scholarly journals Ab Initio Study of the Electronic, Vibrational, and Mechanical Properties of the Magnesium Diboride Monolayer

2019 ◽  
Vol 4 (2) ◽  
pp. 37 ◽  
Author(s):  
Jelena Pešić ◽  
Igor Popov ◽  
Andrijana Šolajić ◽  
Vladimir Damljanović ◽  
Kurt Hingerl ◽  
...  
Keyword(s):  
Ab Initio ◽  
First Principles ◽  
Materials Science ◽  
Magnesium Diboride ◽  
Poisson Ratio ◽  
Single Layer ◽  
First Principles Calculations ◽  
Significant Interest ◽  
Science Community ◽  
Fundamental Research

Magnesium diboride gained significant interest in the materials science community after the discovery of its superconductivity, with an unusually high critical temperature of 39 K. Many aspects of the electronic properties and superconductivity of bulk MgB 2 and thin sheets of MgB 2 have been determined; however, a single layer of MgB 2 has not yet been fully theoretically investigated. Here, we present a detailed study of the structural, electronic, vibrational, and elastic properties of monolayer MgB 2 , based on ab initio methods. First-principles calculations reveal the importance of reduction of dimensionality on the properties of MgB 2 and thoroughly describe the properties of this novel 2D material. The presence of a negative Poisson ratio, higher density of states at the Fermi level, and a good dynamic stability under strain make the MgB 2 monolayer a prominent material, both for fundamental research and application studies.

scholarly journals First Principles Calculations of Defects in Unstable Crystals: Austenitic Iron

2011 ◽  
Vol 1363 ◽  
Author(s):  
G.J. Ackland ◽  
T.P.C. Klaver ◽  
D.J. Hepburn
Keyword(s):  
Point Defects ◽  
First Principles ◽  
Defect Formation ◽  
Single Layer ◽  
Temperature Limit ◽  
Reference State ◽  
First Principles Calculations ◽  
General Picture ◽  
Bcc Iron ◽  
Defect Energies

ABSTRACTFirst principles calculations have given a new insight into the energies of point defects in many different materials, information which cannot be readily obtained from experiment. Most such calculations are done at zero Kelvin, with the assumption that finite temperature effects on defect energies and barriers are small. In some materials, however, the stable crystal structure of interest is mechanically unstable at 0K. In such cases, alternate approaches are needed. Here we present results of first principles calculations of austenitic iron using the VASP code. We determine an appropriate reference state for collinear magnetism to be the antiferromagnetic (001) double-layer (AFM-d) which is both stable and lower in energy than other possible models for the low temperature limit of paramagnetic fcc iron. Another plausible reference state is the antiferromagnetic (001) single layer (AFM-1). We then consider the energetics of dissolving typical alloying impurities (Ni, Cr) in the materials, and their interaction with point defects typical of the irradiated environment. We show that the calculated defect formation energies have fairly high dependence on the reference state chosen: in some cases this is due to instability of the reference state, a problem which does not seem to apply to AFM-d and AFM-1. Furthermore, there is a correlation between local free volume magnetism and energetics. Despite this, a general picture emerge that point defects in austenitic iron have geometries similar to those in simpler, non-magnetic, thermodynamically stable FCC metals. The defect energies are similar to those in BCC iron. The effect of substitutional Ni and Cr on defect properties is weak, rarely more than tenths of eV, so it is unlikely that small amounts of Ni and Cr will have a significant effect on the radiation damage in austenitic iron at high temperatures.

Semiconducting two-dimensional group VA–VA haeckelite compounds with superior carrier mobility

2020 ◽  
Vol 22 (21) ◽  
pp. 12260-12266
Author(s):  
Xin-Yue Lin ◽  
Fan-Shun Meng ◽  
Qi-Chao Liu ◽  
Qi Xue ◽  
Hui Zhang
Keyword(s):  
First Principles ◽  
Carrier Mobility ◽  
Single Layer ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Dimensional Group ◽  
Binary Group

A series of two-dimensional (2D) single-layer binary group VA–VA crystals, where VA represents P, As, Sb and Bi, are explored by the first-principles calculations.

First Principles Calculations for Metal/Ceramic Interfaces

1994 ◽  
Vol 357 ◽  
Author(s):  
M. W. Finnis ◽  
C. Kruse ◽  
U. SchÖnberger
Keyword(s):  
Electronic Structure ◽  
High Resolution ◽  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Work Of Adhesion ◽  
First Principles Calculations ◽  
Resolution Electron ◽  
Metal Ceramic

AbstractWe discuss the recent first principles calculations of the properties of interfaces between metals and oxides. This type of calculation is parameter-free, and exploits the density functional theory in the local density approximation to obtain the electronic structure of the system. At the same time the equilibrium atomic structure is sought, which minimises the excess energy of the interface. Up to now calculations of this type have been made for a few model interfaces which are atomically coherent, that is with commensurate lattices. Examples are Ag/MgO and Nb/Al2O3. In these cases it has been possible to predict the structures observed by high resolution electron microscopy. The calculations are actually made in a supercell geometry, in which there are alternating nanolayers of metal and ceramic. Because of the effectiveness of metallic screening in particular, the interfaces between the nanolayers do not interfere much with each other.Besides the electronic structure of the interface, such calculations have provided values of the ideal work of adhesion. Electrostatic image forces in conjunction with the elementary ionic model provide a simple framework for understanding the results.An important role of such calculations is to develop intuition about the nature of the bonding, including the effects of charge transfer, which has formerly only been described in an empirical way. It may then be possible to build atomistic models of the metal/ceramic interaction which have a sound physical basis and can be calibrated against ab initio results. Simpler models are necessary if larger systems, including misfit dislocations and other defects, are to be simulated, with a view to understanding the atomic processes of growth and failure. Another area in which ab initio calculations can be expected to contribute is in the chemistry of impurity segregation and its effect at interfaces. Such theoretical tools are a natural partner to the experimental technique of high resolution electron energy loss spectroscopy for studying the local chemical environment at an interface.

