Alessandro di Afrodisia e Proclo sulla dialettica

Elenchos ◽  
2019 ◽  
Vol 40 (1) ◽  
pp. 165-197
Author(s):  
Davide Del Forno
Keyword(s):  
First Principles ◽  
Negative View ◽  
Alexander Of Aphrodisias ◽  
Logical Method ◽  
Specific Object ◽  
The Difference ◽  
Platonic Theology

AbstractIn this paper I compare Alexander of Aphrodisias’ and Proclus’ conceptions of dialectic by discussing a passage from Alexander’s commentary on Aristotle’s Topics and texts from Proclus’ Platonic Theology and commentary on Plato’s Parmenides. I show how Alexander takes up Aristotle’s view of dialectic as an argumentative technique that has no specific object but can be put in the service of philosophy e. g. to establish first principles. In a key passage, Alexander quotes some lines from the Parmenides to emphasize that this was also Plato’s view on dialectic. By contrast, Proclus uses the Parmenides as a crucial source for his conception of dialectic as the crowning glory of philosophy, and fiercely criticizes such interpretations of the Parmenides as that of Alexander, which reduce it to the illustration of a logical method. I argue that the difference in their conceptions of dialectic lies in Alexander’s positive and Proclus’ negative view on doxa and on its role in knowledge.

First-principles study of the difference in permittivity between Ba(Mg1 / 3Ta2 / 3)O3 and Ba(Mg1 / 3Nb2 / 3)O3

2009 ◽  
Vol 149 (19-20) ◽  
pp. 791-794 ◽  
Author(s):  
Yadong Dai ◽  
Guanghui Zhao ◽  
Liling Guo ◽  
Hanxing Liu
Keyword(s):  
First Principles ◽  
First Principles Study ◽  
The Difference

First-Principles Theory of Polarization in Ferroelectrics

1992 ◽  
Vol 291 ◽  
Author(s):  
R. Resta ◽  
M. Posternak ◽  
A. Baldereschi
Keyword(s):  
Spontaneous Polarization ◽  
First Principles ◽  
Ferroelectric Materials ◽  
Recent Experimental Data ◽  
Modern Theory ◽  
Rigid Core ◽  
Novel Approach ◽  
Prototype Structure ◽  
Effective Charges ◽  
The Difference

ABSTRACTWe outline a modern theory of the spontaneous polarization P in pyroelectric and ferroelectric materials. Although P itself isnot an observable, the difference ΔP between two crystal states can indeed be measured and calculated. We define P as the difference between the polar structure and a suitably chosen nonpolar prototype structure. We previously proposed and implemented a supercell scheme in order to evaluate P in pyroelectric BeO; here we adopt an approach recently developed by King-Smith and Vanderbilt, where ΔP is obtained from the computation of Berry's phases, with no use of supercells. We apply this novel approach, which is numerically very convenient, in order to revisit our previous work on BeO. We then perform a first-principles investigation of the spontaneous polarization P of KNbO3 in its tetragonal phase, which is a well studied perovskite ferroelectric. Our calculated P value confirms the most recent experimental data. The polarization is linear in the ferroelectric distortion; the Born effective charges show strong variations from nominal ionic values, and a large inequivalence of the 0 ions. Only the highest nine valence-band states (O 2p) contribute to P, while all the other states behave as rigid core states.

scholarly journals LOGIC OF RELATIVITY

2021 ◽  
pp. 42-52
Author(s):  
Ihor Ohirko ◽  
Zinovii Partyko
Keyword(s):  
Modal Logic ◽  
Symbolic Logic ◽  
Logical Theory ◽  
Relative Truth ◽  
Time Space ◽  
Different Types ◽  
Logical Method ◽  
Standard Values ◽  
The Difference ◽  
Modal Values

The problem of the truth of statements is considered. This study had the goal to develop a logical theory that would allow considering the context (the paradigm) from which would depend on the truth of the statement. For the development of such a theory, called the logic of relativity, the following methods of research are used as abstraction, analysis (traditional), synthesis, deduction, formalisation, axiomatisation, logical method. In order to develop the logic of relativity, it is expedient to use the achievements in the area of situational logic. Under the situation, it is proposed to understand two circumstances (time and space) and a condition that creates a context (paradigm) statement. Specifies the modal values that these three parameters can acquire and examines different types of situations. In order to write statements in the logic of relativity, a form of the statement of statements is proposed in the language of extended symbolic logic. For the theory of the logic of relativity, a set of four axioms is proposed and a series of laws. In particular, it is indicated that the values of the assertions in the logic of relativity are the following five estimates: truth, relative truth, relative is absurd, unclear, uncertain. Some theorems of the logic of relativity are proposed. A number of examples of texts in the natural language are given to interpret the statements of the logic of relativity. It is indicated that the proposed apparatus of the logic of relativity should be regarded as a kind of modal logic. The difference in the logic of relativity from situational logic is that it considers the factor of movement (motion) of statements in time, space and environment conditions, which was not considered by situational logic. The logic of relativity should be used wherever it is necessary to take into account the possibility of moving allegations regarding time, space and environment of conditions. One of the most important conclusions of the study is that in the logic to the standard values of truth (true, probably true, false, uncertain), it is expedient to add another value: relatively true (and accordingly: relatively false).

