Pub Date : 2002-07-01DOI: 10.1080/13642810208223154
P. Mohanty, S. Ram
Abstract Eu2O3 in divided groups in pores in a mesoporous Al2O3 (amorphous) has a confined growth in nanocrystals (average, 30 nm diameter) in a new polymorph of R3c hexagonal crystal structure with lattice parameters a = 0.5468 nm and c = 1.6950 nm. This occurs on reacting dispersed Eu3+ cations (in water) with a mesoporous AlO(OH) · α2O powder. A pore incorporates Eu3+ cations in a confined group depending on its size and governs controlled Eu2O3 nucleation and growth in a self-confined dimension in a nanocrystal. This new lattice involves a 5.60, 2.99 and 1.03 times larger volume V 0, enclosed in a reduced S 0 = 5.41 nm2 surface per unit volume relative to 9.27, 9.28 and 5.52 nm2, in the bulk hexagonal Eu2O3, monoclinic Eu2O3 and cubic Eu2O3 polymorphs respectively. From the pressure–volume isotherm, the large V 0 implies that it grows quickly under the influence of a reduced effective pressure in the pores so that it balances the ▵P → 0 pressure gradient as early as possible. The results are discussed with a proposed model of nucleation and growth in a self-confined dimension under the influence of a reduced pressure.
{"title":"Confined growth of Eu2O3 nanocrystals in a new polymorph in amorphous mesoporous Al2O3","authors":"P. Mohanty, S. Ram","doi":"10.1080/13642810208223154","DOIUrl":"https://doi.org/10.1080/13642810208223154","url":null,"abstract":"Abstract Eu2O3 in divided groups in pores in a mesoporous Al2O3 (amorphous) has a confined growth in nanocrystals (average, 30 nm diameter) in a new polymorph of R3c hexagonal crystal structure with lattice parameters a = 0.5468 nm and c = 1.6950 nm. This occurs on reacting dispersed Eu3+ cations (in water) with a mesoporous AlO(OH) · α2O powder. A pore incorporates Eu3+ cations in a confined group depending on its size and governs controlled Eu2O3 nucleation and growth in a self-confined dimension in a nanocrystal. This new lattice involves a 5.60, 2.99 and 1.03 times larger volume V 0, enclosed in a reduced S 0 = 5.41 nm2 surface per unit volume relative to 9.27, 9.28 and 5.52 nm2, in the bulk hexagonal Eu2O3, monoclinic Eu2O3 and cubic Eu2O3 polymorphs respectively. From the pressure–volume isotherm, the large V 0 implies that it grows quickly under the influence of a reduced effective pressure in the pores so that it balances the ▵P → 0 pressure gradient as early as possible. The results are discussed with a proposed model of nucleation and growth in a self-confined dimension under the influence of a reduced pressure.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81196833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-07-01DOI: 10.1080/13642810208223162
A. Hadjadj, B. Equer, A. Beorchia, P. Cabarrocas
Abstract The Kelvin probe technique can be used as a very accurate tool to measure contact potential differences (CPDs). However, the experimentally observed CPD dependence on the probe-sample distance, the so-called stray capacitance effect, is a parasitic effect not explained in the simple Kelvin probe theory. It can be especially disturbing when using a local Kelvin probe or Kelvin probe microscopy as it hinders quantitative use of CPD measurements. We show that this effect can be described without the expedient of stray capacitors by taking into account the electrostatic induction of metal objects located in the vicinity of the probe-sample system. This model leads to excellent agreement with the experimental variations in the apparent value of CPD with the probe-sample distance and allows us to recover the exact CPD value.
