scholarly journals Existence of yttrium allotrope with incommensurate host-guest structure at moderate pressure: First evidence from computational approach

2021 ◽  
Author(s):  
Prutthipong Tsuppayakorn-aek ◽  
Thipok Bovornratanaraks ◽  
Wei Luo ◽  
Rajeev Ahuja ◽  
Thiti Bovornratanaraks
Keyword(s):  
First Principles ◽  
Computational Approach ◽  
First Principles Calculation ◽  
Random Structure ◽  
Electron Localization ◽  
Moderate Pressure ◽  
Metallic Element ◽  
Host Structure ◽  
The Stability ◽  
Weak Electron

Abstract We predict an allotrope of yttrium with an incommensurate host-guest structure by using ab initio random structure searching technique, based on first-principles calculation. Along with, we propose a set analogous commensurate supercells, which is incommensurate ratio (c H /c G), by approximating the different the number of guest atoms in channels in along c axis of the host structure. Herein, our results show that c H /c G = 5/4 is energetically stable. Subsequently, an incommensurate host-guest structure is found to be thermodynamically and dynamically stable within harmonic level. The hybridization of spd explains the stability of the host-guest structure under high pressure conditions. The distributions of electrons between the host and guest atoms are indicated strong and weak electron localization of spd bonds. This findings suggest that the host-guest structure is more likely to be achieved experimentally in this metallic element at moderate pressure.

Stability and Reactivity of [11-20] Step in Initial Stage of Epitaxial Graphene Growth on SiC(0001)

2014 ◽  
Vol 778-780 ◽  
pp. 1150-1153
Author(s):  
Hiroyuki Kageshima ◽  
Hiroki Hibino ◽  
Hiroshi Yamaguchi ◽  
Masao Nagase
Keyword(s):  
Surface Morphology ◽  
First Principles ◽  
Epitaxial Graphene ◽  
First Principles Calculation ◽  
Control Parameters ◽  
Graphene Growth ◽  
Initial Stage ◽  
The Stability

The energetics for the Si desorption and the C adsorption at a [11-20] step on SiC(0001) surface are studied using the first-principles calculation. It is found that the [11-20] step is stable and nonreactive. The stability of the step is thought to govern the surface morphology during the graphene formation. It is shown that the Si pressure and the temperature are the control parameters for the surface morphology and the graphene quality.

scholarly journals Effects of Doped Elements (Si, Cr, W and Nb) on the Stability, Mechanical Properties and Electronic Structures of MoAlB Phase by the First-Principles Calculation

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4221
Author(s):  
Yongxin Jian ◽  
Zhifu Huang ◽  
Yu Wang ◽  
Jiandong Xing
Keyword(s):  
Mechanical Properties ◽  
Chemical Bonding ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Formation Enthalpy ◽  
First Principles Calculation ◽  
Elemental Doping ◽  
The Stability ◽  
W Doping

First-principles calculations based on density functional theory (DFT) have been performed to explore the effects of Si, Cr, W, and Nb elements on the stability, mechanical properties, and electronic structures of MoAlB ternary boride. The five crystals, with the formulas of Mo4Al4B4, Mo4Al3SiB4, Mo3CrAl4B4, Mo3WAl4B4, and Mo3NbAl4B4, have been respectively established. All the calculated crystals are thermodynamically stable, according to the negative cohesive energy and formation enthalpy. By the calculation of elastic constants, the mechanical moduli and ductility evolutions of MoAlB with elemental doping can be further estimated, with the aid of B/G and Poisson’s ratios. Si and W doping cannot only enhance the Young’s modulus of MoAlB, but also improve the ductility to some degree. Simultaneously, the elastic moduli of MoAlB are supposed to become more isotropic after Si and W addition. However, Cr and Nb doping plays a negative role in ameliorating the mechanical properties. Through the analysis of electronic structures and chemical bonding, the evolutions of chemical bondings can be disclosed with the addition of dopant. The enhancement of B-B, Al/Si-B, and Al/Si-Mo bondings takes place after Si substitution, and W addition apparently intensifies the bonding with B and Al. In this case, the strengthening of chemical bonding after Si and W doping exactly accounts for the improvement of mechanical properties of MoAlB. Additionally, Si doping can also improve the Debye temperature and melting point of the MoAlB crystal. Overall, Si element is predicted to be the optimized dopant to ameliorate the mechanical properties of MoAlB.

First-principles study of Cu adsorption on vacancy-defected/Au-doped graphene

2018 ◽  
Vol 32 (11) ◽  
pp. 1850139 ◽  
Author(s):  
Yang Liu ◽  
Libao An ◽  
Liang Gong
Keyword(s):  
First Principles ◽  
Population Analysis ◽  
First Principles Calculation ◽  
Matrix Composites ◽  
Mulliken Population ◽  
Vacancy Defects ◽  
Subsequent Investigation ◽  
Doped Graphene ◽  
The Stability ◽  
P Type

To enhance the interaction between Cu and graphene in graphene reinforced Cu matrix composites, the first principles calculation was carried out to study the adsorption of Cu atoms on graphene. P-type doping and n-type doping were formed, respectively, on vacancy-defected and Au-doped graphene based on band structure analysis, and this was verified by subsequent investigation on density of states. A computation on charge transfer confirmed that p-type doping could promote the electron transport between Cu and graphene, while n-type doping would prevent it. In addition, adsorption energy and Mulliken population analysis revealed that both vacancy defects and Au doping could improve the stability of the Cu–graphene system. The research conducted in this paper provides useful guidance for the preparation of Cu/graphene composites.

