Ayub Faridi | University of the Punjab (original) (raw)

Papers by Ayub Faridi

Chinese Journal of Physics, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  Study reports under pressure electronic band gap transition in KNbO 3  Compound become brittle (covalent) to ductile (ionic) at 150 GPa.  Thermal conductivity increases, while anisotropy decreases with pressure.

Chinese Journal of Physics, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  Study provides plausible temperature range for electron-phonon couplings.  Elastic and thermal properties are the first study of compound.  By using PBE-GGA, STO exhibits anti-ferromagnetic structure.  mBJ-GGA study shows ferromagnetic attributes.  Ferromagnetic frustration arises due to Sr-p and O-s electronic states.

Journal of Physics and Chemistry of Solids, 2018

The pressure-induced indirect to direct bandgap transition and thermoelectric response in SrTiO 3... more The pressure-induced indirect to direct bandgap transition and thermoelectric response in SrTiO 3 : An abinitio study,

Journal of Superconductivity and Novel Magnetism, 2017

A systematic study of the magnetism, mechanical, and optical behaviors of Mg 0.75 TM 0.25 S/Se (T... more A systematic study of the magnetism, mechanical, and optical behaviors of Mg 0.75 TM 0.25 S/Se (TM = Fe, Co, Ni) ordered alloys was conducted using the fullpotential linearized augmented plane wave plus local orbital method. The ferromagnetic (FM) and antiferromagnetic (AFM) ground state energy differences and enthalpy of formation scrutinized their dynamical stability in the FM state. The elastic parameters decided their mechanical stability, ductile behavior, and partial ionic and covalent characters. Moreover, the calculated band structures and density of states revealed the type and origin of magnetism in terms of exchange splitting energies and exchange constants. The Fe-and Ni-doped MgS/Se alloys exhibited half metallic ferromagnetic (HMF) characteristics, while the Co-doped MgS/Se alloy depicted ferromagnetic semiconducting characters. A reduction in the magnetic moments of Q. Mahmood

Current Applied Physics, 2015

Abstract We have theoretically investigated the structural, elastic, electronic and magnetic prop... more Abstract We have theoretically investigated the structural, elastic, electronic and magnetic properties of Be 0.75 Co 0.25 Y (Y S, Se and Te) alloys, in their zinc-blend phase. This study is carried out by using the full-potential augmented plane wave plus local orbitals method within the density functional theory. Foe computing the exchange-correlation potential, the Wu and Cohen generalized gradient approximation is employed to calculate structural and elastic properties whereas the modified Becke and Johnson potential local density approximation is utilized to examine electronic and magnetic properties. By minimizing the total energy in paramagnetic (PM) and ferromagnetic (FM) phases, it is found the studied compounds are stable in FM structure. The mechanical behavior of the studied compounds is reported with the calculation of shear modulus, Young's modulus, and Poisson's ratio provides. Such mechanical aspects might be useful for the experimentalists to study the mechanical properties upon alloying BeY compounds with Co. We also compute electronic structures, density of states (total and partial), pd -exchange splitting and magnetic moments. Moreover, bond nature is studied by estimating the spin polarized charge densities of Be 0.75 Co 0.25 Y (Y S, Se and Te).

High Temperatures-High Pressures, 2020

In the enclosure of density functional theory along with GGA (generalized gradient approximation)... more In the enclosure of density functional theory along with GGA (generalized gradient approximation), incorporated in Wien2k code has been utilized to explore structural, electronic and mechanical properties of SrNbO3 (SNO). It has been found that spin-polarized phase of SNO is most stable at 60 GPa with the calculated lattice constant of 3.801 Å. The calculated lattice constant and bulk modulus at 0 GPa are found to be in agreement with literature. The present calculations predict that SNO is stable and antiferromagnetic in nature up to 60 GPa. The calculated charge density contours and Cauchy pressure depicts majority of the bonding nature between the content atoms of SNO is ionic with a small contribution of covalent bond. The band-gap is found traverse from indirect R-Г gap under 0 GPa to wider direct Г-Г gap under 60 GPa. Furthermore, calculated elastic constants, C11, C12 and C44 suggest that compound is stable up to 60 GPa and exhibits ductile, anisotropic nature. Beneficial ele...

arXiv (Cornell University), Jun 17, 2017

By using semi-analytical method,we investigate the transmission and reflection coefficient and ab... more By using semi-analytical method,we investigate the transmission and reflection coefficient and absorption and scattering cross section of spin 0,1,2 particles which are massless from a charged nonrotating black holes. Here orbiting scattering can be characterized of massless particles from Reissner-Nordstrom black hole at a critical angular momentum. We examine the effects upon reflection,transmission,scattering and absorption cross section due to the black hole charge. We find that with the increase of charge the absorption cross section decreased in spin-2 particle while in case of spin 0 particle it is reversed and in case of spin 1 the effect is negligible due to charge.

