似文献
6.
During the analysis of archived VLF data from Indian low latitude ground stations, some discrete VLF emissions recorded at
the low latitude ground station Gulmarg (geomagnetic latitude 24°26′N; geomagnetic longitude 147°09′E, L = 1.28) during moderate
magnetic storm activity (Σ K
P
− = 32, K
P
index varies from 4 to 6 during the observation period) on 6/7 March, 1986 are presented in this paper. The dynamic spectra
of these discrete VLF emissions were observed along with tweeks and its harmonics, which is interesting and complex to explain.
In most of the events the harmonic frequency of tweeks correlates with the starting frequency of harmonics of discrete emissions.
In order to explain the observed features of discrete VLF emissions, we propose cyclotron resonance interaction between whistler
mode wave and energetic electrons of inner radiation belt as possible generation mechanism. An attempt is also made to determine
parallel energy, anisotropy and wave growth relevant to the generation process of VLF emissions. 相似文献
7.
P. Comodi G. D. Gatta P. F. Zanazzi D. Levy W. Crichton 《Physics and Chemistry of Minerals》2002,29(8):538-544
Powder diffraction measurements at simultaneous high pressure and temperature on samples of 2M1 polytype of muscovite (Ms) and paragonite (Pg) were performed at the beamline ID30 of ESRF (Grenoble), using the Paris-Edinburgh
cell. The bulk moduli of Ms, calculated from the least-squares fitting of V–P data on each isotherm using a second-order Birch–Murnaghan EoS, were: 57.0(6), 55.1(7), 51.1(7) and 48.9(5) GPa on the isotherms
at 298, 573, 723 and 873 K, respectively. The value of (∂K
T
/∂T)
was −0.0146(2) GPa K−1. The thermal expansion coefficient α varied from 35.7(3) × 10−6 K−1 at P ambient to 20.1(3) × 10−6 K−1 at P = 4 GPa [(∂α/∂P)
T
= −3.9(1) × 10−6 GPa−1 K−1]. The corresponding values for Pg on the isotherms at 298, 723 and 823 K were: bulk moduli 59.9(5), 55.7(6) and 53.8(7) GPa,
(∂K
T
/∂T)
−0.0109(1) GPa K−1. The thermal expansion coefficient α varied from 44.1(2) × 10−6 K−1 at P ambient to 32.5(2) × 10−6 K−1 at P = 4 GPa [(∂α/∂P)
T
= −2.9(1) × 10−6 GPa−1 K−1]. Thermoelastic coefficients showed that Pg is stiffer than Ms; Ms softens more rapidly than Pg upon heating; thermal expansion
is greater and its variation with pressure is smaller in Pg than in Ms.
Received: 28 January 2002 / Accepted: 5 April 2002 相似文献
8.
Summary High-grade blocks in the Franciscan complex at Tiburon, California, record relatively low temperature eclogite-facies metamorphism
and blueschist-facies overprinting. The eclogite-facies mineral assemblage contains prograde-zoned garnet + omphacite + epidote
± hornblende (katophoritic and barroisitic Ca–Na amphibole) ± glaucophane + phengite (∼3.5 Si p.f.u.) ± paragonite + rutile
+ quartz. The blueschist-facies mineral assemblage contains chlorite + titanite + glaucophane + epidote ± albite ± phengite
(∼3.3 Si p.f.u.). Albite is not stable in the eclogite stage. New calculations based on garnet-omphacite-phengite thermobarometry
and THERMOCALC average-P–T calculations yield peak eclogite-facies P–T conditions of P = 2.2–2.5 GPa and T = 550–620 °C; porphyroclastic omphacite with inclusions of garnet and paragonite yields an average-P–T of 1.8 ± 0.2 GPa at 490 ± 70 °C for the pre-peak stage. The inferred counterclockwise hairpin P–T trajectory suggests prograde eclogitization of a relatively “cold” subducting slab, and subsequent exhumation and blueschist-facies
recrystallization by a decreasing geotherm. Although an epidote-garnet amphibolitic assemblage is ubiquitous in some blocks,
P–T pseudosection analyses imply that the epidote-garnet amphibolitic assemblage is stable during prograde eclogite-facies metamorphism.
Available geochronologic data combined with our new insight for the maximum pressure suggest an average exhumation rate of
∼5 km/Ma, as rapid as those of some ultrahigh pressure metamorphic terranes. 相似文献
9.
