Shobhna Dhiman - Academia.edu (original) (raw)
Papers by Shobhna Dhiman
Materials Today: Proceedings, Jun 1, 2023
Materials today communications, Aug 1, 2023
Advanced theory and simulations, May 12, 2023
arXiv (Cornell University), Jun 4, 2020
Magnetic carbon nano-structures have potential applications in the field of spintronics as they e... more Magnetic carbon nano-structures have potential applications in the field of spintronics as they exhibit valuable magnetic properties. Symmetrically sized small fullerene dimers are substitutional doped with nitrogen (electron rich) and boron (electron deficient) atoms to visualize the effect on their magnetic properties. Interaction energies suggests that the resultant dimer structures are energetically favourable and hence can be formed experimentally. There is significant change in the total magnetic moment of dimers of the order of 0.5 µ B after the substitution of C atoms with N and B, which can also be seen in the change of density of states. The HOMO-LUMO gaps of spin up and spin down electronic states have finite energy difference which confirm their magnetic behaviour, whereas for non-magnetic doped dimers, the HOMO-LUMO gaps for 1 arXiv:2006.02728v1 [physics.chem-ph] 4 Jun 2020 spin up and down states are degenerate. The optical properties show that the dimers behave as optical semiconductors and are useful in optoelectronic devices. The induced magnetism in these dimers makes them fascinating nanocarbon magnetic materials.
International Journal of Energy Research, May 20, 2021
We explore the structural, electronic, mechanical, and thermoelectric properties of a new half He... more We explore the structural, electronic, mechanical, and thermoelectric properties of a new half Heusler compound HfPtPb, an all metallic heavy element, recently proposed to be stable [Gautier et al., Nat. Chem. 7, 308 (2015)]. In this work, we employ density functional theory and semiclassical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties, such as shear modulus, Young's modulus, elastic constants, Poisson's ratio, and shear anisotropy factor, have been investigated. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. Pugh's ratio and Frantsevich's ratio demonstrate its ductile behavior, and the shear anisotropic factor reveals the anisotropic nature of HfPtPb. The band structure predicts this compound to be a semiconductor with a band gap of 0.86 eV. The thermoelectric transport parameters, such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, have been calculated as a function of temperature. The highest value of Seebeck coefficient is obtained for n-type doping at an optimal carrier concentration of 1.0 Â 10 20 e/cm 3. We predict the maximum value of figure of merit (0.25) at 1000 K. Our investigation suggests that this material is an n-type semiconductor. Published by AIP Publishing.
SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013, 2014
Low-lying equilibrium geometric structures of Al n N (n ϭ 1-12) clusters obtained by an all-elect... more Low-lying equilibrium geometric structures of Al n N (n ϭ 1-12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spinpolarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static dipole polarizabilities are calculated for the ground-state structures within the GGA. It is observed that symmetric structures with the nitrogen atom occupying the internal position are lowest-energy geometries. Generalized gradient approximation extends bond lengths as compared with the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within the GGA. The stability analysis based on the energies clearly shows the Al 7 N cluster to be endowed with special stability.
![Research paper thumbnail of Ab initio study of structural and electronic properties of Cu[sub n]@C[sub 60]](https://attachments.academia-assets.com/112382009/thumbnails/1.jpg)
](PROCEEDING OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN APPLIED PHYSICS AND MATERIAL SCIENCE: RAM 2013, 2013
We study the atomic structure and the electronic and optical properties of Ge 2 Sb 2 Te 5 in two ... more We study the atomic structure and the electronic and optical properties of Ge 2 Sb 2 Te 5 in two different crystalline states of cubic and hexagonal structures with the use of ab initio pseudopotential density functional method. It is found that electronic and atomic structures are very sensitive to the layer sequence in the two phases. The proximity of vacancy layer to Ge layer leads to the splitting of Ge-Te bond length, which, in turn, affects the electronic and optical properties. The effect of Te d orbitals is also investigated with respect to structural properties.