In this sutdy, a static synchronous series compensator (SSSC) is used to investigate the effect o... more In this sutdy, a static synchronous series compensator (SSSC) is used to investigate the effect of this device in controlling active and reactive powers as well as damping power system oscillations in transient mode. The SSSC equipped with a source of energy in the DC link can supply or absorb the reactive and active power to or from the line.

AIP Conference Proceedings, 2007

The Role of Free Falling Hypersurfaces. [AIP Conference Proceedings 888, 274 (2007)]. Ayub Faridi... more The Role of Free Falling Hypersurfaces. [AIP Conference Proceedings 888, 274 (2007)]. Ayub Faridi, Amjad Pervez, Haris Rashid, Fazal‐e‐Aleem. Abstract. In General Relativity, free falling hypersurfaces play an important role. ...

Vacuum, 2011

We present the update on the emission characteristics and results from previously reported (Vacuu... more We present the update on the emission characteristics and results from previously reported (Vacuum 77 (2004) 19e26), experimental study of axial point source thermionic electron beam emitter assembly. Emission characteristics for this gun have been presented. Optimal conditions to obtain the requisite beam characteristics for welding of refractory metals at 10 keV energy are reported.

Chinese Physics Letters, 2006

Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete ... more Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everywhere except at the singularity r = 0 the mean extrinsic curvature becomes infinity.

International Cosmic …, 2003

Relativistic Heavy Ion Collider and Large Hadron Colliders have special agenda for the measuremen... more Relativistic Heavy Ion Collider and Large Hadron Colliders have special agenda for the measurements of the total cross sections at high energies giving us an opportunity to touch cosmic ray energies. Recent analyses of the cosmic ray data together with earlier experimental measurements at ISR and SPS gives us an insight about the behaviour of this important parameter at asymptotic energies. We will study the growth of total cross section at high energies in the light of various theoretical approaches with special reference to measurements at RHIC and LHC.

Computational Materials Science, 2007

arXiv: High Energy Physics - Phenomenology, 2005

Recent analysis of the cosmic ray data together with earlier experimental measurements at ISR and... more Recent analysis of the cosmic ray data together with earlier experimental measurements at ISR and SPS provides us a sound footing to discuss the behavior of total cross section at asymptotic energies. We will study the growth of total cross section at high energies in the light of various theoretical approaches with special reference to measurements at RHIC and LHC.

arXiv: Materials Science, 2015

Structural properties of Mild Steel have been modified by embedding Carbon Nanotubes in its matri... more Structural properties of Mild Steel have been modified by embedding Carbon Nanotubes in its matrix. The embedment was done by forming a composite at the surface of MS with the help of a thermionic electron beam source at an acceleration potential of 5 kV and beam current of 45 mA. Structural analysis was carried out by X-Ray Diffraction(XRD). Stress and strain were reduced about three times while the crystalline size was reduced to 22% after embedment of Carbon Nanotubes. Surface morphology was observed by Scanning Electron Microscope (SEM) and composition was examined by Energy Dispersive X-Ray Spectroscopy(EDX) respectively. Average grain size of the modified sample was reduced from 1.94 micrometre to 720 nm whereas the hardness was increased to 30% for as received samples.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

Abstract The present work reports the in-situ ion beam induced luminescence measurements using 2 ... more Abstract The present work reports the in-situ ion beam induced luminescence measurements using 2 MeV proton excitation of LiF single crystal with the aim of obtaining a further insight on F-type centers kinetics and its correlation with the self-trapped exciton (STE). It is found that the STE luminescence intensity decreases from the beginning of irradiation. While the dose-dependent evolution of F3+ and F2 centers reveals three kinetic stages: (i) linear increase from the beginning of irradiation up to 10.1 MGy, followed by (ii) monotonic decrease to 18.1 MGy, and (iii) steady state from 18.1 to 26.2 MGy where the luminescence intensity remains constant. The STE luminescence completely extinguished at high dose; 18.1 MGy in our case. Whereas, the F3+ and F2 luminescence persist and remain constant above 18.1 MGy. The latter behavior revealed in the present study can be useful for LiF application in radiation dosimetry and an imaging detector.