Elastic wave velocities for dense (99.8% of theoretical density) isotropic polycrystalline specimens of synthetic pyrope (Mg3Al2Si3O12) were measured to 1,000 K at 300 MPa by the phase comparison method of ultrasonic interferometry in an internally heated
gas-medium apparatus. The temperature derivatives of the elastic moduli [(∂Ks/∂T)
P
= −19.3(4); (∂G/∂T)
P
= −10.4(2) MPa K−1] measured in this study are consistent with previous acoustic measurements on both synthetic polycrystalline pyrope in a
DIA-type cubic anvil apparatus (Gwanmesia et al. in Phys Earth Planet Inter 155:179–190, 2006) and on a natural single crystal by the rectangular parallelepiped resonance (RPR; Suzuki and Anderson in J Phys Earth 31:125–138,
1983) method but |(∂Ks/∂T)
P
| is significantly larger than from a Brillouin spectroscopy study of single-crystal pyrope (Sinogeikin and Bass in Phys Earth
Planet Inter 203:549–555, 2002). Alternative approaches to the retrieval of mixed derivatives of the elastic moduli from joint analysis of data from this
study and from the solid-medium data of Gwanmesia et al. in Phys Earth Planet Inter 155:179–190 (2006) yield ∂2
G/∂P∂T = [0.07(12), 0.20(14)] × 10−3 K−1 and ∂2
K
S
/∂P∂T = [−0.20(24), 0.22(26)] × 10−3 K−1, both of order 10−4 K−1 and not significantly different from zero. More robust inference of the mixed derivatives will require solid-medium acoustic
measurements of precision significantly better than 1%. 相似文献
10.
Y. Vapnik V. V. Sharygin V. Samoilov Z. Yudalevich 《International Journal of Earth Sciences》2007,96(4):663-684
The basic and ultrabasic alkaline rocks of western Makhtesh Ramon, Israel crop out in numerous lava flows and subvolcanic
bodies. The rock suite is composed of tephrite, basanite, basanitic nephelinite, analcimite, olivine nephelinite, and melilite-olivine
nephelinite and in many outcrops is represented by glass-bearing varieties. Melt and fluid inclusions have been studied in
olivine, clinopyroxene, and plagioclase phenocrysts. The EP, SIMS and microthermometry methods were used for inclusion study.
The geochemical data obtained on glasses of melt inclusions (major, REE, trace elements, volatiles) are compared with the
data on whole-rock and groundmass glass compositions. The compositions of melt inclusions reflect the different stages of
rock crystallization: the initial products of crystallization are similar to whole-rock compositions whereas final portions
of melts are usually enriched in SiO2, Al2O3, and alkalis, and depleted in mafic components. The data on contemporaneous melt and CO2 inclusions were used for the evaluation of the P–T conditions of rock generation. The following parameters were obtained: tephrite: P = 6.3–7.7 kbar and T = 1,150–1,250°C; basanite: P = 6.6–9.2 kbar and T = 1,150–1,250°C; olivine and analcime-olivine nephelinite: P = 5.6–8.2 kbar and T = 1,150–1,250°C; melilite-olivine nephelinite: 4.0–5.4 kbar and T mainly between 1,150 and 1,200°C. Magma genesis was restricted to P–T conditions of spinel- and plagioclase-lherzolite fields. These data suggest the shallowest depth of magma genesis occurred
in Makhtesh Ramon compared to other occurrences of Early Cretaceous magmatism at the Middle East. Differences in the degree
of batch partial melting of the same source rocks best explain the diversity of the igneous suite in western Makhtesh Ramon. 相似文献
11.
The accepted standard state entropy of titanite (sphene) has been questioned in several recent studies, which suggested a
revision from the literature value 129.3 ± 0.8 J/mol K to values in the range of 110–120 J/mol K. The heat capacity of titanite
was therefore re-measured with a PPMS in the range 5 to 300 K and the standard entropy of titanite was calculated as 127.2
± 0.2 J/mol K, much closer to the original data than the suggested revisions. Volume parameters for a modified Murgnahan equation
of state: V
P,T
= V
298° × [1 + a°(T − 298) − 20a°(T − 298)] × [1 – 4P/(K
298 × (1 – 1.5 × 10−4 [T − 298]) + 4P)]1/4 were fit to recent unit cell determinations at elevated pressures and temperatures, yielding the constants V
298° = 5.568 J/bar, a° = 3.1 × 10−5 K−1, and K = 1,100 kbar. The standard Gibbs free energy of formation of titanite, −2456.2 kJ/mol (∆H°f = −2598.4 kJ/mol) was calculated from the new entropy and volume data combined with data from experimental reversals on the
reaction, titanite + kyanite = anorthite + rutile. This value is 4–11 kJ/mol less negative than that obtained from experimental
determinations of the enthalpy of formation, and it is slightly more negative than values given in internally consistent databases.
