Wyniki wyszukiwania - Biblioteka Nauki

1

Thermodynamic properties of liquid solution Ag-Tl-Te

100%

Zaleska E. , Sztuba Z. , Sroka A. , Gaweł W.

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1998

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tom Vol. 72, nr 7

1228-1236

EN

Excess partial molar thermodynamic functions for the Ag-Tl-Te liquid solutions have been determined along the sections: X-Ag:X-Tc=1:4, 2:3, 1:1 and 3:2. The thermodynamic properties have been discussed in dependence on the number and type of associates existing in the liquid.

2

An analytic equation of state based on analytic mean-field potential approach and application to three phases of metallic Zirconium

100%

Tian R. , Sun J. , Yang W. , Xue X. , Yu F.

Open Physics

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2008

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tom 6

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nr 3

704-710

EN

The analytic mean-field approach (AMFP) was applied to study the thermodynamic properties of Zirconium (Zr). The analytic expressions for the Helmholtz free energy, internal energy and equation of state have been derived. The formalism for the case of the Morse potential is used in this work. The four potential parameters are determined by fitting the molar volume of the three phases of Zr. The calculated molar volume of α, β and ω Zr are in fairly good agreement with the available experimental data. The results presented in this paper verify that the AMFP is a useful approach to study the thermodynamic properties of Zr. Furthermore, we predict the variation of the relationship of free energy and internal energy versus the molar volume at various temperatures and the dependence of the bulk modulus, the thermal expansion coefficient and the heat capacity on temperature at zero pressure of α, β and ω Zr.

3

Density Functional Calculations on a Double Hydrogen Bonded Dimer of (p-Methoxyphenyl)thiosemicarbazide

100%

Zhao P. , Li R. , Zhang L. , Jian F.

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2006

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tom Vol. 80, nr 12

2031-2039

EN

Density functional theory (DFT) calculations on a double hydrogen-bonded dimer of (p-methoxyphenyl)thiosemicarbazide were carried out at B3LYP/6-31G* level. The optimized geometry of the dimer closely resembles that in the crystal. The calculated results show that the total energy of the dimer is much lower than the sum of energies of the two monomers, and the average strength of the double hydrogen bond is about 21.92 kJ/mol. In order to probe the origin of the interactions in the dimer, natural bond orbital analyses have been performed. The thermodynamic properties of the title compound at different temperatures have also been calculated on the basis of vibrational analyses and the change of Gibbs free energy for dimerization of the twomonomers.GT = –18.40 kJ/mol at 298.15 K and 0.1MPa, which implies the spontaneous process of the dimer formation. The correlation graphs of Sm 0, Hm 0 and temperatures for the dimer are depicted.

4

Developing novel correlations for calculating natural gas thermodynamic properties

100%

Farzaneh-Gord M. , Rahbari H.

Chemical and Process Engineering

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2011

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tom 32

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nr 4

435-452

EN

Natural gas is a mixture of 21 components and it is widely used in industries and homes. Knowledge of its thermodynamic properties is essential for designing appropriate processes and equipment. This paper presents simple but precise correlations of how to compute important thermodynamic properties of natural gas. As measuring natural gas composition is costly and may not be effective for real time process, the correlations are developed based on measurable real time properties. The real time properties are temperature, pressure and specific gravity of the natural gas. Calculations with these correlations are compared with measured values. The validations show that the average absolute percent deviation (AAPD) for compressibility factor calculations is 0.674%, for density is 2.55%, for Joule-Thomson coefficient is 4.16%. Furthermore, in this work, new correlations are presented for computing thermal properties of natural gas such as enthalpy, internal energy and entropy. Due to the lack of experimental data for these properties, the validation is done for pure methane. The validation shows that AAPD is 1.31%, 1.56% and 0.4% for enthalpy, internal energy and entropy respectively. The comparisons show that the correlations could predict natural gas properties with an error that is acceptable for most engineering applications.

5

Elastic Anisotropic and Thermodynamic Properties of Two BC₇ Phases

100%

Xing M. , Li B. , Yu Z. , Chen Q.

