scholarly journals О возможных состояниях кристаллической структуры, предшествующих фазовому переходу в кристаллах Zn-=SUB=-1-x-=/SUB=-V-=SUB=-x-=/SUB=-Se (0.01≤ x≤0.10)

2019 ◽  
Vol 61 (1) ◽  
pp. 42
Author(s):  
В.И. Максимов ◽  
Е.Н. Максимова ◽  
Т.П. Суркова ◽  
А.П. Вохмянин
Keyword(s):  
Wave Vector ◽  
Reciprocal Lattice ◽  
Short Wave ◽  
Neutron Diffraction Study ◽  
Vanadium Content ◽  
Atomic Displacements ◽  
Fcc Lattice ◽  
Structure State ◽  
Distortion Type ◽  
First Time

AbstractThe systematic new formations observed in the reciprocal lattice of the cubic structural modification of a II–VI compound are characterized using a detailed neutron diffraction study of bulk semiconducting ZnSe crystals with an increased vanadium content. Direct evidence that the additional sites k = (1/3 1/3 1/3) 2π/ a ( k is the wave vector and a is cubic unit cell parameter) observed by neutron scattering in the crystals, in the case when they belong to mutually penetrated rotated sublattices, contain a superstructure contribution formed by short-wave deformation, is obtained for the first time. This structure state is determined as a pretransition to the concentration fcc–hcp phase transformation, and the basis functions that allow one to analyze atomic displacements, the correlation between which create distortion-type superstructures, are indicated for the transition through one-arm channel, considering the transitions by the star of wave vector k _5 of the fcc lattice.

Effects of Higher-Order Laue Zone reflections on structure images

1993 ◽  
Vol 51 ◽  
pp. 450-451
Author(s):  
H. S. Kim ◽  
S. S. Sheinin
Keyword(s):  
Wave Vector ◽  
Theoretical Calculations ◽  
Reciprocal Lattice ◽  
Image Plane ◽  
Bloch Wave ◽  
Dynamical Theory ◽  
Higher Order ◽  
Lattice Image ◽  
Lattice Vector ◽  
Image Position

The importance of image simulation in interpreting experimental lattice images is well established. Normally, in carrying out the required theoretical calculations, only zero order Laue zone reflections are taken into account. In this paper we assess the conditions for which this procedure is valid and indicate circumstances in which higher order Laue zone reflections may be important. Our work is based on an analysis of the requirements for obtaining structure images i.e. images directly related to the projected potential. In the considerations to follow, the Bloch wave formulation of the dynamical theory has been used.The intensity in a lattice image can be obtained from the total wave function at the image plane is given by: where ϕg(z) is the diffracted beam amplitide given by In these equations,the z direction is perpendicular to the entrance surface, g is a reciprocal lattice vector, the Cg(i) are Fourier coefficients in the expression for a Bloch wave, b(i), X(i) is the Bloch wave excitation coefficient, ϒ(i)=k(i)-K, k(i) is a Bloch wave vector, K is the electron wave vector after correction for the mean inner potential of the crystal, T(q) and D(q) are the transfer function and damping function respectively, q is a scattering vector and the summation is over i=l,N where N is the number of beams taken into account.

scholarly journals Spatial aliasing and distortion of energy distribution in the wave vector domain under multi-spacecraft measurements

2009 ◽  
Vol 27 (8) ◽  
pp. 3031-3042 ◽  
Author(s):  
Y. Narita ◽  
K.-H. Glassmeier
Keyword(s):  
Energy Distribution ◽  
Brillouin Zone ◽  
Wave Vector ◽  
Flow Direction ◽  
Reciprocal Lattice ◽  
Periodic Pattern ◽  
Lattice Vector ◽  
Model Calculations ◽  
Spatial Aliasing ◽  
Spacecraft Data