{"title":"Contact potential measurements with a local Kelvin probe","authors":"A. Hadjadj, B. Equer, A. Beorchia, P. Cabarrocas","doi":"10.1080/13642810208223162","DOIUrl":"https://doi.org/10.1080/13642810208223162","url":null,"abstract":"Abstract The Kelvin probe technique can be used as a very accurate tool to measure contact potential differences (CPDs). However, the experimentally observed CPD dependence on the probe-sample distance, the so-called stray capacitance effect, is a parasitic effect not explained in the simple Kelvin probe theory. It can be especially disturbing when using a local Kelvin probe or Kelvin probe microscopy as it hinders quantitative use of CPD measurements. We show that this effect can be described without the expedient of stray capacitors by taking into account the electrostatic induction of metal objects located in the vicinity of the probe-sample system. This model leads to excellent agreement with the experimental variations in the apparent value of CPD with the probe-sample distance and allows us to recover the exact CPD value.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78512046","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-07-01DOI: 10.1080/13642810208223160
L. Ben Hassine, J. Auchet, J. Gasser
Abstract We present our new accurate measurements on the electrical resistivity and thermopower of liquid gallium as a function of temperature. To interpret our experimental data we used, for the first time to our knowledge (earlier calculations used the pseudopotential formalism), ab initio calculations of the electrical resistivity ρ(E) and of the thermoelectric power Q(E) of liquid gallium as functions of energy. This formalism has the great advantage of including a full-energy dependent calculation of the thermopower. To construct the phase shifts we used the experimental pair correlation function. To calculate the resistivity and thermopower we used both the structure factor obtained experimentally and that calculated with hard spheres. The results are compared and discussed. Various potentials based on the Hartree-Fock formalism and using different exchange contributions have been used. Overall agreement between calculation and experiment is obtained. It seems, however, that the Kohn-Sham value of the X-α Slater approximation gives results closer to experiment than the Slater value for both resistivity and thermopower. Subsequently, the problem of the sign of the thermopower of liquid metals is discussed and explained.
{"title":"Electrical resistivity and thermoelectric power of molten gallium: Theory versus experiment","authors":"L. Ben Hassine, J. Auchet, J. Gasser","doi":"10.1080/13642810208223160","DOIUrl":"https://doi.org/10.1080/13642810208223160","url":null,"abstract":"Abstract We present our new accurate measurements on the electrical resistivity and thermopower of liquid gallium as a function of temperature. To interpret our experimental data we used, for the first time to our knowledge (earlier calculations used the pseudopotential formalism), ab initio calculations of the electrical resistivity ρ(E) and of the thermoelectric power Q(E) of liquid gallium as functions of energy. This formalism has the great advantage of including a full-energy dependent calculation of the thermopower. To construct the phase shifts we used the experimental pair correlation function. To calculate the resistivity and thermopower we used both the structure factor obtained experimentally and that calculated with hard spheres. The results are compared and discussed. Various potentials based on the Hartree-Fock formalism and using different exchange contributions have been used. Overall agreement between calculation and experiment is obtained. It seems, however, that the Kohn-Sham value of the X-α Slater approximation gives results closer to experiment than the Slater value for both resistivity and thermopower. Subsequently, the problem of the sign of the thermopower of liquid metals is discussed and explained.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84998969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-17DOI: 10.1080/13642810208223166
A. Balatsky, Y. Manassen, R. Salem
Abstract Electron spin resonance-scanning tunnelling microscopy is an emerging technique which is capable of detecting the precession of a single spin. We discuss a mechanism based on direct exchange coupling between the tunnelling electrons and the local precessing spin S. We claim that, since the number of tunnelling electrons in a single precessing period is small (about 20), one may expect a net temporary polarization within this period which will couple via exchange interaction to the localized spin. This coupling will modulate the tunnelling barrier with the Larmor frequency of the precessing spin ωL. This modulation, although randomly changing from cycle to cycle, will produce an elevated noise in the current at ωL. We find that for relevant values of parameters the signal-to-noise ratio in the spectral characteristic is 2–4 and is comparable with the values of the signal-to-noise ratio reported by Manassen and co-workers and by Durkan and Welland. The magnitude of the current fluctuation is a relatively weak increasing function of the dc and the magnetic field. The linewidth produced by the back action effect of tunnelling electrons on the precessing spin is also discussed.