Materials Today: Proceedings
Materials Today: Proceedings, 2016
The paper studies the structural, thermo-and electronic properties of the silanone group (SG, oxy... more The paper studies the structural, thermo-and electronic properties of the silanone group (SG, oxygen doublebond) as bulk defect of amorphous SiO 2 (a-SiO 2), whose supercell consists of 108 atoms, and the molecular dynamics and first principle calculations are used. The results theoretically prove the existence and good thermostability of SG as bulk defect in a-SiO 2. Besides, the electronic density of states (DOS) and orbital-resolved partial DOS (PDOS) are studied as well. The results show that new electronic state distribution in the band gap of a-SiO 2 is found, as well as reduced width of the band gap, which are produced by the SG defect.
Physical Chemistry Chemical Physics
Structural transition of AuX alloys from bulk to 2D monolayers. Thermoelectric performance of des... more Structural transition of AuX alloys from bulk to 2D monolayers. Thermoelectric performance of designed monolayers against strain and temperature.
Physica B: Condensed Matter
Journal of Materials Science: Materials in Electronics
Advances in Materials and Processing Technologies
Molecules
We hereby discuss the thermoelectric properties of PdXSn(X = Zr, Hf) half Heuslers in relation to... more We hereby discuss the thermoelectric properties of PdXSn(X = Zr, Hf) half Heuslers in relation to lattice thermal conductivity probed under effective mass (hole/electrons) calculations and deformation potential theory. In addition, we report the structural, electronic, mechanical, and lattice dynamics of these materials as well. Both alloys are indirect band gap semiconductors with a gap of 0.91 eV and 0.82 eV for PdZrSn and PdHfSn, respectively. Both half Heusler materials are mechanically and dynamically stable. The effective mass of electrons/holes is (0.13/1.23) for Zr-type and (0.12/1.12) for Hf-kind alloys, which is inversely proportional to the relaxation time and directly decides the electrical/thermal conductivity of these materials. At 300K, the magnitude of lattice thermal conductivity observed for PdZrSn is 15.16 W/mK and 9.53 W/mK for PdHfSn. The highest observed ZT value for PdZrSn and PdHfSn is 0.32 and 0.4, respectively.
Indian Journal of Physics, 2017
We have analyzed the effect of Ge and Sn doping on the electronic and thermoelectric properties o... more We have analyzed the effect of Ge and Sn doping on the electronic and thermoelectric properties of Mg 2 Si using density functional theory and Boltzmann equations. The calculated results show that Mg 2 Si 1-x A x (A = Ge, Sn, 0.125 B x B 0.5) systems exhibit semiconductor nature and doping with Ge slightly widen the energy gap at x = 0.125. In all doped systems, the seebeck coefficient has a negative sign, which indicates that conduction is due to electrons. With an increase in doping concentrations, the seebeck coefficient decreases, while electrical conductivity, electronic thermal conductivity increases. A classical kinetic theory has been employed to calculate the contribution of lattice thermal conductivity. We have elucidated that both doped systems attained minimum lattice thermal conductivity. Mg 2 Si 1-x Ge x and Mg 2 Si 1-x Sn x has maximum figure of merit 0.077 and 0.15 at x = 0.125 respectively.
Half heusler compounds have gained attention due to their excellent properties and good thermal s... more Half heusler compounds have gained attention due to their excellent properties and good thermal stability. In this paper, using first principle calculation and Boltzmann transport equation, we have investigated structural, electronic, mechanical and thermoelectric properties of PdXSn (X=Zr,Hf) half Heusler materials. These materials are indirect band gap semiconductors with band gap of 0.52 (0.44) for PdZrSn (PdHfSn). Calculations of elastic and phonon characteristics show that both materials are mechanically and dynamically stable. At 300K the magnitude of lattice thermal conductivity observed for PdZrSn is 15.16 W/mK and 9.53 W/mK for PdHfSn. The highest ZT value for PdZrSn and PdHfSn is 0.32 and 0.4 respectively.