Chinese Journal of Physics, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  Study reports under pressure electronic band gap transition in KNbO 3  Compound become brittle (covalent) to ductile (ionic) at 150 GPa.  Thermal conductivity increases, while anisotropy decreases with pressure.

Chinese Journal of Physics, 2018

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Highlights  Study provides plausible temperature range for electron-phonon couplings.  Elastic and thermal properties are the first study of compound.  By using PBE-GGA, STO exhibits anti-ferromagnetic structure.  mBJ-GGA study shows ferromagnetic attributes.  Ferromagnetic frustration arises due to Sr-p and O-s electronic states.

Journal of Physics and Chemistry of Solids, 2018

The pressure-induced indirect to direct bandgap transition and thermoelectric response in SrTiO 3... more The pressure-induced indirect to direct bandgap transition and thermoelectric response in SrTiO 3 : An abinitio study,

Journal of Superconductivity and Novel Magnetism, 2017

A systematic study of the magnetism, mechanical, and optical behaviors of Mg 0.75 TM 0.25 S/Se (T... more A systematic study of the magnetism, mechanical, and optical behaviors of Mg 0.75 TM 0.25 S/Se (TM = Fe, Co, Ni) ordered alloys was conducted using the fullpotential linearized augmented plane wave plus local orbital method. The ferromagnetic (FM) and antiferromagnetic (AFM) ground state energy differences and enthalpy of formation scrutinized their dynamical stability in the FM state. The elastic parameters decided their mechanical stability, ductile behavior, and partial ionic and covalent characters. Moreover, the calculated band structures and density of states revealed the type and origin of magnetism in terms of exchange splitting energies and exchange constants. The Fe-and Ni-doped MgS/Se alloys exhibited half metallic ferromagnetic (HMF) characteristics, while the Co-doped MgS/Se alloy depicted ferromagnetic semiconducting characters. A reduction in the magnetic moments of Q. Mahmood

Current Applied Physics, 2015

Abstract We have theoretically investigated the structural, elastic, electronic and magnetic prop... more Abstract We have theoretically investigated the structural, elastic, electronic and magnetic properties of Be 0.75 Co 0.25 Y (Y S, Se and Te) alloys, in their zinc-blend phase. This study is carried out by using the full-potential augmented plane wave plus local orbitals method within the density functional theory. Foe computing the exchange-correlation potential, the Wu and Cohen generalized gradient approximation is employed to calculate structural and elastic properties whereas the modified Becke and Johnson potential local density approximation is utilized to examine electronic and magnetic properties. By minimizing the total energy in paramagnetic (PM) and ferromagnetic (FM) phases, it is found the studied compounds are stable in FM structure. The mechanical behavior of the studied compounds is reported with the calculation of shear modulus, Young's modulus, and Poisson's ratio provides. Such mechanical aspects might be useful for the experimentalists to study the mechanical properties upon alloying BeY compounds with Co. We also compute electronic structures, density of states (total and partial), pd -exchange splitting and magnetic moments. Moreover, bond nature is studied by estimating the spin polarized charge densities of Be 0.75 Co 0.25 Y (Y S, Se and Te).

High Temperatures-High Pressures, 2020

In the enclosure of density functional theory along with GGA (generalized gradient approximation)... more In the enclosure of density functional theory along with GGA (generalized gradient approximation), incorporated in Wien2k code has been utilized to explore structural, electronic and mechanical properties of SrNbO3 (SNO). It has been found that spin-polarized phase of SNO is most stable at 60 GPa with the calculated lattice constant of 3.801 Å. The calculated lattice constant and bulk modulus at 0 GPa are found to be in agreement with literature. The present calculations predict that SNO is stable and antiferromagnetic in nature up to 60 GPa. The calculated charge density contours and Cauchy pressure depicts majority of the bonding nature between the content atoms of SNO is ionic with a small contribution of covalent bond. The band-gap is found traverse from indirect R-Г gap under 0 GPa to wider direct Г-Г gap under 60 GPa. Furthermore, calculated elastic constants, C11, C12 and C44 suggest that compound is stable up to 60 GPa and exhibits ductile, anisotropic nature. Beneficial ele...

arXiv (Cornell University), Jun 17, 2017

By using semi-analytical method,we investigate the transmission and reflection coefficient and ab... more By using semi-analytical method,we investigate the transmission and reflection coefficient and absorption and scattering cross section of spin 0,1,2 particles which are massless from a charged nonrotating black holes. Here orbiting scattering can be characterized of massless particles from Reissner-Nordstrom black hole at a critical angular momentum. We examine the effects upon reflection,transmission,scattering and absorption cross section due to the black hole charge. We find that with the increase of charge the absorption cross section decreased in spin-2 particle while in case of spin 0 particle it is reversed and in case of spin 1 the effect is negligible due to charge.