{"title":"Exchange-based noise spectroscopy of a single precessing spin with scanning tunnelling microscopy","authors":"A. Balatsky, Y. Manassen, R. Salem","doi":"10.1080/13642810208223166","DOIUrl":"https://doi.org/10.1080/13642810208223166","url":null,"abstract":"Abstract Electron spin resonance-scanning tunnelling microscopy is an emerging technique which is capable of detecting the precession of a single spin. We discuss a mechanism based on direct exchange coupling between the tunnelling electrons and the local precessing spin S. We claim that, since the number of tunnelling electrons in a single precessing period is small (about 20), one may expect a net temporary polarization within this period which will couple via exchange interaction to the localized spin. This coupling will modulate the tunnelling barrier with the Larmor frequency of the precessing spin ωL. This modulation, although randomly changing from cycle to cycle, will produce an elevated noise in the current at ωL. We find that for relevant values of parameters the signal-to-noise ratio in the spectral characteristic is 2–4 and is comparable with the values of the signal-to-noise ratio reported by Manassen and co-workers and by Durkan and Welland. The magnitude of the current fluctuation is a relatively weak increasing function of the dc and the magnetic field. The linewidth produced by the back action effect of tunnelling electrons on the precessing spin is also discussed.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79923445","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-01DOI: 10.1080/13642810208218358
C. Edgcombe
Abstract The theory for field emission from a smooth cold metallic surface has been developed to describe emission from a spherical cap. The potential distribution in the barrier region, image potential and transmission function are modified from their planar equivalents. The change in transmission modifies the pre-exponential term in the current density. An effective solid angle is defined so that the variation in emission over the surface is taken into account without requiring knowledge of the apex radius. These modifications have been used in comparing the current-voltage characteristics measured on a single carbon tip made as described in part I with values calculated using the known dimensions of the tip. The field at the surface, required for consistency with the known work function, is found to exceed the calculated field by a factor of about 2.6. This could be caused by roughness of deposition on the atomic scale. An estimate of the radius of the emitting surface can be obtained by using both the slope and the intercept of a plot of 1n(I) against (anode voltage)−1.
{"title":"Experimental and computational study of field emission characteristics from amorphous carbon single nanotips grown by carbon contamination II. Theory","authors":"C. Edgcombe","doi":"10.1080/13642810208218358","DOIUrl":"https://doi.org/10.1080/13642810208218358","url":null,"abstract":"Abstract The theory for field emission from a smooth cold metallic surface has been developed to describe emission from a spherical cap. The potential distribution in the barrier region, image potential and transmission function are modified from their planar equivalents. The change in transmission modifies the pre-exponential term in the current density. An effective solid angle is defined so that the variation in emission over the surface is taken into account without requiring knowledge of the apex radius. These modifications have been used in comparing the current-voltage characteristics measured on a single carbon tip made as described in part I with values calculated using the known dimensions of the tip. The field at the surface, required for consistency with the known work function, is found to exceed the calculated field by a factor of about 2.6. This could be caused by roughness of deposition on the atomic scale. An estimate of the radius of the emitting surface can be obtained by using both the slope and the intercept of a plot of 1n(I) against (anode voltage)−1.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85902822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-01DOI: 10.1080/13642810208218359
P. Weinberger, V. Drchal, J. Kudrnovský, I. Turek, H. Herper, L. Szunyogh, C. Sommers
Abstract Tunnelling between two semi-infinite ferromagnetic electrodes separated by vacuum is studied theoretically on an ab-initio level by using the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker and the spin-polarized non-relativistic tight-binding linear muffin-tin orbital method. The Kubo-Greenwood equation is employed to calculate the non-local conductivity and layer-resolved sheet resistances; the transmission matrix formulation in turn is used to evaluate the conductance. We show that the dependence of sheet resistance on the imaginary part of the Fermi energy allows us to distinguish between the tunnelling and conductive regimes of electron transport. Our numerical studies of the system bcc Fe(100)/vacuum/bcc Fe(100) show quite dramatic variations in the electrostatic potential in the vacuum region and a gradual development of the tunnelling barrier with increasing thickness of the vacuum barrier. Varying the Madelung potential in the interior of the vacuum barrier allowed us to simulate spacers made of semiconducting or insulating material and to discuss the conditions for the presence of a magnetoresistance in such multilayers. As far as the thickness of the vacuum barrier is concerned the results obtained with the transmission matrix approach for fee Co(001)/vacuum/fee Co(001) show a similar tendency to those obtained within the Kubo-Greenwood equation for bcc Fe(100)/vacuum/bcc Fe(100); asymptotically, that is with increasing thickness of the vacuum barrier, the magnetoresistance tends to zero.