Thermoelectricity and Advanced Thermoelectric Materials, 2021
Journal of Materials Science: Materials in Electronics, 2021
In this paper, room temperature multiferroic behaviour in Ni (Nickel)-doped NBT (Na0.5Bi0.5TiO3) ... more In this paper, room temperature multiferroic behaviour in Ni (Nickel)-doped NBT (Na0.5Bi0.5TiO3) ceramics synthesized using solid state reaction technique have been investigated. Structural, dielectric, ferroelectric, magnetic and magneto-dielectric properties were consistently probed with the increment in transition metal doping. XRD peaks were indexed for the monoclinic Cc phase. SEM micrographs clearly depicted the reduction of grain size with addition of Ni content. Ferroelectric polarization (P) vs applied electric field (E) hysteresis curves shows an increase in lossy behaviour with an increase in Ni content. The room temperature magnetization (M) vs applied magnetic field (H) curves depict the weak ferromagnetic ordering on increasing the Ni doping. Enhanced magneto-dielectric change of 1.26% was observed in 25% Ni-doped NBT ceramic, which may be useful in the development of novel non-volatile lead-free multiferroic memory devices.
Computational Materials Science, 2021
Abstract Half-Heuslers (HH) have found ever-increasing popularity as high temperature thermoelect... more Abstract Half-Heuslers (HH) have found ever-increasing popularity as high temperature thermoelectric (TE) materials. In this paper, the electron and phonon transport equations are solved to understand the thermoelectric character of the PtXSn (X = Zr, Hf) compounds. Here, we have elucidated the phonon stability, electronic properties, thermoelectric response from lattice thermal conductivity, and phonon dependent parameters. The PtXSn compounds reveal an indirect bandgap semiconducting nature with a gap of 1.23 eV and 0.94 eV for PtZrSn and PtHfSn, respectively. At room temperature, a low magnitude of lattice thermal conductivity (κl) for PtZrSn (16.96 W/mK) and PtHfSn (10.04 W/mK) compounds is observed. The calculated maximum value of ZT is 0.57 and 0.24 observed for PtHfSn and 0.24 PtZrSn, respectively. Our present investigation demonstrate that the PtHfSn compound is potentially a favorable candidate for high-temperature power generation.
Materials Today: Proceedings, Jun 1, 2023
Materials today communications, Aug 1, 2023
Advanced theory and simulations, May 12, 2023
arXiv (Cornell University), Jun 4, 2020
Magnetic carbon nano-structures have potential applications in the field of spintronics as they e... more Magnetic carbon nano-structures have potential applications in the field of spintronics as they exhibit valuable magnetic properties. Symmetrically sized small fullerene dimers are substitutional doped with nitrogen (electron rich) and boron (electron deficient) atoms to visualize the effect on their magnetic properties. Interaction energies suggests that the resultant dimer structures are energetically favourable and hence can be formed experimentally. There is significant change in the total magnetic moment of dimers of the order of 0.5 µ B after the substitution of C atoms with N and B, which can also be seen in the change of density of states. The HOMO-LUMO gaps of spin up and spin down electronic states have finite energy difference which confirm their magnetic behaviour, whereas for non-magnetic doped dimers, the HOMO-LUMO gaps for 1 arXiv:2006.02728v1 [physics.chem-ph] 4 Jun 2020 spin up and down states are degenerate. The optical properties show that the dimers behave as optical semiconductors and are useful in optoelectronic devices. The induced magnetism in these dimers makes them fascinating nanocarbon magnetic materials.
International Journal of Energy Research, May 20, 2021
We explore the structural, electronic, mechanical, and thermoelectric properties of a new half He... more We explore the structural, electronic, mechanical, and thermoelectric properties of a new half Heusler compound HfPtPb, an all metallic heavy element, recently proposed to be stable [Gautier et al., Nat. Chem. 7, 308 (2015)]. In this work, we employ density functional theory and semiclassical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties, such as shear modulus, Young's modulus, elastic constants, Poisson's ratio, and shear anisotropy factor, have been investigated. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. Pugh's ratio and Frantsevich's ratio demonstrate its ductile behavior, and the shear anisotropic factor reveals the anisotropic nature of HfPtPb. The band structure predicts this compound to be a semiconductor with a band gap of 0.86 eV. The thermoelectric transport parameters, such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, have been calculated as a function of temperature. The highest value of Seebeck coefficient is obtained for n-type doping at an optimal carrier concentration of 1.0 Â 10 20 e/cm 3. We predict the maximum value of figure of merit (0.25) at 1000 K. Our investigation suggests that this material is an n-type semiconductor. Published by AIP Publishing.