Abstract. Aliasing is a general problem in the analysis of any measurements that make sampling at discrete points. Sampling in the spatial domain results in a periodic pattern of spectra in the wave vector domain. This effect is called spatial aliasing, and it is of particular importance for multi-spacecraft measurements in space. We first present the theoretical background of aliasing problems in the frequency domain and generalize it to the wave vector domain, and then present model calculations of spatial aliasing. The model calculations are performed for various configurations of the reciprocal vectors and energy spectra or distribution that are placed at different positions in the wave vector domain, and exhibit two effects on aliasing. One is weak aliasing, in which the true spectrum is distorted because of non-uniform aliasing contributions in the Brillouin zone. It is demonstrated that the energy distribution becomes elongated in the shortest reciprocal lattice vector direction in the wave vector domain. The other effect is strong aliasing, in which aliases have a significant contribution in the Brillouin zone and the energy distribution shows a false peak. These results give a caveat in multi-spacecraft data analysis in that spectral anisotropy obtained by a measurement has in general two origins: (1) natural and physical origins like anisotropy imposed by a mean magnetic field or a flow direction; and (2) aliasing effects that are imposed by the configuration of the measurement array (or the set of reciprocal vectors). This manuscript also discusses a possible method to estimate aliasing contributions in the Brillouin zone based on the measured spectrum and to correct the spectra for aliasing.

scholarly journals Geology and Geothermal Setting of Tompaso Geothermal System, Indonesia, with Comparisons of Andesite Alteration Patterns with Wairakei, New Zealand

2021 ◽  
Author(s):  
◽  
Kartika Palupi Savitri
Keyword(s):  
Hydrothermal Alteration ◽  
Short Wave ◽  
Age Dating ◽  
Core Material ◽  
Geothermal System ◽  
Scattered Electron ◽  
Subsurface Geology ◽  
North Sulawesi ◽  
Alteration Processes ◽  
First Time

<p>Tompaso geothermal system is a typical volcanic arc geothermal system in North Sulawesi, Indonesia. Although situated close to the Tondano caldera, subsurface lithologies and structures do not show any evidence for caldera-related features and the system is inferred to be related to the andesitic Soputan volcano. The subsurface geology of Tompaso consists of Tuff B unit, Rhyolite unit, Andesite B unit, Pitchstone unit, Pyroclastic Breccia unit,Andesite A unit, Pumice unit, and Tuff A unit, respectively, from the oldest penetrated unit. The silicic Pitchstone and Rhyolite units are presumed to be sourced from the same magma chamber. Petrological and mineralogical observations using binocular and petrographic microscopy, short-wave infrared (SWIR) analysis, and back-scattered electron (BSE) imaging combined with energy dispersive X-ray spectroscopy (EDS) have been applied to cuttings and limited core material from three boreholes: LHD-26, LHD-27, and LHD-32. Age dating has not been undertaken and, thus, conclusions on correlations between subsurface geology inferred here with surface formation groupings from previous works cannot be drawn.  Tompaso geothermal system is characterised primarily by variations in the fracturing within the reservoir. Secondary mineralogy and the structure of present-day temperature of the system suggest that the movement of hydrothermal fluids at Tompaso is controlled by faults: the Soputan, Tempang, and A-A’ faults, the last defined for the first time in this thesis. Soputan Fault controls the outflow of the system. On the other hand, the influence of Tempang and A-A’ faults is dominant only in the upper portion of the system. The A-A’ fault likely acts as a channel for cooler meteoric surface water, while the Tempang Fault is inferred to have experienced self-sealing and appears to be an impermeable structure in the system. The self-sealing process of the Tempang Fault and/or the introduction of meteoric water through the A-A’ fault may be related to the cooling of the northern and western part of the system.  The challenges in identifying protoliths in active geothermal areas is addressed here through studies of the influence of andesite textures on the preferences of hydrothermal alteration processes. Wairakei andesites were chosen for comparison to Tompaso andesites, especially because of its different geological setting and geothermal reservoir structure. The results suggest that mineral composition and arrangement affect the preference of hydrothermal alteration on andesites.</p>

scholarly journals Geology and Geothermal Setting of Tompaso Geothermal System, Indonesia, with Comparisons of Andesite Alteration Patterns with Wairakei, New Zealand

2021 ◽  
Author(s):  
◽  
Kartika Palupi Savitri
Keyword(s):  
Hydrothermal Alteration ◽  
Short Wave ◽  
Age Dating ◽  
Core Material ◽  
Geothermal System ◽  
Scattered Electron ◽  
Subsurface Geology ◽  
North Sulawesi ◽  
Alteration Processes ◽  
First Time