{"title":"Aspects of magnetotunnelling drawn from ab-initio-type calculations","authors":"P. Weinberger, V. Drchal, J. Kudrnovský, I. Turek, H. Herper, L. Szunyogh, C. Sommers","doi":"10.1080/13642810208218359","DOIUrl":"https://doi.org/10.1080/13642810208218359","url":null,"abstract":"Abstract Tunnelling between two semi-infinite ferromagnetic electrodes separated by vacuum is studied theoretically on an ab-initio level by using the fully relativistic spin-polarized screened Korringa-Kohn-Rostoker and the spin-polarized non-relativistic tight-binding linear muffin-tin orbital method. The Kubo-Greenwood equation is employed to calculate the non-local conductivity and layer-resolved sheet resistances; the transmission matrix formulation in turn is used to evaluate the conductance. We show that the dependence of sheet resistance on the imaginary part of the Fermi energy allows us to distinguish between the tunnelling and conductive regimes of electron transport. Our numerical studies of the system bcc Fe(100)/vacuum/bcc Fe(100) show quite dramatic variations in the electrostatic potential in the vacuum region and a gradual development of the tunnelling barrier with increasing thickness of the vacuum barrier. Varying the Madelung potential in the interior of the vacuum barrier allowed us to simulate spacers made of semiconducting or insulating material and to discuss the conditions for the presence of a magnetoresistance in such multilayers. As far as the thickness of the vacuum barrier is concerned the results obtained with the transmission matrix approach for fee Co(001)/vacuum/fee Co(001) show a similar tendency to those obtained within the Kubo-Greenwood equation for bcc Fe(100)/vacuum/bcc Fe(100); asymptotically, that is with increasing thickness of the vacuum barrier, the magnetoresistance tends to zero.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73281351","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-01DOI: 10.1080/13642810208218360
V. Leppert, A. Murali, S. Risbud, M. Stender, P. Power, C. Nelson, P. Banerjee, A. Mayes
Abstract The objective of this work was to produce an ordered array of size-controlled gallium nitride (GaN) nanoparticles. The synthesis was performed by the in situ formulation and subsequent decomposition of cyclotrigallazane in a polystyrene (PS)-b-poly(4-vinylpyridine) (b-P4VP) block copolymer matrix. The matrix served as a templating medium to constrain the particle size and to allow the control of particle morphology, spacing and packing arrangement. The size and spacing of nanoparticles were controlled by the molecular weight of the entire polymer chain (81 000g mol−1), and the particle morphology and packing arrangement were controlled by the ratio of the sequestering block to the matrix block (21 wt% P4VP to 79 wt% PS by elemental analysis). High-resolution and analytical transmission electron microscopy revealed the amorphous nanoparticles to be composed mainly of gallium and nitrogen (with oxygen detected in some particles) about 10nm in diameter with an average interparticle distance of 60 nm and organized in a regular hexagonal packing arrangement. The impact of this synthesis technique is to afford the means to investigate systematically the effect of quantum confinement and quantum coupling on the optical properties of small GaN particles.