SOLID STATE PHYSICS: Proceedings of the 58th DAE Solid State Physics Symposium 2013, 2014
Low-lying equilibrium geometric structures of Al n N (n ϭ 1-12) clusters obtained by an all-elect... more Low-lying equilibrium geometric structures of Al n N (n ϭ 1-12) clusters obtained by an all-electron linear combination of atomic orbital approach, within spinpolarized density functional theory, are reported. The binding energy, dissociation energy, and stability of these clusters are studied within the local spin density approximation (LSDA) and the three-parameter hybrid generalized gradient approximation (GGA) due to Becke-Lee-Yang-Parr (B3LYP). Ionization potentials, electron affinities, hardness, and static dipole polarizabilities are calculated for the ground-state structures within the GGA. It is observed that symmetric structures with the nitrogen atom occupying the internal position are lowest-energy geometries. Generalized gradient approximation extends bond lengths as compared with the LSDA lengths. The odd-even oscillations in the dissociation energy, the second differences in energy, the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gaps, the ionization potential, the electron affinity, and the hardness are more pronounced within the GGA. The stability analysis based on the energies clearly shows the Al 7 N cluster to be endowed with special stability.
PROCEEDING OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN APPLIED PHYSICS AND MATERIAL SCIENCE: RAM 2013, 2013
We study the atomic structure and the electronic and optical properties of Ge 2 Sb 2 Te 5 in two ... more We study the atomic structure and the electronic and optical properties of Ge 2 Sb 2 Te 5 in two different crystalline states of cubic and hexagonal structures with the use of ab initio pseudopotential density functional method. It is found that electronic and atomic structures are very sensitive to the layer sequence in the two phases. The proximity of vacancy layer to Ge layer leads to the splitting of Ge-Te bond length, which, in turn, affects the electronic and optical properties. The effect of Te d orbitals is also investigated with respect to structural properties.
Materials Today: Proceedings
Materials Today: Proceedings, 2016
The paper studies the structural, thermo-and electronic properties of the silanone group (SG, oxy... more The paper studies the structural, thermo-and electronic properties of the silanone group (SG, oxygen doublebond) as bulk defect of amorphous SiO 2 (a-SiO 2), whose supercell consists of 108 atoms, and the molecular dynamics and first principle calculations are used. The results theoretically prove the existence and good thermostability of SG as bulk defect in a-SiO 2. Besides, the electronic density of states (DOS) and orbital-resolved partial DOS (PDOS) are studied as well. The results show that new electronic state distribution in the band gap of a-SiO 2 is found, as well as reduced width of the band gap, which are produced by the SG defect.
Physical Chemistry Chemical Physics
Structural transition of AuX alloys from bulk to 2D monolayers. Thermoelectric performance of des... more Structural transition of AuX alloys from bulk to 2D monolayers. Thermoelectric performance of designed monolayers against strain and temperature.
Physica B: Condensed Matter
Journal of Materials Science: Materials in Electronics
Advances in Materials and Processing Technologies
Molecules
We hereby discuss the thermoelectric properties of PdXSn(X = Zr, Hf) half Heuslers in relation to... more We hereby discuss the thermoelectric properties of PdXSn(X = Zr, Hf) half Heuslers in relation to lattice thermal conductivity probed under effective mass (hole/electrons) calculations and deformation potential theory. In addition, we report the structural, electronic, mechanical, and lattice dynamics of these materials as well. Both alloys are indirect band gap semiconductors with a gap of 0.91 eV and 0.82 eV for PdZrSn and PdHfSn, respectively. Both half Heusler materials are mechanically and dynamically stable. The effective mass of electrons/holes is (0.13/1.23) for Zr-type and (0.12/1.12) for Hf-kind alloys, which is inversely proportional to the relaxation time and directly decides the electrical/thermal conductivity of these materials. At 300K, the magnitude of lattice thermal conductivity observed for PdZrSn is 15.16 W/mK and 9.53 W/mK for PdHfSn. The highest observed ZT value for PdZrSn and PdHfSn is 0.32 and 0.4, respectively.