The displacement of most calculated phase equilibria involving titanite is not large except for reactions with small ∆S. Re-calculated baric estimates for several metamorphic suites yield pressure differences on the order of 2 kbar in eclogites
and 10 kbar for ultra-high pressure titanite-bearing assemblages. 相似文献
12.
Detlef W. Fasshauer Bernd Wunder Niranjan D. Chatterjee Günther W. H. Höhne 《Contributions to Mineralogy and Petrology》1998,131(2-3):210-218
The heat capacity of synthetic, stoichiometric wadeite-type K2Si4O9 has been measured by DSC in the 195≤T(K)≤598 range. Near the upper temperature limit of our data, the heat capacity observed by DSC agrees with that reported by
Geisinger et al. (1987) based on a vibrational model of their infrared and Raman spectroscopic data. However, with decreasing
temperature, the Cp observed by DSC is progressively higher than that predicted from the vibrational model, suggesting that
the standard entropy of K2Si4O9 is likely to be larger than 198.9 ± 4.0 J/K · mol computed from the spectroscopic data. A fit to the DSC data gave: Cp(T) = 499.13 (±1.87) − 4.35014 · 103(±3.489 · 101) · T
−0.5, with T in K and average absolute percent deviation of 0.37%. The room-temperature compressibilities of kalsilite and leucite, hitherto
unknown, have been measured as well. The data, fitted to the Murnaghan equation of state, gave K
o = 58.6 GPa, K
o
′ = 0.1 for kalsilite and K
o = 45 GPa, K
o
′ = 5.7 for α-leucite. Apart from the above mentioned data on the properties of the individual phases, we have also obtained
reaction-reversals on four equilibria in the system K2O-Al2O3-SiO2. The Bayesian method has been used simultaneously to process the properties of 13 phases and 15 reactions between them to
derive an internally consistent thermodynamic dataset for the K2O-Al2O3-SiO2 ternary. The enthalpy of formation of K2Si4O9 wadeite is in perfect agreement with its revised calorimetric value, the standard entropy is 232.1 ± 10.4 J/K · mol, ∼15%
higher than that implied by vibrational modeling. The phase diagram, generated from our internally consistent thermodynamic
dataset, shows that for all probable P-T trajectories in the subduction regime, the stable pressure-induced decomposition of K-feldspar will produce coesite + kalsilite rather than coesite + kyanite + K2Si4O9 (cf. Urakawa et al. 1994).
Received: 11 June 1997 / Accepted: 2 December 1997 相似文献
13.
A. Pavese 《Physics and Chemistry of Minerals》2002,29(1):43-51
The P–V–T equation of state (EoS) models of Birch–Murnaghan, Vinet and Poirier–Tarantola have been compared with one another and discussed
in the light of their ability to reproduce thermoelastic functions and parameters by means of fitting to pressure–volume–temperature
data artificially generated for spinel, corundum and forsterite. Numerical simulations relying upon semi-empirical potentials,
lattice dynamics and the quasiharmonic approximation have been used to generate P–V–T data. The results obtained indicate that all the P–V–T EoSs tested predict bulk modulus at ambient conditions with errors confined, at worst, within a few percent, and reproduce
correctly its dependence on temperature. The derivatives of the bulk modulus versus P and PT are less satisfactorily modelled. The bulk thermal expansion is determined by EoSs within a few percent error, but the deviations
increase significantly if the approximation of linear dependence of EoS on temperature is used (linearised thermal pressure
model).
Received: 30 January 2001 / Accepted: 16 June 2001 相似文献
14.
Sytle M. Antao Ian Jackson Baosheng Li Jennifer Kung Jiuhua Chen Ishmael Hassan Robert C. Liebermann John B. Parise 《Physics and Chemistry of Minerals》2007,34(5):345-350
The elastic moduli of magnesioferrite spinel, MgFe2O4, and their temperature dependence have been determined for the first time by ultrasonic measurements on a polycrystalline
specimen. The measurements were carried out at 300 MPa and to 700°C in a gas-medium high-pressure apparatus. On heating, both
the elastic bulk (K
S) and shear (G) moduli decrease linearly to 350°C. By combining with extant thermal-expansion data, the values for the room-temperature
K
S and G, and their temperature derivatives are as follows: K
0 = 176.3(7) GPa, G
0 = 80.1(2) GPa, (∂K
S/∂T)
P
= −0.032(3) GPa K−1 and (∂G/∂T)
P
= −0.012(1) GPa K−1. Between 350 and 400°C, there are abrupt increases of 1.4% in both of the elastic moduli; these closely coincide with the
magnetic Curie transition that was observed by thermal analyses at about 360°C. 相似文献
15.