In this sutdy, a static synchronous series compensator (SSSC) is used to investigate the effect o... more In this sutdy, a static synchronous series compensator (SSSC) is used to investigate the effect of this device in controlling active and reactive powers as well as damping power system oscillations in transient mode. The SSSC equipped with a source of energy in the DC link can supply or absorb the reactive and active power to or from the line.

AIP Conference Proceedings, 2007

The Role of Free Falling Hypersurfaces. [AIP Conference Proceedings 888, 274 (2007)]. Ayub Faridi... more The Role of Free Falling Hypersurfaces. [AIP Conference Proceedings 888, 274 (2007)]. Ayub Faridi, Amjad Pervez, Haris Rashid, Fazal‐e‐Aleem. Abstract. In General Relativity, free falling hypersurfaces play an important role. ...

Vacuum, 2011

We present the update on the emission characteristics and results from previously reported (Vacuu... more We present the update on the emission characteristics and results from previously reported (Vacuum 77 (2004) 19e26), experimental study of axial point source thermionic electron beam emitter assembly. Emission characteristics for this gun have been presented. Optimal conditions to obtain the requisite beam characteristics for welding of refractory metals at 10 keV energy are reported.

Chinese Physics Letters, 2006

Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete ... more Free falling hypersurfaces in the Schwarzschild geometry have been studied to provide a complete foliation of spacetime. The hypersurfaces do not cross into the maximally extended spacetime and are well behaved everywhere except at the singularity r = 0 the mean extrinsic curvature becomes infinity.

International Cosmic …, 2003

Relativistic Heavy Ion Collider and Large Hadron Colliders have special agenda for the measuremen... more Relativistic Heavy Ion Collider and Large Hadron Colliders have special agenda for the measurements of the total cross sections at high energies giving us an opportunity to touch cosmic ray energies. Recent analyses of the cosmic ray data together with earlier experimental measurements at ISR and SPS gives us an insight about the behaviour of this important parameter at asymptotic energies. We will study the growth of total cross section at high energies in the light of various theoretical approaches with special reference to measurements at RHIC and LHC.

Computational Materials Science, 2007

arXiv: High Energy Physics - Phenomenology, 2005

Recent analysis of the cosmic ray data together with earlier experimental measurements at ISR and... more Recent analysis of the cosmic ray data together with earlier experimental measurements at ISR and SPS provides us a sound footing to discuss the behavior of total cross section at asymptotic energies. We will study the growth of total cross section at high energies in the light of various theoretical approaches with special reference to measurements at RHIC and LHC.

arXiv: Materials Science, 2015

Structural properties of Mild Steel have been modified by embedding Carbon Nanotubes in its matri... more Structural properties of Mild Steel have been modified by embedding Carbon Nanotubes in its matrix. The embedment was done by forming a composite at the surface of MS with the help of a thermionic electron beam source at an acceleration potential of 5 kV and beam current of 45 mA. Structural analysis was carried out by X-Ray Diffraction(XRD). Stress and strain were reduced about three times while the crystalline size was reduced to 22% after embedment of Carbon Nanotubes. Surface morphology was observed by Scanning Electron Microscope (SEM) and composition was examined by Energy Dispersive X-Ray Spectroscopy(EDX) respectively. Average grain size of the modified sample was reduced from 1.94 micrometre to 720 nm whereas the hardness was increased to 30% for as received samples.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

Abstract The present work reports the in-situ ion beam induced luminescence measurements using 2 ... more Abstract The present work reports the in-situ ion beam induced luminescence measurements using 2 MeV proton excitation of LiF single crystal with the aim of obtaining a further insight on F-type centers kinetics and its correlation with the self-trapped exciton (STE). It is found that the STE luminescence intensity decreases from the beginning of irradiation. While the dose-dependent evolution of F3+ and F2 centers reveals three kinetic stages: (i) linear increase from the beginning of irradiation up to 10.1 MGy, followed by (ii) monotonic decrease to 18.1 MGy, and (iii) steady state from 18.1 to 26.2 MGy where the luminescence intensity remains constant. The STE luminescence completely extinguished at high dose; 18.1 MGy in our case. Whereas, the F3+ and F2 luminescence persist and remain constant above 18.1 MGy. The latter behavior revealed in the present study can be useful for LiF application in radiation dosimetry and an imaging detector.