Indian Journal of Physics, 2017
We have analyzed the effect of Ge and Sn doping on the electronic and thermoelectric properties o... more We have analyzed the effect of Ge and Sn doping on the electronic and thermoelectric properties of Mg 2 Si using density functional theory and Boltzmann equations. The calculated results show that Mg 2 Si 1-x A x (A = Ge, Sn, 0.125 B x B 0.5) systems exhibit semiconductor nature and doping with Ge slightly widen the energy gap at x = 0.125. In all doped systems, the seebeck coefficient has a negative sign, which indicates that conduction is due to electrons. With an increase in doping concentrations, the seebeck coefficient decreases, while electrical conductivity, electronic thermal conductivity increases. A classical kinetic theory has been employed to calculate the contribution of lattice thermal conductivity. We have elucidated that both doped systems attained minimum lattice thermal conductivity. Mg 2 Si 1-x Ge x and Mg 2 Si 1-x Sn x has maximum figure of merit 0.077 and 0.15 at x = 0.125 respectively.
Half heusler compounds have gained attention due to their excellent properties and good thermal s... more Half heusler compounds have gained attention due to their excellent properties and good thermal stability. In this paper, using first principle calculation and Boltzmann transport equation, we have investigated structural, electronic, mechanical and thermoelectric properties of PdXSn (X=Zr,Hf) half Heusler materials. These materials are indirect band gap semiconductors with band gap of 0.52 (0.44) for PdZrSn (PdHfSn). Calculations of elastic and phonon characteristics show that both materials are mechanically and dynamically stable. At 300K the magnitude of lattice thermal conductivity observed for PdZrSn is 15.16 W/mK and 9.53 W/mK for PdHfSn. The highest ZT value for PdZrSn and PdHfSn is 0.32 and 0.4 respectively.
Thermoelectricity and Advanced Thermoelectric Materials, 2021
Journal of Materials Science: Materials in Electronics, 2021
In this paper, room temperature multiferroic behaviour in Ni (Nickel)-doped NBT (Na0.5Bi0.5TiO3) ... more In this paper, room temperature multiferroic behaviour in Ni (Nickel)-doped NBT (Na0.5Bi0.5TiO3) ceramics synthesized using solid state reaction technique have been investigated. Structural, dielectric, ferroelectric, magnetic and magneto-dielectric properties were consistently probed with the increment in transition metal doping. XRD peaks were indexed for the monoclinic Cc phase. SEM micrographs clearly depicted the reduction of grain size with addition of Ni content. Ferroelectric polarization (P) vs applied electric field (E) hysteresis curves shows an increase in lossy behaviour with an increase in Ni content. The room temperature magnetization (M) vs applied magnetic field (H) curves depict the weak ferromagnetic ordering on increasing the Ni doping. Enhanced magneto-dielectric change of 1.26% was observed in 25% Ni-doped NBT ceramic, which may be useful in the development of novel non-volatile lead-free multiferroic memory devices.
Computational Materials Science, 2021
Abstract Half-Heuslers (HH) have found ever-increasing popularity as high temperature thermoelect... more Abstract Half-Heuslers (HH) have found ever-increasing popularity as high temperature thermoelectric (TE) materials. In this paper, the electron and phonon transport equations are solved to understand the thermoelectric character of the PtXSn (X = Zr, Hf) compounds. Here, we have elucidated the phonon stability, electronic properties, thermoelectric response from lattice thermal conductivity, and phonon dependent parameters. The PtXSn compounds reveal an indirect bandgap semiconducting nature with a gap of 1.23 eV and 0.94 eV for PtZrSn and PtHfSn, respectively. At room temperature, a low magnitude of lattice thermal conductivity (κl) for PtZrSn (16.96 W/mK) and PtHfSn (10.04 W/mK) compounds is observed. The calculated maximum value of ZT is 0.57 and 0.24 observed for PtHfSn and 0.24 PtZrSn, respectively. Our present investigation demonstrate that the PtHfSn compound is potentially a favorable candidate for high-temperature power generation.