<p>Tompaso geothermal system is a typical volcanic arc geothermal system in North Sulawesi, Indonesia. Although situated close to the Tondano caldera, subsurface lithologies and structures do not show any evidence for caldera-related features and the system is inferred to be related to the andesitic Soputan volcano. The subsurface geology of Tompaso consists of Tuff B unit, Rhyolite unit, Andesite B unit, Pitchstone unit, Pyroclastic Breccia unit,Andesite A unit, Pumice unit, and Tuff A unit, respectively, from the oldest penetrated unit. The silicic Pitchstone and Rhyolite units are presumed to be sourced from the same magma chamber. Petrological and mineralogical observations using binocular and petrographic microscopy, short-wave infrared (SWIR) analysis, and back-scattered electron (BSE) imaging combined with energy dispersive X-ray spectroscopy (EDS) have been applied to cuttings and limited core material from three boreholes: LHD-26, LHD-27, and LHD-32. Age dating has not been undertaken and, thus, conclusions on correlations between subsurface geology inferred here with surface formation groupings from previous works cannot be drawn.  Tompaso geothermal system is characterised primarily by variations in the fracturing within the reservoir. Secondary mineralogy and the structure of present-day temperature of the system suggest that the movement of hydrothermal fluids at Tompaso is controlled by faults: the Soputan, Tempang, and A-A’ faults, the last defined for the first time in this thesis. Soputan Fault controls the outflow of the system. On the other hand, the influence of Tempang and A-A’ faults is dominant only in the upper portion of the system. The A-A’ fault likely acts as a channel for cooler meteoric surface water, while the Tempang Fault is inferred to have experienced self-sealing and appears to be an impermeable structure in the system. The self-sealing process of the Tempang Fault and/or the introduction of meteoric water through the A-A’ fault may be related to the cooling of the northern and western part of the system.  The challenges in identifying protoliths in active geothermal areas is addressed here through studies of the influence of andesite textures on the preferences of hydrothermal alteration processes. Wairakei andesites were chosen for comparison to Tompaso andesites, especially because of its different geological setting and geothermal reservoir structure. The results suggest that mineral composition and arrangement affect the preference of hydrothermal alteration on andesites.</p>

Регистрация высокочастотных рельефно-фазовых голографических структур на фотоматериале ПФГ-04

2021 ◽  
Vol 47 (21) ◽  
pp. 13
Author(s):  
Н.М. Ганжерли ◽  
С.Н. Гуляев ◽  
И.А. Маурер ◽  
А.В. Архипов
Keyword(s):  
Spatial Frequency ◽  
Uv Radiation ◽  
Diffraction Efficiency ◽  
High Frequency ◽  
Short Wave ◽  
Destructive Effect ◽  
Holographic Gratings ◽  
New Variant ◽  
First Time ◽  
Relief Phase

A new variant of processing photographic plates for holography based on dichromed gelatin PFG-04 (produced by JSC "Slavich Company", Pereslavl-Zalessky) for the manufacture of high-frequency relief–phase holographic gratings with a spatial frequency up to 1500 mm-1 is proposed. The technology is based on the selective destructive effect of short-wave UV radiation on gelatin and subsequent etching of the layer with various reagents. For the first time, relief-phase high-frequency holographic gratings with a maximum diffraction efficiency of 67% were obtained on PFG-04 photographic plates.

scholarly journals Sr1/2Ce5/14□1/7WO4: a new modulated ternary scheelite compound

2017 ◽  
Vol 73 (3) ◽  
pp. 466-473 ◽  
Author(s):  
Rafael Hernandez Damascena dos Passos ◽  
Madjid Arab ◽  
Carlson Pereira de Souza ◽  
Christine Leroux
Keyword(s):  
Band Gap ◽  
High Resolution Electron Microscopy ◽  
Partial Ordering ◽  
Promising Candidate ◽  
Atomic Displacements ◽  
Violet Luminescence ◽  
Resolution Electron ◽  
20 Nm ◽  
Cation Sites ◽  
First Time

For the first time, a ternary tetragonal scheelite structure tungstate with strontium and cerium cations, (Sr,Ce)WO4, was synthesized. As much as 35% Ce could be inserted into the structure, leaving 1\over 7 of the (Sr,Ce) cation sites vacant. Partial ordering of Sr and Ce, with atomic displacements, were shown by high-resolution electron microscopy. Two-dimensional incommensurate modulations occur in this material, in small domains 20 nm in size. The band gap of this compound is significantly lower than the band gap of SrWO4and this was related to the distortions of WO4and (Sr,Ce)O8polyhedra. The band gap value of 3.2 eV makes Sr1/2Ce5/14□1/7WO4a promising candidate for violet luminescence.