Acta Physica Polonica A

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2017

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tom 132

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nr 4

1340-1346

EN

The structural, elastic, anisotropic, and thermodynamic properties of P3m1-BC₇ and Pmm2-BC₇ have been studied in this paper utilizing first-principles calculations. In comparison with the elastic properties of Pmm2-BC₇, P3m1-BC₇ exhibits slightly higher values in bulk modulus and B/G, with similar values in shear modulus, the Young modulus, and the Poisson ratio. The calculated Pugh modulus ratio (B/G) and the Poisson ratio demonstrates P3m1-BC₇ from brittle to ductile at 93.60 and 93.73 GPa, respectively. Calculations of shear anisotropic factor, universal elastic anisotropy index, shear modulus, the Young modulus, and the Poisson ratio for BC₇ then demonstrate that Pmm2-BC₇ exhibits a larger elastic anisotropy than P3m1-BC₇. Quasi-harmonic Debye model is finally applied to investigate the Debye temperature, the coefficient of thermal expansion, heat capacity and Grüneisen parameter of Pmm2-BC₇ and P3m1-BC₇.

6

The structural, elastic and thermodynamic properties of intermetallic compound CeGa2

100%

Çiftci Y. , Çolakoǧlu K. , Çoban C. , Deligöz E.

Open Physics

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2012

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tom 10

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nr 1

197-205

EN

The structural, elastic and thermodynamic characteristics of CeGa2 compound in the AlB2 (space group: P6/mmm) and the omega trigonal (space group: P-3m1) type structures are investigated using the methods of density functional theory within the generalized gradient approximation (GGA). The thermodynamic properties of the considered structures are obtained through the quasi-harmonic Debye model. The results on the basic physical parameters, such as the lattice constant, the bulk modulus, the pressure derivative of bulk modulus, the phase-transition pressure (P t) from P6/mmm to P-3m1 structure, the second-order elastic constants, Zener anisotropy factor, Poisson’s ratio, Young’s modulus, and the isotropic shear modulus are presented. In order to gain further information, the pressure and temperature-dependent behavior of the volume, the bulk modulus, the thermal expansion coefficient, the heat capacity, the entropy, Debye temperature and Grüneisen parameter are also evaluated over a pressure range of 0–6 GPa and a wide temperature range of 0–1800 K. The obtained results are in agreement with the available experimental and the other theoretical values.

7

A first-principles studies on TlX (X=P, As)

100%

Ciftci Y. , Colakoglu K. , Deligoz E.

Open Physics

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2008

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tom 6

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nr 4

802-807

EN

We present an ab initio study of the structural, electronic and thermodynamic properties of TlX(X=P,As). The plane-wave pseudopotential approach to the density-functional theory within the LDA and GGA approximations implemented in VASP (Viena Ab-initio Simulation Package) is used. The calculated lattice parameter, elastic constants, and band structures are compared with other available theoretical results, and good agreement is obtained. In addition, we have calculated the transition pressure (P t) from zinc-blende (ZB) to (rock-salt) NaCl structures, and have examined some thermodynamic properties.

8

Thermodynamic properties of semiconductor compounds studied based on Debye-Waller factors

88%

Van Hung N. , Toan N. C. , Ba Duc N. , Vuong D. Q.

Open Physics

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2015

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tom 13

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nr 1

EN

Thermodynamic properties of semiconductor compounds have been studied based on Debye-Waller factors (DWFs) described by the mean square displacement (MSD) which has close relation with the mean square relative displacement (MSRD). Their analytical expressions have been derived based on the statistical moment method (SMM) and the empirical many-body Stillinger-Weber potentials. Numerical results for the MSDs of GaAs, GaP, InP, InSb, which have zinc-blende structure, are found to be in reasonable agreement with experiment and other theories. This paper shows that an elements value for MSD is dependent on the binary semiconductor compound within which it resides.

9

Synthesis, Characterization and ab initio Calculations on 1-Phenyl-3-p-fluorophenyl-5-p-methoxyphenyl-2-pyrazoline

88%

Zhao P. S. , Li Y. F. , Guo H. M. , Wang X. , Jian F. F.

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2007

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tom Vol. 81, nr 10

1735-1735

EN

1-Phenyl-3-p-fluorophenyl-5-p-methoxyphenyl-2-pyrazoline has been synthesized and characterized by elemental analysis, IR, UV-Vis and X-ray single crystal diffraction. Ab initio calculations for the title compound have been carried out and the calculated results show that HF/6-311G** method can well reproduce the structural parameters. The theoretical electronic absorption spectra have been predicted by using 6-311G** and 6-311++G** basis sets and compared with the experimental values, indicating that HF-CIS method can well predict electronic absorption spectra for the system studied here. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between C 0 p,m , S 0 m , H 0 m and temperature.

