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111.
An expression for the coefficient of linear expansion of a linear lattice is obtained by using the thermodynamic Green's function method. 相似文献
112.
Results of calculation of channeling potentials in crystals using the local density theory are given. The linear muffin-tin orbitals method is used in the atomic spheres approximation (LMTO-ASA) to calculate the planar-averaged potential seen by MeV electrons and positrons channeled along (110) planes of diamond, Si, and Ge. The calculations thus include the spherical charge relaxation effects (“solid state effects”) in the solid but omits the non-spherical part. The calculated potentials are in excellent agreement with the empirical potentials derived from channeling radiation experiments, but are significantly different near the atomic planes from the potentials obtained from superposition of the atomic Thomas-Fermi statistical (Molière) potentials. Agreement of the potentials with the ones obtained from superposition of atomic Doyle-Turner potentials is reasonably good. Frequencies of emitted radiation from the channeled electrons and positrons are also calculated and compared to experiments. For the crystals considered, it is concluded that the solid state effects on the planar-averaged potential are moderate to small. It is expected that these effects should be more important for channeling in ionic solids. The deviation of the observed positron channeling radiation from the calculated values for Si and C indicates that the non-spherical part of the charge relaxation might be relatively important for these solids. 相似文献
113.
The spectral features of the electromagnetic radiation emitted from relativistically fast positrons and electrons channeled along major crystallographic directions and planes are very sensitive to the interatomic potential assumed between theprojectile and the target crystal. The effects are investigated of platelets present in diamond type Ia on the channeling radiation by assuming a imple model for these defects, as seen from (100),(110), and (111) planar directions. The results arequalitatively correct and for (110) planar channel, quantitative agreement with the experimental results is also satisfactory. 相似文献
114.
Debye-Waller factors of zinc, cadmium, and magnesium are determined from room temperature up to about their melting points by X-ray diffraction using a diffractometer, scintillation counter, chart recorder, and a specially designed furnace having a large volume of uniform temperature. For all the three metals the Debye-Waller factor B is found to rise rapidly at higher temperatures. It is shown for the first time that the deviations AB from the initial part of the curves varies exponentially with 1/T. When reduced values of B are plotted against reduced temperature, the points corresponding to all the three metals are found to fall approximately on the same curve. Thus the metals obey a “law of corresponding states”. A common relation, applicable to all the three metals, between the total anharmonic contribution to B and the melting temperature is established. 相似文献
115.
A. P. Pathak 《physica status solidi b》1971,46(1):83-87
Using a modified Hubbard approximation for the static dielectric function, numerical calculations of the screening charge density around a fixed foreign charge in an electron liquid are presented for values of rs corresponding to the metallic density range. The screening parameter has been taken to reproduce the compressibility limit properly. The results are compared with those based on the original Hubbard approximation as calculated by Langer and Vosko, and it is found that the difference is small but not negligible. 相似文献
116.
Hasmat Khan Malobi Seth Atanu Naskar Sunirmal Jana 《Journal of Sol-Gel Science and Technology》2018,88(2):359-370
Nano noble metal coating on surface patterned mesoporous semiconductor thin film can play an important role in enhancing visible light harvesting efficiency (LHE) towards improvement in photoelectrochemical (PEC) activity of the material. In this work, one-dimensional (1D) and two-dimensional (2D) mesoscale surface patterns have been created on sol–gel-based titanium tin oxide (TSO) nanostructured thin film on pure silica/indium tin oxide-coated glass by soft lithography. The TSO film matrix is observed to be mesoporous and semicrystalline as evidenced from the structural characterization by transmission electron microscopy and measurement of atmospheric ellipso-porosimetry, respectively. The 2D patterned film exhibits maximum LHE value in visible wavelength region. Further film surface modification has been carried out by depositing nano Au coating onto the bare patterned TSO films by a low temperature solution technique. Under visible light, a significant improvement in PEC activity is found and the gold-coated patterned 2D film shows higher visible LHE as well as >2.7 times higher photocurrent density than bare 2D film. This facile fabrication strategy can create an avenue toward improvement in LHE vis-à-vis the PEC activity of mesoporous mixed metal oxide semiconductor thin film. 相似文献
117.
The present article describes a working or combined calibration curve in laser-induced breakdown spectroscopic analysis, which is the cumulative result of the calibration curves obtained from neutral and singly ionized atomic emission spectral lines. This working calibration curve reduces the effect of change in matrix between different zone soils and certified soil samples because it includes both the species' (neutral and singly ionized) concentration of the element of interest. The limit of detection using a working calibration curve is found better as compared to its constituent calibration curves (i.e., individual calibration curves). The quantitative results obtained using the working calibration curve is in better agreement with the result of inductively coupled plasma–atomic emission spectroscopy as compared to the result obtained using its constituent calibration curves. 相似文献
118.