M. V. Kuznetsov Kh. F. Khaliullin A. I. Khaliullina V. G. Metlov L. V. Mossakovskaya 《Astronomy Reports》2011,55(11):989-999
We have derived the first photoelectric light curve of the eclipsing binary V974 Cyg from our own photoelectric observations.
Analysis of the light curve has yielded the system’s photometric elements (r
1 ≈ r
2 = 0.1192, e = 0.058, L
1 ≈ L
2 = 0.486, and L
3 = 0.028) and absolute parameters (M
1 ≈ M
2 = 2.2M
⊙, T
eff,1 ≈ T
eff,2 = 9500 K, a = 15.0R
⊙, distance d = 1.29 kpc, age log t = 8.0, t/tMS = 0.11). We have detected apsidal motion with the period U
obs
= (1140 ± 170) yrs, and the presence of a third body in the system. The orbital parameters derived for the third body are
P
3 = 26.5 yrs, e
3 = 0.78, and a
3 sin i
3 = 1.5 AU; and the lower limit for its mass is M
3 > 0.58M
⊙. The observed apsidal-motion rate is higher than is expected theoretically by a factor of 1.5. The axial rotation of the
system’s components is not yet synchronized with the orbital motion, probably because V974 Cyg is relatively young and detached. 相似文献
16.
P. B. Tomascak Eirik J. Krogstad Richard J. Walker 《Contributions to Mineralogy and Petrology》1996,125(1):45-59
Neodymium and lead isotope and elemental data are presented for the Sebago batholith (293±2 Ma), the largest exposed granite
in New England. The batholith is lithologically homogeneous, yet internally heterogeneous with respect to rare earth elements
(REE) and Nd isotopic composition. Two-mica granites in the southern/central portion of the batholith (group 1) are characterized
by REE patterns with uniform shapes [CeN/YbN (chondrite normalized) = 9.4–19 and Eu/Eu* (Eu anomaly) = 0.27–0.42] and ɛ
Nd(t) = −3.1 to −2.1. Peripheral two-mica granites (group 2), spatially associated with stromatic and schlieric migmatites,
have a wider range of total REE contents and patterns with variable shapes (CeN/YbN = 6.1–67, Eu/Eu* = 0.20–0.46) and ɛ
Nd(t) = −5.6 to −2.8. The heterogeneous REE character of the group 2 granites records the effects of magmatic differentiation
that involved monazite. Coarse-grained leucogranites and aplites have kinked REE patterns and low total REE, but have Nd isotope
systematics similar to group 2 granites with ɛ
Nd(t) = −5.5 to −4.7. Rare biotite granites have steep REE patterns (CeN/YbN = 51–61, Eu/Eu* = 0.32–0.84) and ɛ
Nd(t) = −4.6 to −3.8. The two-mica granites have a restricted range in initial Pb isotopic composition (206Pb/204Pb = 18.41–18.75; 207Pb/204Pb = 15.60–15.68; 208Pb/204Pb = 38.21–38.55), requiring and old, high U/Pb (but not Th/U) source component. The Nd isotope data are consistent with magma
derivation from two sources: Avalon-like crust (ɛ
Nd>−3), and Central Maine Belt metasedimentary rocks (ɛ
Nd<−4), without material input from the mantle. The variations in isotope systematics and REE patterns are inconsistent with
models of disequilibrium melting which involved monazite.
Received: 8 December 1995 / Accepted: 29 April 1996 相似文献
17.
The detection of pulsed radio emission from the X-ray pulsar AXP 4U 0142+61 with a period of P = 8.68832935(6) s and a period derivative of $
\dot P
$
\dot P
= 18.713(4) × 10−13 s/s is reported. The observations were carried out on two high-sensitivity radio telescopes of the Pushchino Radio Astronomy
Observatory: the Large Phased Array at 111MHz and the DKR-1000 at 40MHz.Mean pulse profiles are presented; the measured flux
density is S
111 = 30 ± 20 mJy. The estimated distance derived from the dispersion measure, 27 pc/cm3, is 1.4 kpc, and the integrated radio luminosity is L
R
= 1.5 × 1027 erg/cm. Comparison with X-ray data shows an appreciable difference in the pulse duration (the radio pulse is about a factor
of 20 more narrow) and strong variations in the flux density. 相似文献
18.
