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Pressure and atomic size effects of IV cation on mechanical and electronic properties of Zn-IV-N2 (IV[dbnd]Si, Ge and Sn): First principles calculation
(2024-09-01)
Boonkhuang, Apiwat
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Kongnok, Thanundon
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Meethan, Weerachon
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Busayaporn, Wutthikrai
;
Phacheerak, Kanoknan
Zn-IV-N<inf>2</inf> compounds, incorporating Si, Ge, and Sn, have emerged as pivotal materials for their mechanical and electronic properties, influencing optoelectronic devices and photovoltaic applications. Employing density functional theory (DFT), we comprehensively investigate the structural, elastic, mechanical, and electronic characteristics of ZnIVN<inf>2</inf> (IV[dbnd]Si, Ge, Sn) under ambient and pressure conditions up to 20 GPa. Our findings suggest that a larger atomic size of the group IV cation can be more easily compressed than a smaller size. The mechanical stability criteria and the phonon dispersion show mechanical and dynamic stability in both ambient pressure and under high pressure up to 20 GPa. The ZnSiN<inf>2</inf> and ZnGeN<inf>2</inf> exhibit linear increments in bulk modulus (B), shear modulus (G), and Young's modulus (E) under pressure, while ZnSnN<inf>2</inf> experiences a decrease in G and E. Notably, the energy gap of ZnSiN<inf>2</inf>, ZnGeN<inf>2</inf>, and ZnSnN<inf>2</inf> (4.62 eV indirect, 2.82 eV, 1.16 eV, respectively) increases with pressure due to higher N s orbital energy, approaching the UV region. In the valence band, a hybridization of N p and Si/Ge/Sn p orbitals is observed, offering opportunities to tailor the band gap for optimal applications in optoelectronic devices. Preferentially adjusting group-IV elements over group-II elements is recommended for optimizing band gap modulation. The correlation between larger atomic size and decreased band gap energy highlights the potential to fine-tune material properties through controlled variations in group-IV elements.
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Investigating the phase transition and properties of CaSiN2 under pressure based on first-principles calculations
(2023-12-01)
Meethan, Weerachon
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Kongnok, Thanundon
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Fongkaew, Ittipon
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Bootchanont, Atipong
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Saisopa, Thanit
In this study, we apply first-principles calculations to examine the pressure-induced phase transformation of CaSiN<inf>2</inf> in a range of pressure of 0–100 GPa. Its pressure-induced transitions at 1.3 GPa, 15.3 GPa, and 55.8 GPa followed the order of α- CaSiN<inf>2</inf> → β- CaSiN<inf>2</inf> → α- CaSiN<inf>2</inf> → γ- CaSiN<inf>2</inf>, for α- CaSiN<inf>2</inf> → β- CaSiN<inf>2</inf>, β- CaSiN<inf>2</inf> → α- CaSiN<inf>2</inf>, and α- CaSiN<inf>2</inf> → γ- CaSiN<inf>2</inf>, respectively. The stability of the phases of CaSiN<inf>2</inf> was confirmed based on calculations of the Born criterion of elastic stability. Its behavior transitioned in the sequence of brittle (0–1.3 GPa) → ductile (1.3–55.8 GPa) → brittle (55.8–100 GPa). The structure of its projected orbital band reflected insulating behavior by CaSiN<inf>2</inf> under a range of pressure of 0–55.8 GPa with a direct band gap, which transformed into metallic behavior by the γ- CaSiN<inf>2</inf> phase under pressures higher than 55.8 GPa, due to a shift in energy to higher levels around the Γ point of the N p orbitals and Si p orbitals. The Si-N bonds in CaSiN<inf>2</inf> were found to be covalent, while ionic bonding dominated the Ca-Si and Ca-N bonds in the range of pressure of 0–100 GPa. We also investigate and discuss its mechanical properties, Vickers hardness (H<inf>v</inf>), average sound velocity v<inf>m,</inf> and Debye temperature (θ<inf>D</inf>).