{"title":"High-resolution electron microscopy and microanalysis of ordered arrays of size-controlled amorphous gallium nitride nanoparticles synthesized in situ in a block copolymer matrix","authors":"V. Leppert, A. Murali, S. Risbud, M. Stender, P. Power, C. Nelson, P. Banerjee, A. Mayes","doi":"10.1080/13642810208218360","DOIUrl":"https://doi.org/10.1080/13642810208218360","url":null,"abstract":"Abstract The objective of this work was to produce an ordered array of size-controlled gallium nitride (GaN) nanoparticles. The synthesis was performed by the in situ formulation and subsequent decomposition of cyclotrigallazane in a polystyrene (PS)-b-poly(4-vinylpyridine) (b-P4VP) block copolymer matrix. The matrix served as a templating medium to constrain the particle size and to allow the control of particle morphology, spacing and packing arrangement. The size and spacing of nanoparticles were controlled by the molecular weight of the entire polymer chain (81 000g mol−1), and the particle morphology and packing arrangement were controlled by the ratio of the sequestering block to the matrix block (21 wt% P4VP to 79 wt% PS by elemental analysis). High-resolution and analytical transmission electron microscopy revealed the amorphous nanoparticles to be composed mainly of gallium and nitrogen (with oxygen detected in some particles) about 10nm in diameter with an average interparticle distance of 60 nm and organized in a regular hexagonal packing arrangement. The impact of this synthesis technique is to afford the means to investigate systematically the effect of quantum confinement and quantum coupling on the optical properties of small GaN particles.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91185545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-01DOI: 10.1080/13642810208218357
C. Edgcombe, U. Valdré
Abstract Some properties of electron field emitters based on various types of carbon are difficult to measure and are not well known. This is particularly true for amorphous carbon films, for nanotubes and for nanotips grown by carbon contamination in a scanning electron microscope. We show that by combining together experimental data (i.e. emitter geometry from electron microscopy observations, and field emission current and applied voltage measurements), numerically computed values of the electric field at the tip surface and the Fowler-Nordheim (F-N) equation, it is possible to estimate values of parameters such as the work function, the enhancement factor, the tip radius and the effective emitting area. The general applicability of this approach and corresponding results are emphasized. We also show that, when the experimental parameters that are known are superfluous in number (i.e. more than the minimum number needed), a discrepancy exists, firstly, between the value of the emitter radius worked out through the F-N equation and that derived from electron microscopy and, secondly, between the calculated work function and that independently obtained by Kelvin probe microscopy. Possible reasons for these discrepancies are put forward and discussed.
{"title":"Experimental and computational study of field emission characteristics from amorphous carbon single nanotips grown by carbon contamination. I. Experiments and computation","authors":"C. Edgcombe, U. Valdré","doi":"10.1080/13642810208218357","DOIUrl":"https://doi.org/10.1080/13642810208218357","url":null,"abstract":"Abstract Some properties of electron field emitters based on various types of carbon are difficult to measure and are not well known. This is particularly true for amorphous carbon films, for nanotubes and for nanotips grown by carbon contamination in a scanning electron microscope. We show that by combining together experimental data (i.e. emitter geometry from electron microscopy observations, and field emission current and applied voltage measurements), numerically computed values of the electric field at the tip surface and the Fowler-Nordheim (F-N) equation, it is possible to estimate values of parameters such as the work function, the enhancement factor, the tip radius and the effective emitting area. The general applicability of this approach and corresponding results are emphasized. We also show that, when the experimental parameters that are known are superfluous in number (i.e. more than the minimum number needed), a discrepancy exists, firstly, between the value of the emitter radius worked out through the F-N equation and that derived from electron microscopy and, secondly, between the calculated work function and that independently obtained by Kelvin probe microscopy. Possible reasons for these discrepancies are put forward and discussed.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76862452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-01DOI: 10.1080/13642810208218361
J. Dow, D. R. Harshman
Abstract The superconducting hole condensate resides in the SrO planes, or in the BaO planes, or in the interstitial regions of high-temperature perovskite superconductors, depending upon the crystal structure. Supporting evidence includes the following: firstly, PrBa2Cu3O7 superconducts in its BaO layers, and not in its cuprate planes; secondly, the similarity of the layer charges for YBa2Cu3Ox and PrBa2Cu3Ox indicates that both materials superconduct in their BaO layers; thirdly, Gd2-zCezSr2Cu2TiO10, Pr2-zCezSr2Cu2NbO10 and Eu2-zCezSr2Cu2TiO10 all superconduct in their SrO layers, and not in their cuprate planes; and fourthly, the superconducting hole condensate for Cu-doped Sr2YRuO6 (a material with no cuprate planes to better than 1%) must reside in its SrO layers.