10

Studies on the Interfacial Composition, Thermodynamic Properties and Structural Parameters of W/O Microemulsions Containing Surfactant-like Ionic Liquid

75%

Li Y. , Chai J. L. , Xue X. N. , Zhang Z. M.

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2009

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tom Vol. 83, nr 10

1809-1820

EN

The interfacial composition, ther mo dy namic prop er ties and struc ture pa ram e ters of the microemulsion systems con tain ing surfactant-like ionic liquid have been investigated with the dilution method of the W/O microemulsions. The interfacial parameters of Xa i , thermodynamic properties K, –Delta Go i o rghtwards arrow and structure parameters Re, Rw, Nd, Ns, Na have been calculated and discussed for microemulsion systems surfactant-like ionic liquid C12mimBr (C14mimBr, C16mimBr) / alcohol / alkane / water. The effects of water content, alcohols, alkanes, salinity and temperature on above parameters were dis cussed. The results show that with the in crease insalinity and the carbon chain length of both surfactant and alcohol, or with the decrease in the carbon chain length of the alkanes, the molar fraction of the alcohol at the interfacial layer (Xa i ) decreases, the formation of the micro - emulsion is more spontaneous in thermodynamics, and the droplets of the W/O microemulsion were enlarged. The size of the microemulsion droplets is sensitive to the water content, and increases significantly with increasing water content.

11

First-Principles Study of the Structural, Electronic, Magnetic and Thermal Properties of the Cr Doped Ge₆Mn₂Te₈ and Ge₆Fe₂Te₈ Systems

75%

Semari F. , Baki N. , Khachai H. , Yakoubi A. , Méçabih S. , Khenata R. , Shankar A. , Rai D. , Bouhemadou A.

Acta Physica Polonica A

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2017

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tom 132

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nr 4

1242-1250

EN

First-principles calculations have been used to study the structural, electronic, magnetic, and thermal properties of the Cr doped Ge₆Mn₂Te₈ and Ge₆Fe₂Te₈ systems. The calculations were performed using the full-potential linearized augmented plane wave plus local orbitals (FP-LAPW + LO) method based on the spin-polarized density functional theory. Additionally, the electronic exchange-correlation potential is approximated using the spin generalized gradient approximation. The structural properties of the Ge₅Mn₂CrTe₈ and Ge₅Fe₂CrTe₈ alloys are indicated by their corresponding lattice constants, values of the bulk moduli and their pressure derivatives. An analysis of the band structures and the densities of states indicate that for both alloys, they present nearly half-metallic ferromagnetism character. The band structure calculations are used to estimate the spin-polarized splitting energies, Δp_{x}(d) and Δp_{x}(pd) produced by the 3d Mn, 3d Fe and 3d Cr doped states as well as the s(p)-d exchange constants, N₀α (conduction band) and N₀β (valence band). It is observed that the p-d hybridization reduces the magnetic moment of the Mn and Fe atoms from their atomic charge values and create small local magnetic moments on the nonmagnetic Ge and Te sites. Furthermore, the calculations of the charge density indicate that both compounds have ionic bonding character. Through the quasi-harmonic Debye model, the effects of pressure P and temperature T on the bulk modulus B, the primitive cell volume V/V₀, the Debye temperature θ_{D}, the Grüneisen parameter γ, the heat capacity C_{V}, the entropy S, as well as the thermal expansion coefficient, α of the Ge₆Mn₂Te₈, Ge₅Mn₂CrTe₈, Ge₆Fe₂Te₈ and Ge₅Fe₂CrTe₈ alloys are predicted.

12

Developing novel correlations for calculating natural gas thermodynamic properties

75%

Farzaneh-Gord M. , Rahbari H.

|

13

The oxidation of palladium

63%

Pawlas-Foryst E.