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Influence of pressure on elasticity, mechanical properties, and Li diffusion in battery electrode material LiCoO2: First-principles calculations
(2023-09-01)
Sailuam, Wutthigrai
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Fongkaew, Ittipon
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Busayaporn, Wutthikrai
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Klinkla, Rakchat
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Phacheerak, Kanoknan
This study used first-principles calculations based on density functional theory with generalized gradient approximation (GGA) of the Perdew Burke and Ernzerhof (PBE) parameterized form to investigate the influence of pressure on the structural, elastic, and mechanical properties of rhombohedral LiCoO<inf>2</inf>. The results indicate that rhombohedral LiCoO<inf>2</inf> remains stable up to 10 GPa. The calculated ground state properties agree well with experimental and other calculation data, validating the approach. Additionally, the calculated elastic constants, bulk modulus, Young's modulus, shear modulus, and Poisson's ratio at 0 GPa agree with previous results. The study found that all elastic constants continuously increase with increasing pressure. The deformation resistances along the axial direction are stronger than those in shape. The relationship between elasticity and length is such that C<inf>11</inf> > C<inf>33</inf>, indicating that the incompressibility along the a axis is stronger than that along the c axis. The analysis of Poisson's ratio (ν) and Pugh's criterion B/G strongly suggests that rhombohedral LiCoO<inf>2</inf> exhibits ductile behavior under pressure up to 10 GPa. The material is clearly anisotropic behavior, but the material exhibits improved isotropic behavior as pressure increases. Regarding Li ion diffusion in rhombohedral LiCoO<inf>2</inf>, the study found that the migration pathway for Li ions in rhombohedral LiCoO<inf>2</inf> is a direct route that extends from the V<inf>Li</inf> site to the closest Li site. The diffusion process is hindered by a diffusion energy barrier of 0.87 eV, which is in good agreement with available theoretical data. Furthermore, the Li ion diffusion energy barrier increases with pressure because the decrease in d<inf>mean</inf> and polyhedral volume, along with changes in angle and torsional distortion factors of CoO<inf>6</inf> octahedra, which can reduce the charging and discharging speeds of Li-ion batteries that use rhombohedral LiCoO<inf>2</inf> as the cathode material.
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A first principles investigation on the structural, elastic, and mechanical properties of MAX phase M3AlC2 (M= Ta, Ti, V) as a function of pressure
(2022-03-01)
Sailuam, Wutthigrai
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Fongkaew, Ittipon
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Limpijumnong, Sukit
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Phacheerak, Kanoknan
This study investigated the structural, elastic, and mechanical properties of hexagonal M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) within MAX phases by first-principles calculations. The considered properties of M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) compounds at 0 GPa were in reasonable agreement with available experimental and other theoretical data. The elastic stability shows that no structural phase transition occurred in pressure up to 20 GPa for all compounds. The resistances to linear compression were more forceful than the resistances to compression in shape. The bulk modulus, shear modulus, and Young's modulus for M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) compounds follow the order Ta<inf>3</inf>AlC<inf>2</inf> > V<inf>3</inf>AlC<inf>2</inf> > Ti<inf>3</inf>AlC<inf>2</inf>. The Bader charge analysis result shows the increasing of covalence bond in their structure after the pressure increased. Furthermore, Pugh's criterion B/G and Poisson's ratio v confirmed that the M<inf>3</inf>AlC<inf>2</inf> (M = Ta, Ti, and V) compounds had intrinsic brittleness. The sound velocity and Debye temperature of all compounds increased with pressure increasing. The bond stiffness and the shear anisotropy affected by pressure were reported and discussed.
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Elastic and mechanical properties of hydroxyapatite under pressure: A first-principles investigation
(2020-09-01)
Sailuam, Wutthigrai
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Phacheerak, Kanoknan
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Atipong bootchanont
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Fongkaew, Ittipon
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Limpijumnong, Sukit
The structural, elastic, and mechanical properties of hydroxyapatite (HAp) were investigated by generalized gradient approximation (GGA) in the functional form by Perdew, Bruke, and Ernzerhof (PBE) exchange-correlation functional using density-functional theory. Our calculated equilibrium lattice parameters at ambient pressure are in good agreement with the experimental and previous theoretical results. The details of the structural, mechanical, and electrical properties such as elastic constants, bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratioν, Cauchy pressure, shear anisotropic factor A, and total density of states under pressure ranging 0 GPa to 10 GPa are studied. The lattice parameters a and c are found to be decreased with increasing pressure. Moreover, the lattice parameter a is more sensitive to external pressure than c. The calculated elastic constants of hexagonal HAp increase with increasing pressure. The elastic constants C<inf>11</inf> and C<inf>33,</inf> which represent the elasticity in length are larger than the elasticity in shape, which represent by the elastic constants C<inf>12</inf>, C<inf>13</inf>, C<inf>44</inf>, and C<inf>66</inf>. The deformation resistances along the axial direction are stronger than the deformation resistances in shape. The calculated B/G, Poisson's ratio ν, and Cauchy pressure show that the hexagonal HAp behaves as a ductility material at ambient pressure and has more ductile under pressure. While the calculated shear anisotropic factor A indicate that the HAp shows elastic anisotropy under pressure. Moreover, calculated total density of states (DOS) show that HAp becomes more insulator property with increasing pressure.

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