I. Daniel G. Fiquet P. Gillet M. W. Schmidt M. Hanfland 《Physics and Chemistry of Minerals》1999,26(5):406-414
A pressure-volume-temperature data set has been obtained for lawsonite [CaAl2Si2O7(OH)2.H2O], using synchrotron X-ray diffraction and an externally heated diamond anvil cell. Unit-cell volumes were measured to 9.4
GPa and 767 K by angle dispersive X-ray diffraction using imaging plates. Phase changes were not observed within this pressure-temperature
range, and lawsonite compressed almost isotropically at constant temperature. The P-V-T data have been analyzed using a Birch-
Murnaghan equation of state and a linear equation of state expressed as β=–1/V0 (∂V/∂P)
T
. At room temperature, the derived equation of state parameters are: K
0=124.1 (18) GPa K'0 set to 4) and β–1=142.0(24) GPa, respectively. Our results are intermediate between previously reported measurements. The high-temperature
data show that the incompressibility of lawsonite decreases with increasing temperature to ∼500 K and then increases above.
Hence, the second order temperature derivative of the bulk modulus is taken into account in the equation of state; a fit of
the volume data yields K
0=123.9(18) GPa, (∂K/∂T)P=–0.111(3) GPa K–1, (∂2
K/∂T
2)P=0.28(6) 10–3 GPa K–2, α0=3.1(2) 10–5 K–1, assuming K'0=4.
Received: 2 June 1998 / Revised, accepted: 12 Ocotber 1998 相似文献
19.
X-ray powder diffraction measurements have been carried out at ESRF (Grenoble, France) on the ID30 beamline to study the
equation of state of 3T phengite (Dora-Maira massif, Italian western Alps) by a large volume cell up to P = 50 kbar and T = 1000 K. Several equations of state (EOS) models (the Vinet EOS, the Birch-Murnaghan EOS and its variants, a VT-polynomial expansion) have been used to interpolate the experimental data and discussed in the light of the results achieved.
The thermoelastic properties of 3T phengite (bulk modulus, its derivatives versus pressure or temperature, bulk thermal expansion)
have been obtained and an isochoric curve with slope P/T = 0.02 kbar/K has been calculated by means of the Vinet EOS. This slope value supports either the occurrence at the peak
conditions (about 30 kbar and 1000 K) of an originally Mg/Si-richer and stiffer phengite or a non-isochoric P-T retrograde path.
Received: 5 June 1998 / Revised, accepted: 12 December 1998 相似文献
20.
D. G. Isaak J. D. Carnes O. L. Anderson H. Cynn E. Hake 《Physics and Chemistry of Minerals》1998,26(1):31-43
The ambient pressure elastic properties of single-crystal TiO2 rutile are reported from room temperature (RT) to 1800 K, extending by more than 1200 oK the maximum temperature for which rutile elasticity data are available. The magnitudes
of the temperature derivatives decrease with increasing temperature for five of the six adiabatic elastic moduli (C
ij
). At RT, we find (units, GPa): C
11=268(1); C
33=484(2); C
44=123.8(2); C
66=190.2(5); C
23=147(1); and C
12=175(1). The temperature derivatives (units, GPa K−1) at RT are: (∂C
11/∂T)
P
=−0.042(5); (∂C
33/∂T)
P
=−0.087(6); (∂C
44/∂T)
P
=−0.0187(2); (∂C
66/∂T)
P
=−0.067(2); (∂C
23/∂T)
P
=−0.025; and (∂C
12/∂T)
P
−0.048(5). The values for K
S
(adiabatic bulk modulus) and μ (isotropic shear modulus) and their temperature derivatives are K
S
=212(1) GPa; μ=113(1) GPa; (∂K
S
/∂T)
P
=−0.040(4) GPa K−1; and (∂μ/∂T)
P
=−0.018(1) GPa K−1. We calculate several dimensionless parameters over a large temperature range using our new data. The unusually high values
for the Anderson-Gròneisen parameters at room temperature decrease with increasing temperature. At high T, however, these parameters are still well above those for most other oxides. We also find that for TiO2, anharmonicity, as evidenced by a non-zero value of [∂ln (K
T
)/∂lnV]
T
, is insignificant at high T, implying that for the TiO2 analogue of stishovite, thermal pressure is independent of volume (or pressure). Systematic relations indicate that ∂2
K
S
/∂T∂P is as high as 7×10−4 K−1 for rutile, whereas ∂2μ/∂T∂P is an order of magnitude less.
Received: 19 September 1997 / Revised, accepted: 27 February 1998 相似文献