Novel ultra-hard hexacarbon allotropes from first principles

Mapping Intimacies ◽

10.26434/chemrxiv-2022-x4p38 ◽

2022 ◽

Author(s):

Samir F. Matar ◽

Vladimir L. Solozhenko

Keyword(s):

Elastic Constants ◽

Vickers Hardness ◽

Ground State ◽

First Principles ◽

Geometry Optimization ◽

Band Gaps ◽

Electronic Band ◽

Carbon Allotropes ◽

Ground State Structures ◽

Electronic Band Structures

Novel ultra-hard hexacarbon C6 allotropes are proposed based on crystal chemistry rationale and geometry optimization onto ground state structures. Similar to diamond, the orthorhombic, tetragonal and trigonal C6 are cohesive networks of C4 tetrahedra illustrated by charge density projections exhibiting sp3-like carbon hybridization. All three allotropes are identified as mechanically (elastic constants) and dynamically (phonons) stable. The electronic band structures are characteristic of insulators with large band gaps of 4 to 5 eV, like diamond. From three different models evaluating Vickers hardness HV, all new carbon allotropes are identified as ultra-hard.

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Electronic Properties of Hydrogenated Graphene-Like Materials Under Strains

MRS Proceedings ◽

10.1557/opl.2014.501 ◽

2014 ◽

Vol 1658 ◽

Author(s):

K. Mihara ◽

K. Shintani

Keyword(s):

Band Gap ◽

First Principles ◽

Tensile Strain ◽

Band Gaps ◽

First Principles Calculation ◽

Honeycomb Lattice ◽

Electronic Band ◽

Hydrogenated Graphene ◽

Zigzag Direction ◽

Electronic Band Structures

ABSTRACTThe electronic band structures of the hydrogenated graphene-like materials, graphane, silicane, and germanane, under tensile strains are calculated using first-principles calculation. The imposed tensile strain is in either the armchair or zigzag direction in the honeycomb lattice. It is found that the band gap of graphane gradually increases with the increase of the strain, whereas the band gaps of silicane and germanane decrease with the increase of the strain. There is little effect of the direction of the imposed strain on such strain dependences.

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Electronic properties of monolayer molybdenum dichalcogenides under strains

MRS Proceedings ◽

10.1557/opl.2015.466 ◽

2015 ◽

Vol 1726 ◽

Author(s):

J. Sugimoto ◽

K. Shintani

Keyword(s):

First Principles ◽

Tensile Strain ◽

Compressive Strain ◽

Band Gaps ◽

First Principles Calculation ◽

Honeycomb Lattice ◽

Biaxial Strain ◽

Electronic Band ◽

Zigzag Direction ◽

Electronic Band Structures

ABSTRACTThe electronic band structures of monolayer molybdenum dichalcogenides, MoS2, MoSe2, and MoTe2 under either uniaxial or biaxial strain are calculated using first-principles calculation with the GW method. The imposed uniaxial strain is in the zigzag direction in the honeycomb lattice whereas the imposed biaxial strain is in the zigzag and armchair directions. It is found that the band gaps of these dichalcogenides almost linearly increase with the decrease of the magnitude of compressive strain, reach their maxima at some compressive strain, and then decrease almost linearly with the increase of tensile strain. It is also found their maximum band gaps are direct bandgaps.

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STABLE STRUCTURES, ELECTRIC AND MAGNETIC PROPERTIES OF NANOPARTICLES COn(n = 1-6) CLUSTERS: FIRST-PRINCIPLES CALCULATIONS

International Journal of Modern Physics B ◽

10.1142/s0217979213620075 ◽

2013 ◽

Vol 27 (15) ◽

pp. 1362007

Author(s):

JUN LIU ◽

SHENG-BIAO TAN ◽

HUI-NING DONG

Keyword(s):

Magnetic Properties ◽

Ground State ◽

First Principles ◽

Lower Energy ◽

Magnetic Moments ◽

Molecular Orbitals ◽

First Principles Calculations ◽

Half Metallicity ◽

Ground State Structures ◽

Stable Structures

The ground state geometric structures of the nanoparticles or clusters CO n(n = 1-6) were given based on the first-principles calculations. Then the magnetic properties of the clusters CO n(n = 1-6) and ( CO n)-2(n = 1-6) were calculated in system. Results show that their ground state structures are closely related to the numbers of O-ions. These clusters have no magnetic moments and half-metallicity if they are electroneutral. However, they have magnetic moments if they have positive or negative charges. The total magnetic moments of the clusters ( CO n)-2(n = 1-6, but n≠3) are all 2.0000 μB, and all their ions have contributions to the total magnetic moments. The main reason is that the molecular orbitals with lower energy filled with paired electrons and the molecular orbitals with higher energy are occupied by two electrons in parallel.

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First-principles investigation of the electronic band structures and optical properties of quaternary ABaMQ4 (A = Rb, Cs; M = P, V; and Q = S) metal chalcogenides

International Journal of Modern Physics B ◽

10.1142/s021797921850337x ◽

2018 ◽

Vol 32 (30) ◽

pp. 1850337

Author(s):

Shahid Ullah ◽

Hayat Ullah ◽

Abdullah Yar ◽

Sikander Azam ◽

A. Laref

Keyword(s):

