220 research outputs found
ТЕОСОФИЯ: ГЕНЕЗИС И АКТУАЛИЗАЦИЯ УЧЕНИЯ
У статті розглядається сутність теософії в її історико-філософському генезисі,
представленому у вченні неоплатоников, гностиків, середньовічних і ренесансних містиків.
Визначається сутність теософії як вчення синкретичної єдності ірраціонально-раціонального
збагнення глибини реальності. Специфічність теософії розкривається порівняно з філософією,
через визначення джерела знання, предмету і методу пізнання. Представлена актуалізація
теософії через сучасну діяльність Міжнародного теософського товариства і спадщину
О.П.Блаватськой. Вказується натрансформаційні змінимісії теософії, яка з езотеричного вчення
переходить в статус морально-етичного корелята розвитку соціальних інститутів іжиттєвого
простору людини.В статье рассматривается сущность теософии в её историко-философском генезисе,
представленном в учении неоплатоников, гностиков, средневековых и ренессансных
мистиков. Определяется сущность теософии как учения синкретического единства
иррационально-рационального постижения глубины реальности. Специфичность теософии
раскрывается в сравнении с философией, через определение источника знания, предмета и
метода познания. Представлена актуализация теософии через современную деятельность
Международного теософского общества и наследие Е.П.Блаватской. Указывается на
трансформационные изменения миссии теософии, которая из эзотерического учения переходит
в статус морально-нравственного коррелята развития социальных институтов и жизненного
пространства человека.In the articleessence of theosophy is examined inits historicaland philosophicalgenesis, presented
in thestudies of neoplatonizmus, gnostics,medieval andrenaissancemystics. Essence oftheosophy as
studies of syncretismunity of the irrational-rational understanding of depth of reality is determined.
Specificity of theosophy opens up by comparison to philosophy, through determination of source of
knowledge, object andmethod of cognition.Actualization of theosophy is presented throughmodern
activity ofInternational theosophicalsociety andlegacy ofE.P.Blavatskoy. Specified on transformation
changes themission of theosophywhich fromesoteric studies passes to status ofmoral-moral correlate
of development of social institutes and vital space ofman
Determination of the high-pressure crystal structure of BaWO4 and PbWO4
We report the results of both angle-dispersive x-ray diffraction and x-ray
absorption near-edge structure studies in BaWO4 and PbWO4 at pressures of up to
56 GPa and 24 GPa, respectively. BaWO4 is found to undergo a pressure-driven
phase transition at 7.1 GPa from the tetragonal scheelite structure (which is
stable under normal conditions) to the monoclinic fergusonite structure whereas
the same transition takes place in PbWO4 at 9 GPa. We observe a second
transition to another monoclinic structure which we identify as that of the
isostructural phases BaWO4-II and PbWO4-III (space group P21/n). We have also
performed ab initio total energy calculations which support the stability of
this structure at high pressures in both compounds. The theoretical
calculations further find that upon increase of pressure the scheelite phases
become locally unstable and transform displacively into the fergusonite
structure. The fergusonite structure is however metastable and can only occur
if the transition to the P21/n phases were kinetically inhibited. Our
experiments in BaWO4 indicate that it becomes amorphous beyond 47 GPa.Comment: 46 pages, 11 figures, 3 table
Monazite-type SrCrO4 under compression
We report a high-pressure study of monoclinic monazite-type SrCrO4 up to 26 GPa. Therein we combined x-ray diffraction, Raman, and optical-absorption measurements with ab initio calculations, to find a pressure-induced structural phase transition of SrCrO4 near 8–9 GPa. Evidence of a second phase transition was observed at 10–13 GPa. The crystal structures of the high-pressure phases were assigned to the tetragonal scheelite-type and monoclinic AgMnO4-type structures. Both transitions produce drastic changes in the electronic band gap and phonon spectrum of SrCrO4. We determined the pressure evolution of the band gap for the low- and high-pressure phases as well as the frequencies and pressure dependencies of the Raman-active modes. In all three phases most Raman modes harden under compression, however the presence of low-frequency modes which gradually soften is also detected. In monazite-type SrCrO4, the band gap blueshifts under compression, but the transition to the scheelite phase causes an abrupt decrease of the band gap in SrCrO4. Calculations showed good agreement with experiments and were used to better understand the experimental results. From x-ray-diffraction studies and calculations we determined the pressure dependence of the unit-cell parameters of the different phases and their ambient-temperature equations of state. The results are compared with the high-pressure behavior of other monazites, in particular PbCrO4. A comparison of the high-pressure behavior of the electronic properties of SrCrO4 (SrWO4) and PbCrO4 (PbWO4) will also be made. Finally, the possible occurrence of a third structural phase transition is discussed
High-pressure phase transitions and compressibility of wolframite-type tungstates