Ferroic phase transition in LaEr(MoO4)3

2013 ◽  
Vol 28 (S2) ◽  
pp. S86-S93
Author(s):  
A. Hernández-Suárez ◽  
C. Guzmán-Afonso ◽  
J. López-Solano ◽  
C. González-Silgo ◽  
M. E. Torres ◽  
...  
Keyword(s):  
Phase Transition ◽  
Density Functional ◽  
Thermal Dependence ◽  
Functional Theory ◽  
Space Group ◽  
X Ray ◽  
Atomic Displacements ◽  
Tetragonal System ◽  
First Time ◽  
Conventional Solid State Synthesis

The ferroic phase transition in LaEr(MoO4)3 has been analyzed for the first time. It has been confirmed that this compound undergoes a phase transition from a tetragonal system (paraelectric-paraelastic phase), with space group P-421m [β-Gd2(MoO4)3 averaged phase] to an orthorhombic system (ferroelectric-ferroelastic phase), with space group Pba2 [β'-Gd2(MoO4)3 phase] in a reversible process. This phenomenon, together with the observed demixing at high temperature has been studied using different techniques. LaEr(MoO4)3 samples have been obtained by the conventional solid-state synthesis. The thermal dependence of the crystal structure was studied by powder X-ray and neutron diffraction, following a new refining procedure in which the symmetry modes of atomic displacements from the paraelectric-paraelastic structure were analyzed. Dielectric spectroscopy measurements have confirmed the structural results, showing a very smooth phase transition. Finally, calculations within the framework of Density Functional Theory show a behavior of the lattice parameters similar to that observed in our experiments.

scholarly journals Thermal remote sensing from Airborne Hyperspectral Scanner data in the framework of the SPARC and SEN2FLEX projects: an overview

2009 ◽  
Vol 6 (3) ◽  
pp. 4107-4124
Author(s):  
J. A. Sobrino ◽  
J. C. Jiménez-Muñoz ◽  
P. J. Zarco-Tejada ◽  
G. Sepulcre-Cantó ◽  
E. de Miguel ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Near Infrared ◽  
Short Wave ◽  
Scanner Data ◽  
Data Errors ◽  
Spectral Bands ◽  
Field Campaigns ◽  
First Time

Abstract. The AHS (Airborne Hyperspectral Scanner) instrument has 80 spectral bands covering the visible and near infrared (VNIR), short wave infrared (SWIR), mid infrared (MIR) and thermal infrared (TIR) spectral range. The instrument is operated by Instituto Nacional de Técnica Aerospacial (INTA), and it has been involved in several field campaigns since 2004. This paper presents an overview of the work performed with the AHS thermal imagery provided in the framework of the SPARC and SEN2FLEX campaigns, carried out respectively in 2004 and 2005 over an agricultural area in Spain. The data collected in both campaigns allowed for the first time the development and testing of algorithms for land surface temperature and emissivity retrieval as well as the estimation of evapotranspiration from AHS data. Errors were found to be around 1.5 K for land surface temperature and 1 mm/day for evapotranspiration.

scholarly journals Люминесцентные свойства в видимом и коротковолновом ИК-спектральных диапазонах апатитов Sr-=SUB=-2-=/SUB=-La-=SUB=-8-x-=/SUB=-Tm-=SUB=-x-=/SUB=-(GeO-=SUB=-4-=/SUB=-)-=SUB=-6-=/SUB=-O-=SUB=-2-=/SUB=- (x= 0.1-1.0)