Raghav Pathak;Seyed Morteza Seyedpour;Bernd Kutschan;Andrea Thom;Silke Thoms;Tim Ricken; 《PAMM》2024,24(2):e202400047
The Antarctic sea ice, which undergoes annual freezing and melting, plays a significant role in the global climate cycle. Since satellite observations in the Antarctic region began, 2023 saw a historically unprecedented decrease in the extent of sea ice. Further ocean warming and future environmental conditions in the Southern Ocean will influence the extent and amount of ice in the Marginal Ice Zones (MIZ), the BioGeoChemical (BGC) cycles, and their interconnected relationships. The so-called pancake floes are a composition of a porous sea ice matrix with interstitial brine, nutrients, and biological communities inside the pores. The ice formation and salinity are both dependent on the ambient temperature. To realistically model these multiphasic and multicomponent coupled processes, the extended Theory of Porous Media (eTPM) is used to develop Partial Differential Equations (PDEs) based high-fidelity models capable of simulating the different seasonal variations in the region. All critical variables like salinity, ice volume fraction, and temperature, among others, are considered and have their equations of state. The phase transition phenomenon is approached through a micro-macro linking scheme. In this paper, a phase-field solidification model [4] coupled with salinity is used to model the microscale freezing processes and up-scaled to the macroscale eTPM model. The evolution equations for the phase field model are derived following Landau-Ginzburg order parameter gradient dynamics and mass conservation of salt allowing to model the salt trapped inside the pores. A BGC flux model for sea ice is set up to simulate the algal species present in the sea ice matrix. Ordinary differential equations (ODE) are employed to represent the diverse environmental factors involved in the growth and loss of distinct BGC components. Processes like photosynthesis are dependent on temperature and salinity, which are derived through an ODE-PDE coupling with the eTPM model. Academic simulations and results are presented as validation for the mathematical model. These high-fidelity models eventually lead to their incorporation into large-scale global climate models. 相似文献
119.
Pranjal Pathak Kriti Shrivastava Takayuki Ichikawa Ankur Jain Rini Singh 《Molecules (Basel, Switzerland)》2022,27(13)
The hunt for a cleaner energy carrier leads us to consider a source that produces no toxic byproducts. One of the targeted alternatives in this approach is hydrogen energy, which, unfortunately, suffers from a lack of efficient storage media. Solid-state hydrogen absorption systems, such as lithium amide (LiNH2) systems, may store up to 6.5 weight percent hydrogen. However, the temperature of hydrogenation and dehydrogenation is too high for practical use. Various molar ratios of LiNH2 with sodium hydride (NaH) and potassium hydride (KH) have been explored in this paper. The temperature of hydrogenation for LiNH2 combined with KH and NaH was found to be substantially lower than the temperature of individual LiNH2. This lower temperature operation of both LiNH2-NaH and LiNH2-KH systems was investigated in depth, and the eutectic melting phenomenon was observed. Systematic thermal studies of this amide-hydride system in different compositions were carried out, which enabled the plotting of a pseudo-binary phase diagram. The occurrence of eutectic interaction increased atomic mobility, which resulted in the kinetic modification followed by an increase in the reactivity of two materials. For these eutectic compositions, i.e., 0.15LiNH2-0.85NaH and 0.25LiNH2-0.75KH, the lowest melting temperature was found to be 307 °C and 235 °C, respectively. Morphological studies were used to investigate and present the detailed mechanism linked with this phenomenon. 相似文献
120.
Kriti Pathak Sourav Gayen Suvam Saha Chandan Nandi Shivankan Mishra Prof. Dr. Sundargopal Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(18):e202104393
Treatment of [Cp*RuCl2]2, 1 , [(COD)IrCl]2, 2 or [(p-cymene)RuCl2]2, 3 (Cp*=η5-C5Me5, COD= 1,5-cyclooctadiene and p-cymene=η6-iPrC6H4Me) with heterocyclic borate ligands [Na[(H3B)L], L1 and L2 ( L1 : L=amt, L2 : L=mp; amt=2-amino-5-mercapto-1,3,4-thiadiazole, mp=2-mercaptopyridine) led to the formation of borate complexes having uncommon coordination. For example, complexes 1 and 2 on reaction with L1 and L2 afforded dihydridoborate species [LAM(μ-H)2BHL] 4 – 6 ( 4 : LA=Cp*, M=Ru, L=amt; 5 : LA=Cp*, M=Ru, L=mp; 6 : LA=COD, M=Ir, L=mp). On the other hand, treatment of 3 with L2 yielded cis- and trans-bis(dihydridoborate) species, [Ru{(μ-H)2BH(mp)}2], cis- 7 and trans- 7 . The isolation and structural characterization of fac- and mer-[Ru{(μ-H)2BH(mp)}{(μ-H)BH(mp)2}], 8 from the same reaction offered an insight into the behaviour of these dihydridoborate species in solution. Fascinatingly, despite having reduced natural charges on Ru centres both at cis-and trans- 7 , they underwent hydroboration reaction with alkynes that yielded both Markovnikov and anti-Markovnikov addition products, 10 a – d . 相似文献