This paper reports an investigation on the phase diagram and compressibility of wolframite-type tungstates by means of x-ray powder diffraction and absorption in a diamond-anvil cell and ab initio calculations. X-ray diffraction experiments show that monoclinic wolframite-type MgWO4 suffers at least two phase transitions, the first one being to a triclinic polymorph with a structure similar to that of CuWO4 and FeMoO4-II. The onset of each transition is detected at 17.1 and 31 GPa. In ZnWO4 the onset of the monoclinic-triclinic transition has been also found at 16.7 GPa. This transition does not involve any change in the atomic coordination as confirmed by x-ray absorption measurements. These findings are supported by density-functional theory calculations, which predict the occurrence of additional transitions upon further compression. Calculations have been also performed for wolframite-type MnWO4, which is found to have an antiferromagnetic configuration. In addition, our study reveals details of the local-atomic compression in MgWO4 and ZnWO4. In particular, below the transition pressure the ZnO6 and equivalent polyhedra tend to become more regular, whereas, the WO6 octahedra remain almost unchanged. Fitting the pressure-volume data we obtained the equation of state for the low-pressure phase of MgWO4 and ZnWO4. These and previous results on MnWO4 and CdWO4 are compared with the calculations. The compressibility of wolframite-type tungstates is also systematically discussed. Finally Raman spectroscopy measurements and lattice dynamics calculations are presented for MgWO4
Angle-resolved photoemission study and first principles calculation of the electronic structure of GaTe
The electronic band structure of GaTe has been calculated by numerical atomic
orbitals density-functional theory, in the local density approximation. In
addition, the valence-band dispersion along various directions of the GaTe
Brillouin zone has been determined experimentally by angle-resolved
photoelectron spectroscopy. Along these directions, the calculated valence-band
structure is in good concordance with the valence-band dispersion obtained by
these measurements. It has been established that GaTe is a direct-gap
semiconductor with the band gap located at the Z point, that is, at Brillouin
zone border in the direction perpendicular to the layers. The valence-band
maximum shows a marked \textit{p}-like behavior, with a pronounced anion
contribution. The conduction band minimum arises from states with a comparable
\textit{s}- \textit{p}-cation and \textit{p}-anion orbital contribution.
Spin-orbit interaction appears to specially alter dispersion and binding energy
of states of the topmost valence bands lying at . By spin-orbit, it is
favored hybridization of the topmost \textit{p}-valence band with deeper
and flatter \textit{p}-\textit{p} bands and the valence-band minimum at
is raised towards the Fermi level since it appears to be determined by
the shifted up \textit{p}-\textit{p} bands.Comment: 7 text pages, 6 eps figures, submitted to PR
Phase transition systematics in BiVO4 by means of high-pressure-high-temperature Raman experiments
We report here high-pressure–high-temperature Raman experiments performed on
BiVO
4
. We characterized the fergusonite and scheelite phases (powder and single crystal samples) and the zircon polymorph (nanopowder). The experimental results are supported by ab initio calculations, which, in addition, provide the vibrational patterns. The temperature and pressure behavior of the fergusonite lattice modes reflects the distortions associated with the ferroelastic instability. The linear coefficients of the zircon phase are in sharp contrast to the behavior observed in the fergusonite phase. The boundary of the fergusonite-to-scheelite second-order phase transition is given by
T
F
−
Sch
(
K
)
=
−
166
(
8
)
P
(
GPa
)
+
528
(
5
)
. The zircon-to-scheelite, irreversible, first-order phase transition takes place at
T
Z
−
Sch
(
K
)
=
−
107
(
8
)
P
(
GPa
)
+
690
(
10
)
. We found evidence of additional structural changes around 15.7 GPa, which in the downstroke were found to be not reversible. We analyzed the anharmonic contribution to the wave-number shift in fergusonite using an order parameter. The introduction of a critical temperature depending both on temperature and pressure allows for a description of the results of all the experiments in a unified way
New polymorph of InVO4: A high-pressure structure with six-coordinated vanadium
This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Inorganic Chemestry, copyright © American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/ic402043xA new wolframite-type polymorph of InVO4 is identified under compression near 7 GPa by in situ high-pressure (HP) X-ray diffraction (XRD) and Raman spectroscopic investigations on the stable orthorhombic InVO4. The structural transition is accompanied by a large volume collapse (Delta V/V = -14%) and a drastic increase in bulk modulus (from 69 to 168 GPa). Both techniques also show the existence of a third phase coexisting with the low- and high-pressure phases in a limited pressure range close to the transition pressure. XRD studies revealed a highly anisotropic compression in orthorhombic InVO4. In addition, the compressibility becomes nonlinear in the HP polymorph. The volume collapse in the lattice is related to an increase of the polyhedral coordination around the vanadium atoms. The transformation is not fully reversible. The drastic change in the polyhedral arrangement observed at the transition is indicative of a reconstructive phase transformation. The HP phase here found is the only modification of InVO4 reported to date with 6-fold coordinated vanadium atoms. Finally, Raman frequencies and pressure coefficients in the low- and high-pressure phases of InVO4 are reported.This research supported by the Spanish government MINECO under Grant Nos. MAT2010-21270-C04-01/04 and CSD2007-00045. O.G. acknowledges support from Vicerrectorado de Investigacion y Desarrollo of UPV (Grant No. UPV2011-0914 PAID-05-11 and UPV2011-0966 PAID-06-11). S.N.A. acknowledges support provided by Universitat de Valencia during his visit to it. B.G.-D. acknowledges the financial support from MINECO through the FPI program.Errandonea, D.; Gomis Hilario, O.; García-Domene, B.; Pellicer Porres, J.; Katari, V.; Achary, SN.; Tyagi, AK.... (2013). New polymorph of InVO4: A high-pressure structure with six-coordinated vanadium. Inorganic Chemistry. 52(21):12790-12798. https://doi.org/10.1021/ic402043xS1279012798522
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