Electron-Phonon Coupling Strength of Specific Phonons from First Principles Lapw Calculations

1988 ◽  
Vol 141 ◽  
Author(s):  
H. Krakauer ◽  
R. E. Cohen ◽  
W. E. Pickett
Keyword(s):  
Coupling Strength ◽  
First Principles ◽  
Mode Coupling ◽  
Local Density ◽  
Matrix Elements ◽  
Dual Representation ◽  
Electron Phonon Interaction ◽  
Electron Phonon Coupling ◽  
Coupling Strengths ◽  
The Difference

AbstractElectron-phonon matrix elements, phonon linewidths and mode coupling strengths are being calculated for La2-xMxCuO4 (M-divalent cation, for paramagnetic x-0.0 and for x-0.15 in a rigid band picture) from first principles local density calculations. The change in potential due to a particular phonon mode is calculated from the difference of self-consistent one-electron potentials, and appropriate Fermi surface averages are carried out for selected modes, allowing us to obtain the phonon linewidth due to the electron-phonon interaction, and the corresponding coupling strength λQ. Here we establish the numerical accuracy within the dual representation of the potential used in the Linearized Augmented Plane Wave (LAPW) method. Evaluations of phonon linewidths and mode coupling strengths are presented for Al and Nb and compared with previous information on these modes. We present preliminary results for the full matrix elements and coupling of the La2CuO4 oxygen planar X-point breathing mode, and compare with a simpler approximation.

First-Principles Study of Nanofacet Formation on 4H-SiC(0001) Surface

2014 ◽  
Vol 778-780 ◽  
pp. 201-205
Author(s):  
Keisuke Sawada ◽  
Jun Ichi Iwata ◽  
Atsushi Oshiyama
Keyword(s):  
Surface Energy ◽  
Total Energy ◽  
First Principles ◽  
Atomic Layer ◽  
First Principles Calculations ◽  
Atomic Structures ◽  
First Principles Study ◽  
Energy Variation ◽  
The Difference ◽  
Facet Formation

We perform the first-principles calculations on the 4H-SiC(0001) surface and clarify the mechanism of the facet formation. We first identify atomic structures of single-, double- and quadribilayer steps and find that the single-bilayer (SB) step has the lowest total energy among these three step structures. Then, we reveal that the nanofacet consisting of SB steps is more energetically stable than the equally spaced SB step and the surface-energy variation caused by the difference of stacking sequences of the bi-atomic layer near the surface is an important factor of the facet formation.

Calculation of electronic structure and mechanical properties of DO3–Fe75-xSi25Nix intermetallic compounds by first principles

2015 ◽  
Vol 29 (13) ◽  
pp. 1550087
Author(s):  
R. Ma ◽  
M. P. Wan ◽  
J. Huang ◽  
Q. Xie
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elastic Parameters ◽  
Functional Theory ◽  
Ni Content ◽  
The Density Functional Theory ◽  
The Difference

Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to investigate the electronic structures and mechanical properties of DO 3– Fe 75-x Si 25 Ni x(x = 0, 3.125, 6.25 and 9.375) intermetallic compounds. The elastic parameters were calculated, and then the bulk modulus, shear modulus and elastic modulus were derived. The paper then focuses on the discussion of ductility and plasticity. The results show that by adding appropriate Ni to Fe 3 Si intermetallic compound can improve the ductility. But the hardness will increase when the Ni content exceeds 6.25%. Analysis of density of states (DOS) and overlap populations indicates that with the difference of the strength of bonding and activity, there were some differences of ductility among different Ni contents. The Fe 71.875 Ni 3.125 Si 25 has the lowest hardness because the covalent bonding (Fe–Si bond and Si–Ni bond) has the minimum covalent electrons.