The stability of 3C-SiC(111) on Si(111) Thin Films: First-principles calculation

2021 ◽  
pp. 138318
Author(s):  
Eric K.K. Abavare ◽  
Bright Kwakye-Awuah ◽  
Oswald A. Nunoo ◽  
Peter Amoako-Yirenkyire ◽  
G. Gebreyesus ◽  
...  
Keyword(s):  
Thin Films ◽  
First Principles ◽  
First Principles Calculation ◽  
The Stability

scholarly journals Critical Thermodynamic Conditions for the Formation of p-Type β-Ga2O3 with Cu Doping

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5161
Author(s):  
Chuanyu Zhang ◽  
Zhibing Li ◽  
Weiliang Wang
Keyword(s):  
Oxygen Partial Pressure ◽  
First Principles ◽  
Electronic Structures ◽  
First Principles Calculation ◽  
Third Generation ◽  
Cu Doping ◽  
Thermodynamic Conditions ◽  
The Stability ◽  
P Type ◽  
Formation Energies

As a promising third-generation semiconductor, β-Ga2O3 is facing bottleneck for its p-type doping. We investigated the electronic structures and the stability of various Cu doped structures of β-Ga2O3. We found that Cu atoms substituting Ga atoms result in p-type conductivity. We derived the temperature and absolute oxygen partial pressure dependent formation energies of various doped structures based on first principles calculation with dipole correction. Then, the critical thermodynamic condition for forming the abovementioned substitutional structure was obtained.

scholarly journals Effects of Defects and Doping on an Al Atom Adsorbed on Graphene: A First-Principles Investigation

Coatings ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 131
Author(s):  
Xiaoshuang Dai ◽  
Tao Shen ◽  
Jiaojiao Chen ◽  
Hongchen Liu
Keyword(s):  
Optical Absorption ◽  
First Principles ◽  
Theoretical Basis ◽  
Optoelectronic Devices ◽  
Red Shift ◽  
First Principles Calculation ◽  
Future Application ◽  
Pristine Graphene ◽  
Doped Graphene ◽  
The Stability

In order to enhance the interaction between an Al atom and graphene in graphene-reinforced aluminum-based composites, the method of first-principles calculation was used to investigate the adsorption behavior of Al atoms on graphene. Our calculations indicate that defective and doped graphene are energetically favored for Al atom adsorption compared with pristine graphene. The adsorption effects show that both defects and doping can improve the stability of the Al–graphene system. Furthermore, it was also found that defects and doping lead to a red-shift of the highest optical absorption peaks. The results of the investigation provide a theoretical basis for the future application of graphene-reinforced aluminum-based composites in optical and optoelectronic devices.

scholarly journals First-Principles Calculation on Initial Stage of Oxidation of Si (110)-(1 × 1) Surface

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Takahiro Nagasawa ◽  
Koji Sueoka
Keyword(s):  
First Principles ◽  
Experimental Results ◽  
The Other ◽  
First Principles Calculation ◽  
Preferential Oxidation ◽  
Coverage Ratio ◽  
Surface Areas ◽  
Initial Stage ◽  
The Stability

The initial stage of oxidation of an Si (110)-(1 × 1) surface was analyzed by using the first-principles calculation. Two calculation cells with different surface areas were prepared. In these cells, O atoms were located at the Si–Si bonds in the first layer (A-bonds) and at the Si–Si bonds between the first and second layers (B-bonds). We found that (i) the most stable site of one O atom was the A-bond, and (ii) an O (A-bond) –Si–O (A-bond) was the most stable for two O atoms with a coverage ratio of while an O (A-bond) –Si–O (B-bond) was the most stable for . The stability of O (A-bond) –Si–Si–O (A-bond) was less than the structures obtained in (ii). The other calculations showed that the unoxidized A-bonds should be left when a coverage ratio of is close to 1. These simulations suggest that the O atoms will form clusters in the initial stage of oxidation, and the preferential oxidation will change from the A-bonds to the B-bonds up to the formation of 1 monolayer (ML) oxide. The results obtained here support the reported experimental results.

scholarly journals Influence of Nickel Addition on the Stability, Trapping, and Diffusion Behaviour of Hydrogen in Vanadium: A First-Principles Investigation

2021 ◽  
Author(s):  
Jiayao Qin ◽  
Zhigao Liu ◽  
Wei Zhao ◽  
Dianhui Wang ◽  
Yanli Zhang ◽  
...  
Keyword(s):  
First Principles ◽  
Effective Means ◽  
Interstitial Site ◽  
First Principles Calculation ◽  
Hydrogen Energy ◽  
Ni Doping ◽  
Octahedral Interstitial Site ◽  
The Stability ◽  
And Diffusion ◽  
Diffusion Behaviour

Abstract Hydrogen embrittlement causes deterioration of materials used in hydrogen energy systems. Alloying is an effective means for overcoming this issue. In this study, the first-principles calculation method was used to investigate the effects of alloying Ni on the stability, dissolution, trapping, and diffusion behaviour of interstitial/vacancy H atoms in V. The calculated phonon spectra and solution energies of the vacancy/interstitial H atoms revealed that the V–Ni phase was dynamically and thermodynamically stable, and Ni addition could reduce the stability of V hydrides and improve their resistance to H embrittlement. H atoms in the interstitials and vacancies preferentially occupied the tetrahedral interstitial site (TIS) and octahedral interstitial site (OIS) with the lowest solution energies and diffused along the TIS → TIS and OIS → OIS paths with the minimum diffusion barrier energies. The trapping energy of the vacancy H atoms indicated that the addition of Ni could reduce the H trapping capability of the vacancies and suppress the retention of H in V. Detailed analysis of the calculated H diffusion barriers indicated that the presence of monovacancy defects blocked the diffusion of H atoms more than the presence of interstitials, and Ni doping did not enhance the H diffusion coefficient.

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