Optical Properties ◽

First Principles ◽

Density Functional ◽

Correlation Energy ◽

Electronic Charge ◽

Electromagnetic Spectrum ◽

Metal Chalcogenides ◽

Electronic Band ◽

Charge Densities ◽

Electronic Band Structures

In this paper, we study the optoelectronic properties of quaternary metal chalcogenide semiconductor ABaMQ4 (A = Rb, Cs; M = P, V; and Q = S) compounds using state-of-the-art density functional theory (DFT) with TB-mBJ approximation for the treatment of exchange-correlation energy. In particular, the electronic and optical properties of the relaxed geometries of these compounds are investigated. Our first-principles ab-initio calculations show that the CsBaPS4 and RbBaPS4 compounds have direct bandgaps whereas the CsBaVS4 compound exhibits indirect bandgap nature. Importantly, the theoretically calculated values of the bandgaps of the compounds are consistent with experiment. Furthermore, our analysis of the electronic charge densities of these compounds indicates that the above quaternary chalcogenides have mixed covalent and ionic bonding characters. The effective masses of these compounds are also calculated which provide very useful information about the band structure and transport characteristics of the investigated compounds. Similarly, high absorptivity in the visible and ultraviolet regions of the electromagnetic spectrum possibly predicts and indicates the importance of these materials for potential optoelectronic applications in this range.

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Physical Properties Investigations of Ternary-Layered Carbides M2PbC (M = Ti, Zr and Hf): First-Principles Calculations

Crystals ◽

10.3390/cryst11121445 ◽

2021 ◽

Vol 11 (12) ◽

pp. 1445

Author(s):

Tahani A. Alrebdi ◽

Mohammed Benali Kanoun ◽

Souraya Goumri-Said

Keyword(s):

Elastic Constants ◽

First Principles ◽

Mechanical Stability ◽

Electronic Band Structure ◽

Max Phase ◽

Mechanical And Thermal Properties ◽

First Principles Calculations ◽

Electronic Band ◽

Bonding Properties ◽

Structure Density

We investigated structure optimization, mechanical stability, electronic and bonding properties of the nanolaminate compounds Ti2PbC, Zr2PbC, and Hf2PbC using the first-principles calculations. These structures display nanolaminated edifices where MC layers are interleaved with Pb. The calculation of formation energies, elastic moduli and phonons reveal that all MAX phase systems are exothermic, and are intrinsically and dynamically stable at zero and under pressure. The mechanical and thermal properties are reported with fundamental insights. Results of bulk modulus and shear modulus show that the investigated compounds display a remarkable hardness. The elastic constants C11 and C33 rise more quickly with an increase in pressure than that of other elastic constants. Electronic and bonding properties are investigated through the calculation of electronic band structure, density of states, and charge densities.

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Accurate Prediction of Band Structure of FeS2: A Hard Quest of Advanced First-Principles Approaches

Frontiers in Chemistry ◽

10.3389/fchem.2021.747972 ◽

2021 ◽

Vol 9 ◽

Author(s):

Min-Ye Zhang ◽

Hong Jiang

Keyword(s):

Band Structure ◽

First Principles ◽

High Energy ◽

Accurate Prediction ◽

Band Gaps ◽

Full Potential ◽

Band Structures ◽

Electronic Band ◽

Fundamental Band ◽

Hybrid Functionals

The pyrite and marcasite polymorphs of FeS2 have attracted considerable interests for their potential applications in optoelectronic devices because of their appropriate electronic and optical properties. Controversies regarding their fundamental band gaps remain in both experimental and theoretical materials research of FeS2. In this work, we present a systematic theoretical investigation into the electronic band structures of the two polymorphs by using many-body perturbation theory with the GW approximation implemented in the full-potential linearized augmented plane waves (FP-LAPW) framework. By comparing the quasi-particle (QP) band structures computed with the conventional LAPW basis and the one extended by high-energy local orbitals (HLOs), denoted as LAPW + HLOs, we find that one-shot or partially self-consistent GW (G0W0 and GW0, respectively) on top of the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation with a converged LAPW + HLOs basis is able to remedy the artifact reported in the previous GW calculations, and leads to overall good agreement with experiment for the fundamental band gaps of the two polymorphs. Density of states calculated from G0W0@PBE with the converged LAPW + HLOs basis agrees well with the energy distribution curves from photo-electron spectroscopy for pyrite. We have also investigated the performances of several hybrid functionals, which were previously shown to be able to predict band gaps of many insulating systems with accuracy close or comparable to GW. It is shown that the hybrid functionals considered in general fail badly to describe the band structures of FeS2 polymorphs. This work indicates that accurate prediction of electronic band structure of FeS2 poses a stringent test on state-of-the-art first-principles approaches, and the G0W0 method based on semi-local approximation performs well for this difficult system if it is practiced with well-converged numerical accuracy.

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FIRST-PRINCIPLES STUDY OF STRUCTURES AND ELECTRONIC PROPERTIES FOR NITRIDE-DOPED ALUMINUM CLUSTERS

International Journal of Modern Physics B ◽

10.1142/s0217979205031018 ◽

2005 ◽

Vol 19 (15n17) ◽

pp. 2380-2385 ◽

Cited By ~ 3

Author(s):

BAOLIN WANG ◽

DALING SHI ◽

XIAOSHUANG CHEN ◽

GUANGHOU WANG ◽

JIJUN ZHAO

Keyword(s):

Genetic Algorithm ◽

Electronic Properties ◽

Atomic Structure ◽

Ground State ◽

First Principles ◽

Cluster Size ◽

Aluminum Clusters ◽

Structural And Electronic Properties ◽

Ground State Structures ◽

Homo Lumo

By using Gaussian98 package at BPW91 6-31g(d,p) level combined a genetic algorithm (GA) simulation, we have studied the lowest energy structural and electronic properties of the Al n N ( n =2-13) clusters. The ground-state structures, the charge transfers from Al to N site, HOMO-LUMO gap and the covalent, ionic and metallic nature with cluster size and atomic structure are investigated. Al 7 N , Al 9 N and Al 12 N cluster is found particularly stable among the Al n N clusters.

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