{"title":"Explanation of high-temperature superconductivity without cuprate planes","authors":"J. Dow, D. R. Harshman","doi":"10.1080/13642810208218361","DOIUrl":"https://doi.org/10.1080/13642810208218361","url":null,"abstract":"Abstract The superconducting hole condensate resides in the SrO planes, or in the BaO planes, or in the interstitial regions of high-temperature perovskite superconductors, depending upon the crystal structure. Supporting evidence includes the following: firstly, PrBa2Cu3O7 superconducts in its BaO layers, and not in its cuprate planes; secondly, the similarity of the layer charges for YBa2Cu3Ox and PrBa2Cu3Ox indicates that both materials superconduct in their BaO layers; thirdly, Gd2-zCezSr2Cu2TiO10, Pr2-zCezSr2Cu2NbO10 and Eu2-zCezSr2Cu2TiO10 all superconduct in their SrO layers, and not in their cuprate planes; and fourthly, the superconducting hole condensate for Cu-doped Sr2YRuO6 (a material with no cuprate planes to better than 1%) must reside in its SrO layers.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82927725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2002-06-01DOI: 10.1080/13642810208218362
C. Colinet, A. Pasturel
Abstract The relative stabilities of L12, D022, D023 and several one-dimensional (1D) long period structures (LPSs) in the Cu3Pd intermetallic compound are investigated employing the Vienna ab initio simulation package. The energy effects due to the tetragonal distortion of the D022 and D023 structures and other 1D LPSs are small, and those due to the cell internal displacements of the atoms in the LPSs are negligible. With distortion, the <3> structure is found to be the ground state; however, the structures <4> and <43> are rather close in energy to this ground state. The energy results are discussed in the framework of the axial next-nearest-neighbour Ising model. Predictions of the energy differences between series of 1D LPSs and the L12 structure are provided. The (001) antiphase boundary energy is also determined using the same model.
{"title":"Ab initio calculation of the stability of one-dimensional long-period structures in the Cu3Pd compound","authors":"C. Colinet, A. Pasturel","doi":"10.1080/13642810208218362","DOIUrl":"https://doi.org/10.1080/13642810208218362","url":null,"abstract":"Abstract The relative stabilities of L12, D022, D023 and several one-dimensional (1D) long period structures (LPSs) in the Cu3Pd intermetallic compound are investigated employing the Vienna ab initio simulation package. The energy effects due to the tetragonal distortion of the D022 and D023 structures and other 1D LPSs are small, and those due to the cell internal displacements of the atoms in the LPSs are negligible. With distortion, the <3> structure is found to be the ground state; however, the structures <4> and <43> are rather close in energy to this ground state. The energy results are discussed in the framework of the axial next-nearest-neighbour Ising model. Predictions of the energy differences between series of 1D LPSs and the L12 structure are provided. The (001) antiphase boundary energy is also determined using the same model.","PeriodicalId":20016,"journal":{"name":"Philosophical Magazine Part B","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2002-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78941147","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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