• Title/Summary/Keyword: first-principles

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Computational Simulations of Thermoelectric Transport Properties

  • Ryu, Byungki;Oh, Min-Wook
    • Journal of the Korean Ceramic Society
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    • v.53 no.3
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    • pp.273-281
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    • 2016
  • This review examines computational simulations of thermoelectric properties, such as electrical conductivity, Seebeck coefficient, and thermal conductivity. With increasing computing power and the development of several efficient simulation codes for electronic structure and transport properties calculations, we can evaluate all the thermoelectric properties within the first-principles calculations with the relaxation time approximation. This review presents the basic principles of electrical and thermal transport equations and how they evaluate properties from the first-principles calculations. As a model case, this review presents results on $Bi_2Te_3$ and Si. Even though there is still an unsolved parameter such as the relaxation time, the effectiveness of the computational simulations on the transport properties will provide much help to experimental scientist researching novel thermoelectric materials.

A Study on Family Ethic of Buddhism (종교의 가정윤리에 관한연구)

  • 서병숙
    • Journal of Families and Better Life
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    • v.11 no.2
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    • pp.111-120
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    • 1993
  • The purpose of the study is to find how the family moral principles are placed in the Buddhist Sutra how they come up to the surface through certain course. We set up the following five kinds of question for aim of this study First in which form are the family moral principles placed in the Buddhist Sutra ? That is are they shown devided into two between the fundamental though of Buddhism and the concrete description? Second how are the family moral principles melted into the fundamental though of Bud-dhism ? Buddhism takes a cognitive method of pursuiting one from divesification,. If that is so the family moral principles will establish the fundamental thought of Buddhism melted along with other phenomena. When the fundamental thought of Buddhism is restored to the family moral principles which image are they presented with us? Third if the family moral princprinciples melted into the fundamental thought of Buddhism in itself came up to the surface ? Buddhism has a and is mixed together. The family moral principles of Buddhism are named from the fundamental thoughts to the family moral principles and do not come up to the surface but are melted into the important concepts of Buddism that is charity kama nirvara emptiness the principle of middle way. The aspects of the family moral principles which are melted into theses thoughts: 1) The concept of loving-kindness including equality non-self practice is shown in the family moral principles. 2) The thought of karma includes the moral principles for interdependence between the building up of home and family members. 3) Home should be a place of self-realization from the suffering realization This kind of home salvation should be set up by family members themselves and the consciousness of the master that such salvation is neither to be made by others not to be given by god is presented one should be the master of one's life 4) The thought of emptiness includes the social extension of home and those of the moral principles of collective body of family. 5) The Buddnist family is morality is based on the principle of the middle way shich means neither too extrim nor lacking.

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A First Principles Calculation of the Coherent Interface Energies between Group IV Transition Metal Nitrides and bcc Iron (IV족 천이금속 질화물과 bcc Fe간 계면 에너지의 제일원리 연구)

  • Chung, Soon-Hyo;Jung, Woo-Sang;Byun, Ji-Young
    • Korean Journal of Materials Research
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    • v.16 no.8
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    • pp.473-478
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    • 2006
  • The coherent interface energies and misfit strain energies of Fe/XN (X=Ti, Zr, Hf) systems were calculated by first principles method. The interface energies in Fe/TiN, Fe/ZrN and Fe/HfN systems were 0.343, 0.114, and 0.030 $J/m^2$, respectively. Influence of bond energy was estimated using the discrete lattice plane/nearest neighbor broken bond(DLP/NNBB) model. It was found that the dependence of interface energy on the type of nitride was closely related to changes of the bond energies between Fe, X and N atoms before and after formation of the Fe/XN interfaces. The misfit strain energies in Fe/TiN, Fe/ZrN, and Fe/HfN systems were 0.239, 1.229, and 0.955 eV per 16 atoms(Fe; 8 atoms and XN; 8 atoms). More misfit strain energy was generated as the difference of lattice parameters between the bulk Fe and the bulk XNs increased.