scholarly journals Stable anisotropic single-layer of ReTe2: a first principles prediction

2020 ◽  
Vol 44 (5) ◽  
pp. 450-457
Author(s):  
Mehmet YAĞMURCUKARDEŞ
Keyword(s):  
Raman Spectrum ◽  
Band Gap ◽  
First Principles ◽  
Anisotropic Material ◽  
Poisson Ratio ◽  
Single Layer ◽  
Mechanical Parameters ◽  
Lattice Orientation ◽  
Layer Form ◽  
Distorted Phase

In order to investigate the structural, vibrational, electronic, and mechanical features of single-layer ReTe2first-principles calculations are performed. Dynamical stability analyses reveal that single-layer ReTe2crystallize in adistorted phase while its 1H and 1T phases are dynamically unstable. Raman spectrum calculations show that single-layer distorted phase of ReTe2exhibits 18 Raman peaks similar to those of ReS2and ReSe2. Electronically, single-layerReTe2is shown to be an indirect gap semiconductor with a suitable band gap for optoelectronic applications. In addition,it is found that the formation of Re-units in the crystal induces anisotropic mechanical parameters. The in-plane stiffnessand Poisson ratio are shown to be significantly dependent on the lattice orientation. Our findings indicate that single-layer form of ReTe2can only crystallize in a dynamically stable distorted phase formed by the Re-units. Single-layer ofdistorted ReTe2can be a potential in-plane anisotropic material for various nanotechnology applications.

First-Principles Study on the Electronic Structure of Bulk and Single-Layer Boehmite

NANO ◽  
2018 ◽  
Vol 13 (12) ◽  
pp. 1850138
Author(s):  
Seungwook Son ◽  
Dongwook Kim ◽  
Sutassana Na-Phattalung ◽  
Jisoon Ihm
Keyword(s):  
Hydrogen Bonding ◽  
First Principles ◽  
Single Layer ◽  
Layered Materials ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Promising Candidate ◽  
Electronic Band ◽  
2D Layered Materials ◽  
Electronic Band Structures

Two-dimensional (2D) or layered materials have a great potential for applications in energy storage, catalysis, optoelectronics and gas separation. Fabricating novel 2D or quasi-2D layered materials composed of relatively abundant and inexpensive atomic species is an important issue for practical usage in industry. Here, we suggest the layer-structured AlOOH (Boehmite) as a promising candidate for such applications. Boehmite is a well-known layer-structured material and a single-layer can be exfoliated from the bulk boehmite by breaking the interlayer hydrogen bonding. We study atomic and electronic band structures of both bulk and single-layer boehmite, and also obtain the single-layer exfoliation energy using first-principles calculations.

Modulating the phase transition between metallic and semiconducting single-layer MoS2 and WS2 through size effects

2015 ◽  
Vol 17 (2) ◽  
pp. 1099-1105 ◽  
Author(s):  
Ziyu Hu ◽  
Shengli Zhang ◽  
Yan-Ning Zhang ◽  
Da Wang ◽  
Haibo Zeng ◽  
...  
Keyword(s):  
Phase Transition ◽  
Electronic Properties ◽  
First Principles ◽  
Size Effects ◽  
Single Layer ◽  
First Principles Calculations ◽  
Atomic Mechanism ◽  
Junction Structure

The first-principles calculations are performed to investigate the electronic properties and atomic mechanism of the single layer MoS2 or WS2 homo-junction structure.

Widely tunable band gaps of graphdiyne: an ab initio study

2014 ◽  
Vol 16 (19) ◽  
pp. 8935-8939 ◽  
Author(s):  
Jahyun Koo ◽  
Minwoo Park ◽  
Seunghyun Hwang ◽  
Bing Huang ◽  
Byungryul Jang ◽  
...  
Keyword(s):  
Ab Initio ◽  
First Principles ◽  
Atomic Layer ◽  
Band Gaps ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Ab Initio Study ◽  
Carbon Networks ◽  
Hybrid Carbon

Functionalization of graphdiyne, a two-dimensional atomic layer of sp–sp2 hybrid carbon networks, was investigated through first-principles calculations.

Two-dimensional single-layer PC6 as promising anode materials for Li-ion batteries: The first-principles calculations study

2020 ◽  
Vol 510 ◽  
pp. 145493 ◽  
Author(s):  
Jianning Zhang ◽  
Lianqiang Xu ◽  
Chen Yang ◽  
Xiuying Zhang ◽  
Ling Ma ◽  
...  
Keyword(s):  
First Principles ◽  
Anode Materials ◽  
Single Layer ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Li Ion Batteries ◽  
Li Ion
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