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2008

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tom Vol. 53, iss. 4

1173-1175

EN

Thermodynamic properties of palladium oxide, PdO, were determined by means of ernf techniąue, using solid electrolyte galvanic cells: Pt, Pd, PdO|Zr02 + Y203|air, Pt with air reference electrode. The main experimental problem was to obtain both palladium and palladium oxide, as well in the form of powders, which was attained by complicated chemical procedurę. Gibbs energy of oxidation reaction was derived from emf values measured within temperaturę rangę: 843 - 1100 K, and standard thermodynamic functions were then calculated at room temperaturę, using the most recent Cp data. Comparison of ąuantities obtained in this study with other recent experimental values from literaturę and data from thermochemical compilations displays very good agreement.

PL

Własności termodynamiczne tlenku palladu wyznaczono metodą pomiaru siły elektromotorycznej odpowiednich ogniw galwanicznym ze stałym elektrolitem: Pt, Pd, PdO|Zr02 + Y203|air, Pt z powietrzną elektrodą odniesienia. Poważnym problemem było uzyskanie metalicznego palladu jak i jego tlenku w postaci proszku, co osiągnięto z pomocą skomplikowanej procedury chemicznej. Energię swobodną reakcji utleniania palladu wyznaczono ze zmierzonych sił elektromotorycznych w przedziale temperatur: 843 - 1100 K. Wartości standardowych funkcji termodynamicznych w temperaturze pokojowej obliczono przy pomocy najnowszych danych Cp. Porównanie wyników niniejszej pracy z rezultatami najnowszych badań innych autorów a także z wartościami z kompilacji danych termochemicznych wskazuje na bardzo dobrą zgodność.

14

Thermodynamic properties of intermetallic compounds in Al-Sc, Cu-Sc and Pb-Sc systems

63%

Shubin A. , Shunyaev K. , Yamshchikov L.

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2008

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tom Vol. 53, iss. 4

1119-1125

EN

The partial Gibbs free energies of formation of intermetallic compounds (IMC) in Al-Sc, Cu-Sc and Pb-Sc systems were determined by e.m.f. method. Electromotive forces of galvanic cells were measured in wide temperaturę rangę. The data obtained were used to find integral thermodynamic properties of IMC at 298.15 K. The integral Gibbs energy of Pb5Sc6 formation from solid scandium and liquid lead obtained from e.m.f. measurements can be described by the eąuation (at 650-1040 K): ΔfG (Pb5Sc6) = - (49.60 ± 1.1) + (3.63 ± 1.3) º1O-3 T, kJ/mol of atoms. The standard enthalpies of formation (ΔfH298), of the IMC in Al-Sc system assessed using experimental data of different authors, are the following (kJ/mol of atoms): Al3Sc: - 42.6; Al2Sc: - 47.8; AISc: - 51.1; AlSc2 - 41.0. The Cu-Sc intermetallides were investigated in the temperaturę rangę of 650-1050 K. Integral thermodynamic functions of IMC in Cu-Sc system can be presented as the following equations (kJ/mol of atoms): ΔfG (Cu4Sc) = - (23.1 ± 0.8) + (9.2 ± 1.0) º10-3T; ΔfG (Cu2Sc) = - (32.8 ± 1.0) + (14.5 š 1.2) º10-3T; ΔfG (CuSc) = - (35.5 ± 1.3) + (13.5 ±1.6) º10-3T.

PL

Metodą pomiaru siły elektromotorycznej ogniw galwanicznych wyznaczono cząstkowe energie swobodne tworzenia związków międzymetalicznych w układach Al-Sc, Cu-Sc I Pb-Sc w szerokim zakresie temperatur. Uzyskane wyniki posłużyły do wyznaczenia własności termodynamicznych badanych związków w 298.15 K. Energia swobodna tworzenia związku Pb5Sc6 ze stałego skandu i ciekłego ołowiu można na podstawie pomiarów SEM opisać równaniem (650-1040 K): ΔfG (Pb5Sc6) = - (49.60 ± 1.1) + (3.63 ± 1.3) º10-3 T, kJ/mol. Standardowe ciepło tworzenia (ΔfH298), związków międzymetalicznych w układzie Al-Sc zostało oszacowane na podstawie danych doświadczalnych pochodzących z różnych źródeł, jak następuje (kJ/mol): AI3SC: -42.6; Al2Sc: -47.8; AISc: -51.1; AlSc2: -41.0. Związki międzymetaliczne z układu Cu-Sc zbadano w przedziale temperatur 650 - 1050 K; ich własności termodynamiczne opisano następującymi równaniami (kJ/mol): ΔfG (Cu4Sc) = - (23.1 ± 0.8) + (9.2 ± 1.0) º10-3T; ΔfG (Cu2Sc) = - (32.8 ± 1.0) + (14.5 š 1.2) º10-3T; ΔfG (CuSc) = - (35.5 ± 1.3) + (13.5 ±1.6) º10-3T.