Study of Pd substitution in orthorhombic-NiSi/Si (010) structure: First principles calculation (Orthorhombic-NiSi/Si (010) 구조의 Pd 치환 연구: 제 1 원리 계산)

  • Kim, Dae-Hee;Kim, Dae-Hyun;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Semiconductor & Display Technology
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    • v.7 no.4
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    • pp.41-44
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    • 2008
  • NiSi is less stable than the previously-used $CoSi_2$ at high temperature. Some noble metals, such as Pd and Pt, have been added to NiSi to improve its thermal stability. We employed a first principles calculation to understand the Pd segregation at the interface. An orthorhombic structure of NiSi was used to construct an orthorhombic-NiSi/Si (010). Lattice parameters along a- and c-axes in orthorhombic-NiSi were matched with those of Si for epitaxy contact. The optimized $1\times4\times1$ orthorhombic-NiSi (010) and $1\times2\times1$ Si (010) superstructures were put together to construct the orthorhombic-NiSi/Si (010), and the superstructure was relieved in calculation to minimize its total free energy. The optimized interface thickness of the superstructure was $1.59\AA$. Pd atom was substituted in Ni and Si sites located near interface. Both Ni and Si sites located at the interface were favorable for Pd substitution.

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A First-principles Study on Magnetism of $Fe_2 /Ir_4$(001) Superlattice

  • Kim, Jae Il;Lee, In Gee
    • Journal of Magnetics
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    • v.6 no.3
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    • pp.80-82
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    • 2001
  • We have investigated magnetism of $Fe_2 /Ir_4$(001) superlattice in terms of a first-principles calculation by using an all-electron full-potential linearized augmented plane-wave (FLAPW) method within the generalized gradient approximation (GGA). We considered two magnetic states, the ferromagnetic (FM) and antiferromagnetic (AFM) coupled states between the Fe layers. It was found that the FM state was energetically more stable than the AFM one by 0.166 eV. Calculated magnetic moments of the Fe layers were, in absolute values, 2.45$\mu_B$ and 2.30 $\mu_B$for the FM and AFM states, respectively. We also found that the Ir layers had very small magnetic moments less than 0.1 $\mu_B$ for both magnetic states. In all the magnetic states, the subinterface Ir layers were coupled antiferromagnetically to the interface Ir layers, while the interface Ir layers were always coupled frerromagnetically to the interface Fe layers. These results contradicted to recent experimental reports of magnetically "dead"Fe layers in Fe/Ir superlattices for which the Fe layer thickness was less than two atomic layers. We attributed that the experimentally observed "dead"Fe layers were due to possible interdiffusion between Ir and Fe layers.en Ir and Fe layers.

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Structural Study of Tetragonal-Ni1-xMxSi/Si (001) (M = Co, Pd, Pt): First Principles Calculation (Tetragonal-Ni1-xMxSi/Si (001) (M = Co, Pd, Pt) 구조연구 : 제 1 원리계산)

  • Kim, Dae-Hee;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Korean Journal of Metals and Materials
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    • v.46 no.12
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    • pp.830-834
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    • 2008
  • NiSi is currently being employed in 45 nm CMOS devices as a contact material. We employed a first principles calculation to understand the movements of atoms when Co, Pd, and Pt were added to tetragonal-NiSi on Si (001). The Ni atoms in the tetragonal-NiSi/Si (001) favored away from the original positions along positive c-direction in a systematic way during the energy minimization. Two different Ni sites were identified at the interface and the bulk, respectively. The Ni site at the interface farther away from the interface was more favorable for Pd and Pt substitution. Co, however, prafered the bulk site to the interface site, unlike Pd and Pt.