First-Principles Study on Elastic Anomalies in Ag/Al Multilayers

2007 ◽  
Vol 345-346 ◽  
pp. 959-962
Author(s):  
Yusuke Kinoshita ◽  
Yoshitaka Umeno ◽  
Takayuki Kitamura
Keyword(s):  
Electronic Structure ◽  
Elastic Constant ◽  
First Principles ◽  
Electronic Structures ◽  
Interplanar Spacing ◽  
First Principles Calculation ◽  
Mixing Rule ◽  
Modulation Period ◽  
The Difference ◽  
Elastic Anomalies

Using the first-principles calculation, the elastic constant C44 of Ag/Al multilayers with different modulation periods from 0.43 nm to 2.27 nm has been evaluated in order to examine the effect of atomic and electronic structures on it. With increasing modulation period, C44 decreases and becomes close to that obtained by the conventional mixing rule, however, the difference of 8 % still remains at the modulation period of 2.27 nm. As C44 correlates with the average interplanar spacing, the decrease of C44 can be explained by the decrease of the charge density in the stacking direction due to the increase of the average interplanar spacing. The difference in the electronic structure is included in the effect of atomic structure.

scholarly journals Manifestation of axion electrodynamics through magnetic ordering on edges of a topological insulator

2015 ◽  
Vol 112 (37) ◽  
pp. 11514-11518 ◽  
Author(s):  
Yea-Lee Lee ◽  
Hee Chul Park ◽  
Jisoon Ihm ◽  
Young-Woo Son
Keyword(s):  
Electric Field ◽  
Topological Insulator ◽  
Time Reversal ◽  
First Principles ◽  
Surface States ◽  
Magnetic Ordering ◽  
Crystal Face ◽  
Magnetic Dipoles ◽  
Topological Surface ◽  
The Difference

Because topological surface states of a single-crystal topological insulator can exist on all surfaces with different crystal orientations enclosing the crystal, mutual interactions among those states contiguous to each other through edges can lead to unique phenomena inconceivable in normal insulators. Here we show, based on a first-principles approach, that the difference in the work function between adjacent surfaces with different crystal-face orientations generates a built-in electric field around facet edges of a prototypical topological insulator such as Bi2Se3. Owing to the topological magnetoelectric coupling for a given broken time-reversal symmetry in the crystal, the electric field, in turn, forces effective magnetic dipoles to accumulate along the edges, realizing the facet-edge magnetic ordering. We demonstrate that the predicted magnetic ordering is in fact a manifestation of the axion electrodynamics in real solids.

Tuned Tilt of Epitaxial Crystals

MRS Bulletin ◽  
1991 ◽  
Vol 16 (6) ◽  
pp. 30-33 ◽  
Author(s):  
C.P. Flynn
Keyword(s):  
Tilt Angle ◽  
First Principles ◽  
Growth Process ◽  
Molecular Beam ◽  
Interfacial Structure ◽  
Tilt Axis ◽  
Atomic Spacing ◽  
The Difference ◽  
Lattice Planes ◽  
Lattice Solid

At first sight it may seem self-evident that epitaxial crystals must grow with their atomic planes parallel to the lattice planes of the substrate crystal. The simplified sketch in Figure 1a shows atoms raining onto a substrate from a molecular beam, and then diffusing to step-edges in a desirably controlled growth process termed step-edge (or ledge) flow. Drawn this way, the conclusion that the planes must lie parallel seems obvious. If, however, the process is heteroepitaxial, and the new lattice (solid circles) differs in spacing or structure from the substrate template (lines), the outcome is less straight-forward. Accommodating the difference of step heights at the interface then requires local tilts amounting to a fraction of one atomic spacing in, say, 25 atoms or perhaps half a degree, depending from one point to the next on details of the neighboring interfacial structure.In what follows I describe a qualitatively different and newly discovered behavior we term coherent tilt. The coherent tilt process causes the atomic planes of the epilayer to grow at an accurately predictable and reproducible angle with respect to the substrate planes. The tilt axis, tilt angle, and sense of rotation remain precisely fixed over an entire substrate, with the result that the process occurs coherently over the dimensions of a macroscopic sample. Large tilts over 7° have already been produced with the angle predictable from first principles to 0.1° The characteristics of coherent tilt are sketched in Figure 1b.

scholarly journals Theoretical investigations of hydrogen absorption in the A15 intermetallics Ti3Sb and Ti3Ir

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Gordon J. Miller ◽  
Ranuri S. Dissanayaka Mudiyanselage ◽  
Weiwei Xie
Keyword(s):  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Hydrogen Atoms ◽  
Metal Metal ◽  
Theoretical Investigations ◽  
Densities Of States ◽  
The Difference ◽  
Structure Calculations ◽  
Hydrogen Insertion

Abstract Ti3Sb and Ti3Ir adopt the A15 (Cr3Si type) structure and are reported to incorporate hydrogen atoms to an extent, respectively, of Ti3SbH∼3 and Ti3IrH3.8. First-principles electronic structure calculations were performed to identify factors contributing to the difference in maximum hydrogen composition for these two intermetallic compounds. Relative energies and changes in energy densities of states and crystal orbital Hamilton populations upon H insertion in the intermetallic compounds were examined. In both compounds, hydrogen atoms are attracted to [Ti4] tetrahedral interstitial sites over any others. The natures of metal-hydrogen and metalloid-hydrogen bonding and the effects of hydrogen insertion on metal-metal and metal-metalloid bonding have an influence on the maximum hydrogen contents for Ti3Sb and Ti3Ir.

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