2020 ◽  
Vol 62 (8) ◽  
pp. 1252
Author(s):  
Я.В. Бакланова ◽  
О.А. Липина ◽  
Л.Л. Сурат ◽  
А.Ю. Чуфаров ◽  
А.П. Тютюнник ◽  
...  
Keyword(s):  
Infrared Region ◽  
Short Wave ◽  
Emission Lines ◽  
Blue Color ◽  
Solid State Method ◽  
Ultraviolet Excitation ◽  
Short Wave Infrared ◽  
First Time ◽  
Spectral Luminescence ◽  
Thermal Stability Of

The Sr2La8-xTmx(GeO4)6O2 (x = 0.1–1.0) solid solutions with the apatite structure were synthesized by the solid-state method for the first time, the spectral-luminescence properties were studied and the prospects of these compounds as phosphors of the visible and short-wave infrared ranges were demonstrated. The luminescence of germanates Sr2La8-xTmx(GeO4)6O2 under ultraviolet excitation is characterized by high blue color purity and color coordinates close to commercially available phosphors. In addition, it was shown that Sr2La8-xTmx(GeO4)6O2 compounds efficiently convert 808 nm laser radiation into a series of emission lines in the spectral range of 1.3–2.2 µm due to successive 3H4 → 3F4 and 3F4 →3H6 transitions in Tm3+ ions. The Sr2La7.6Tm0.4(GeO4)6O2 germanate with a maximum emission intensity in the short-wave infrared region demonstrates high thermal stability of luminescence in the range of 30–220 °С.

First accurate location of two proton sites in tourmaline: A single-crystal neutron diffraction study of oxy-dravite

2014 ◽  
Vol 78 (3) ◽  
pp. 681-692 ◽  
Author(s):  
G. D. Gatta ◽  
F. Bosi ◽  
G. J. McIntyre ◽  
H. Skogby
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Study ◽  
Structure Refinement ◽  
Site Occupancy ◽  
Bond Distance ◽  
Neutron Diffraction Study ◽  
Fold Axis ◽  
Absorption Bands ◽  
First Time

AbstractA single-crystal neutron diffraction study of oxy-dravite from Osarara (Narok district, Kenya) was performed. Intensity data were collected in Laue geometry at 10 K and anisotropic-structure refinement was undertaken. For the first time, two independent H sites were refined unambiguously for a mineral belonging to the tourmaline supergroup and located at 0.26, 0.13, 0.38 (labelled as H3, site occupancy ∼98%) and at 0, 0, 0.9 (labelled as H1, site occupancy ∼25%). The H-bonding scheme can thus be defined as follows: (1) the O at the O3 site acts as a ‘donor’ and the O at the O5 site as ‘acceptor’, the refined O3–H3 bond distance is 0.972(2) Å (and 0.9946 Å corrected for “riding motion”), H3⋯O5 = 2.263(2) Å, O3⋯O5 = 3.179(1) Å and O3–H3⋯O5 = 156.6(1)°; (2) the oxygen at the O1 site acts as a ‘donor’ and the O atoms at O4 and O5 as ‘acceptors’, the refined O1–H1 bond distance is 0.958(8) Å (and 0.9833 Å corrected for “riding motion”), H1⋯O4 = 2.858(6) Å, O1⋯O4 = 3.378(1) Å and O1–H1⋯O4 = 115.12(1)°, whereas H1⋯O5 = 2.886(6) Å, O1⋯O5 = 3.444(1) Å and O1–H1⋯O5 = 118.23(1)°. A further test refinement was performed with the H1 site out of the three-fold axis (at 0.02, 0.01, 0.90); this leads to O1–H1 = 0.995(8) Å (and 1.0112 Å corrected for “riding motion”), H1⋯O4 = 2.747(6) Å and O1–H1⋯O4 = 121.7(4)°, whereas H1⋯O5 = 2.654(9) Å and O1–H1⋯O5 = 136.5(6)°. Bond-valence analysis shows that the H-bonding strength involving O3 is stronger than that involving O1: ∼0.11 and <0.05 valence units, respectively.The refined angle between the O3–H3 vector and [0001] is 3.40(9)°. Such a small angle is in line with a pleochroic scheme for the OH-stretching absorption bands measured by infrared spectroscopy.

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