A First Principles Study of Mn on AlGaP2 Semiconductor Surface (AlGaP2 반도체내와 표면의 Mn에 대한 제일원리 해석)

  • Kang, Byung Sub
    • Journal of the Semiconductor & Display Technology
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    • v.20 no.1
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    • pp.12-17
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    • 2021
  • The electronic and magnetic properties for Mn-adsorbed on the chalcopyrite (CH) AlGaP2 semiconductor are investigated by using first-principles FPLMTO method. The clean CH-AlGaP2 without adsorbed Mn is a p-type semiconductor with a direct band-gap. The Mn-adsorbed CH-AlGaP2 exhibits the ferromagnetic state. It is more energetically stable than the other magnetic ones. The interstitial site on P-terminated surface is more energetically favorable one than the Al/Ga-terminated surface, or the other adsorbing sites. In the case of Mn-adsorbed Al/Ga-terminated surface, it is induced a strong coupling between Mn-3d and neighboring P-3p electrons. The holes of partially unoccupied minority Mn-3d state and majority (or minority) Al-3p or P-3p state are induced. Thus a high magnetic moment of Mn is sustained by holes-mediated double-exchange coupling. It is noticeable that the semiconducting and half-metallic characteristics of CH-AlGaP2:Mn thin film is disappeared.

First-principles investigation of the monoclinic NaMnO2 cathode material for rechargeable Na-ion batteries

  • Zhang, Renhui;Lu, Zhibin;Yang, Yingchang;Shi, Wei
    • Current Applied Physics
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    • v.18 no.11
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    • pp.1431-1435
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    • 2018
  • Using first-principles calculations, we successfully investigate the electrochemical performance of the monoclinic $NaMnO_2$ for the sodium ion batteries. $NaMnO_2$ possesses a voltage window of 3.54-2.52 V and theoretical reversible capacity of $136mAh\;g^{-1}$. Besides, we find that the metallicity of the monoclinic $NaMnO_2$ gradually increases during Na extraction. Moreover, the computational Na migration energy barrier in the monoclinic $NaMnO_2$ is 0.18 eV, ensuring ideal conductivity and reversible capacity. Although the Jahn-Teller distortion effects limit the enhancement of the reversible capacity of the monoclinic $NaMnO_2$, it is still a right cathode material for the sodium ion batteries. The computational results are well in consistent with the experimental investigations.

The mechanical and thermodynamic properties of α-Na3(U0.84(2),Na0.16(2))O4: A combined first-principles calculations and quasi-harmonic Debye model study

  • Chen, Haichuan
    • Nuclear Engineering and Technology
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    • v.53 no.2
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    • pp.611-617
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    • 2021
  • The mechanical properties of α-Na3(U0.84(2),Na0.16(2))O4 have been researched using the first-principles calculations combined with the quasi-harmonic Debye model. The obtained lattice parameters agree well with the published experimental data. The results of elastic constants indicate that α-Na3(U0.84(2),Na0.16(2))O4 is mechanically stable. The polycrystalline moduli are predicted. The results show that the α-Na3(U0.84(2),Na0.16(2))O4 exhibits brittleness and possesses obvious elastic anisotropy. The hardness shows that it can be considered a "soft material". Furthermore, the Debye temperature θD and the minimum thermal conductivity kmin are also discussed, respectively. Finally, the thermal expansion coefficient α, isobaric heat capacity CP and isochoric heat capacity CV are evaluated through the quasi-harmonic Debye model.

On the Internet Securities Transaction (인터넷에 의한 증권거래에 관하여 - ILA. Committee on International Securities Regulation에서의 논의 -)

  • 박영길
    • Journal of Arbitration Studies
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    • v.12 no.2
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    • pp.221-262
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    • 2003
  • In recent years, information technological revolution of using Internet in the Stock Market has shown reconsideration of Securities and Exchange Law. Since the 1998 Taipei Conference, ILA have studied upon it and presented 6th Interim Report during the 2000 London Conference. This paper summarizes a part of the 6th Interim Report. The Internet has created a medium to which traditional principles of jurisdiction may not have full relevance. To understand the jurisdictional issues posed by this new medium, we should first review the traditional principles of jurisdiction under international, U. S. law and Other Countries law. In previous reports, the general principles of jurisdiction in international law have been described. These principles are, however, difficult to apply in the context of Internet and other forms of computerized securities trading. Regulators all over the world are trying to address and solve jurisdictional issues raised by the Internet. The traditional rules of jurisdiction in international law, grounded as they are on a geography-based approach, may be in the process of being undermined by the Internet and other global networks allowing for remote access to information and to markets.

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