15

Calculation of the Au-Ge phase diagram for nanoparticles

63%

Eichhammer Y. , Roeck J. , Moelans N. , Iacopi F. , Blanpain B. , Heyns M.

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2008

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tom Vol. 53, iss. 4

1133-1139

EN

The CALPHAD (CALculation of PHAse Diagrams) method provides a powerful tool for the calculation of phase diagrams. It is based on thermodynamic databases gathering information on the relative stabilities of pure substances and mixing properties of alloys. We have added a size dependent contribution to an existing CALPHAD description of the Au-Ge bulk system. The parameters are optimized using composition and temperaturę dependent surface energies calculated according to the Butler model. The effect of particie size on the phase diagram is discussed for spherical nano-particles.

PL

Metoda CALPHAD jest doskonałym narzędziem do obliczania wykresów fazowych na podstawie danych termodynamicznych gromadzonych w różnych bazach danych. W pracy niniejszej dodano czynnik uwzględniający wielkość ziaren materiału do istniejącego opisu temodynamicznego układu Au-Ge. Parametry termodynamiczne zoptymalizowano stosując zależne od składu i temperatury energie powierzchniowe, wyliczone modelem Butlera. Rozpatrzono efekt wpływu rozmiaru cząstek na topologię wykresu fazowego zakładając kulisty kształt cząsteczek.

16

The theory of phase formation in rare earth metal systems

51%

Gschneidner K. A.

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2006

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tom Vol. 51, iss. 4

519-524

EN

The seventeen elements, which make up the rare earth family, consist of two non-4f - electron members, Sc and Y, and the fifteen 4 f electron containing lanthanide elements including La that has an empty localized 4f shell. In general, the physical properties, such as the metallic radii, electronegativities, melting points, and crystal structure sequence of the metallic elements, vary in a smooth and regular manner. By utilizing these systematic behaviors, we have learned a great deal about the chemical, metallurgical and physical behaviors of not only the rare earth elements, but also the other elements in the Periodic Table. This includes: (1) the dependence of the entropies of transformation and fusion of the pure metals on the structure and electronic nature; (2) the influence of lattice rigidity on solid solution formation and thus solved one of the oldest metallurgical riddles; (3) the representation of 91 binary rare earth diagrams by a single generalize phase diagram; and (4) the existence of 4f bonding in the lanthanide metals, alloys and compounds well before theorists confirmed this by first principle calculations.

PL

Na rodzine siedemnastu pierwiastków ziem rzadkich składają się dwa pierwiastki nie zawierające elektronów 4 f – Sc i Y, i piętnaście lantanowców w tym La, który posiada pustą zlokalizowaną podpowłokę 4 f . Można ogólnie stwierdzić, że własciwości tych metalicznych pierwiastków, takie jak promienie atomowe poszczególnych metali, elektroujemność, temperatury topnienia oraz sekwencja ich strukturkrystalicznych zmieniają się w sposób ciągły i regularny. Korzystając z tych systematycznych zachowań, poznano wiele właściwości chemicznych, metalurgicznych i fizycznych, nie tylko pierwiastków ziem rzadkich, lecz także innych pierwiastków układu okresowego. Dotyczy to w szczególności: (1) zależności entropii transformacji i entropii topnienia czystych metali od ich struktury krystalicznej i elektronowej, (2) wpływu rodzaju sieci krystalicznej na tworzenie roztworów stałych, które pozwala rozwiązać jedną z najstarszych metalurgicznych niejasności, (3) możliwości przedstawienia 91 wykresów pierwiastków ziem rzadkich za pomocą jednego ogólnego wykresu fazowego, (4) występowania wiązań 4 f w lantanowcach, ich stopach i związkach potwierdzonych następnie za pomocą teoretycznych obliczen ab initio.

17

Thermodynamic Properties of Cu-S Solutions

26%

Kucharski M.

|

nr 4