After finding of the superconducting properties in iron (Fe) containing materials (LaFeAsO doped with Fluorine) , a rich number of superconductors based on these iron called pnictides and chalcogenides had been observed to superconduct at different transition temperature , , , , , , , , , . This discovery stimulates intense research to explore new superconducting materials of this kind and to reveal the physics behind these superconducting properties. The highest critical temperature TC in this family is already reached to 55K in Sm[O1-xFx]FeAs  and 56K in Gd1−xThxFeAsO . These pnictides are mainly classified into four subgroups . The first one is the 1111-type such as RFePnO where R is the rare earth element and Pn denotes the pnictide elements such as phosphorus (P) or Arsenic (As), second one is the AeFe2Pn2 abbreviated as 122-type and here Ae denotes the alkaline earth metal, AFePn is the third one denoted by 111-type, where A is the alkaline metal and the last one is the FePn or the 11-type ironbased superconductors. There are also observed some iron based materials having a thick blocking layer known as 32522 or the 42622-type iron based superconductors (FeSCs) reported in . All of these iron based superconductors are found to have a identical layered type configuration created from a Fe2+ square planar layer that are tetrahedrally coordinated with anions of pnictogen i.e., P or As , , . Similar to the pnictogen, the chalcogenids are attached to chalcogen (Ch); Ch=S, Se or Te , , . It is found that this Fe2+ layers are mainly responsible for the superconducting properties in FeSCs, similar to that of the CuO2 layer in cuprates . In normal state, these iron based families show some metallic behaviour and most of the undoped materials or the parent compounds of FeSC undergo a spin density wave (SDW) magnetic transition which disappear upon electrons or holes doping in the ionic layer (FeAs) or by applying pressure , . At low temperature, a phase transition is also observed from tetragonal to orthorhombic crystal structure. While among all of the four series most of the 111 family found to be an exception; not showing any phase transition and the absence of SDW order , . This family also show relatively low transition temperature TC in comparison with other FeSCs. It was also found that to describe the physical mechanism and the observed high transition temperature of this FeSCs, the coupling provided by the electron–phonon is too weak , . So to achieve a theoretical understanding of superconductors, many theories have been proposed , , , , , , , , , but the one which bring a good explanation of all the properties is still far from the scientific community. It was also observed that the superconductivity appears close to antiferromagnetic phase , ,  both in cuprates and iron based superconductors, so we believed that the spin fluctuations i.e. based on magnetism are most promising, which was also supported by many theoretical and experimental works , , , . Because of the metallic parent state, this iron based family can be well described by the first principle density functional theory and before studying the superconducting properties, it is very much important to study the parent state of the compound, whose description is lacking in numbers. So here we study the general features of parent compound of NaFeAs system. For NaFeAs, LiFeAs, KFeAs and LiFeP i.e. the 111-type iron based superconductors, some work have already reported , , , , , which includes their electrical and superconducting properties.
In this paper, we investigated and reported the structural and electronic behaviour of NaFeAs compound. The NaFeAs compound exhibit superconducting properties at ambient pressure and without doping at a critical temperature of TC=12–25K , . The Na1-xFeAs compound found to exhibit the SDW magnetic state  and due to the evaporation loss of the sodium (Na), the synthesis of NaFeAs is quite difficult . So here we use the first principle calculation to study the structural and electronic properties of NaFeAs compound. Several theoretical examinations of the properties of NaFeAs compound using the first principle density functional calculation have been reported , , , , . For better understanding of the superconducting behaviour of a compound, it is highly essential to study their fundamental properties of the undoped or parent material of that compound. So here with the help of density functional studies, we look into the different properties of NaFeAs material. In particular here the main objective of this work is to study the structural and electronic properties including their electronic band structure diagram, the total density of states (DOS) and projected/partial density of states (PDOS) of NaFeAs system. Here the convergences of the plane wave cutoff and Brilliouin zone sampling for NaFeAs have been done and by using the optimized cell parameters, the self-consistent field (SCF), band structure and density of state (DOS) calculations have been performed. The total energy, Fermi energy of the material is observed and the band structure which provides the energy range of an electron and the band gap is also calculated along high symmetric direction in the Brillion Zone. Similarly the DOS which give the information regarding the number of different states that can be occupied by electrons in a particular energy range and projected density of state (PDOS) that provide the information about the contributions of different orbitals are also mentioned. In Section 2, we briefly described the methodology or the computational approach of our studies. Section 3 represents the results and discussions part including the crystal structure in 3.1 subsection, band structure in 3.2 and density of state (DOS) in 3.3 respectively. Finally the conclusion is presented in Section 4.
In Quantum ESPRESSO , , , the structural and electronic computations were executed by employing Density Functional Theory (DFT). This Quantum ESPRESSO (QE) is a computer codes used for examining the electronic structure calculations and materials modelling. Here the electron–ion interactions of a many body system were represented by the plane wave basis sets and the atomic cores may be described by projector-Augmented wave (PAW), Ultra-Soft (US) pseudopotentials (pp) and the
At ambient condition, the tetragonal (T) structure is possessed by NaFeAs compound having the space group of P4/nmm. Here the visualisation package VESTA ,  is used for plotting and to visualize the structure of this compound. So that we can understand the different structural properties like lattice constant, atomic positions of each atom, the Fe-As distance, the volume of the unit cell, the As-Fe-As angle and how they changed after the optimization process and how this parameters
Based on above first principle calculation, we have summarized the physical properties of NaFeAs 111-type iron based superconductors.
Here we investigate the electronic and structural behaviour of 111-type NaFeAs material using Quantum ESPRESSO codes. We did the self-consistent field, band structure and DOS along with PDOS calculation by applying the optimized lattice constant obtained from vc-relax calculation. Here the structural properties of this NaFeAs compound have been explained and
CRediT authorship contribution statement
Smrutirekha Hota: Data curation, Formal analysis, Investigation, Methodology, Resources, Software, Writing – original draft. Dr. K. L. Mohanta: Conceptualization, Formal analysis, Methodology, Resources, Software, Supervision, Validation, Writing – review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
We would like to acknowledge the research facility offered by the Institute of Physics (IOP), Bhubaneswar, India.
Design and analysis of all optical latch circuit using RSOA
Materials Today: Proceedings, Volume 66, Part 7, 2022, pp. 3328-3333
Reflective SOA (RSOA) is an optical switch. Using this switch, we have designed and analyzed an all-optical latch circuit. We used cross gain modulation (XGM) and simulated verification by Matlab. All-optical Latch circuit consists of two RSOA based switches. It has two inputs and two outputs. The simulated output of the latch circuit shows the possibility of various types of applications in optical processing. The operating speed of the all-optical latch circuit is 200 Gbps. We found the values of ER, CR and Q are 54.17dB, 56.66dB and 57.76dB of latch circuit.
Mott-Insulator to Peierls Insulator Transition in the Two-Dimensional Holstein-Hubbard Model
Materials Today: Proceedings, Volume 66, Part 7, 2022, pp. 3370-3372
We propose a variational study of the two dimensional square lattice to study the phase transition from an antiferromagnetic SDW Mott insulator to the bipolaronic CDW Peierls insulator for the half-filled Holstein Hubbard model. The correlated system is dealt analytically in two different regimes according to the renormalized Coulomb correlation strength. Different unitary transformations are performed to obtain an effective electronic Hamiltonian which is solved by using the mean-field Hartree-Fock approximation for the weakly correlated electrons. For the strong interaction case, the Zuberev’s Green function technique is used to solve the effective model at the mean field limit. The variations of the effective Hubbard hopping parameter and the effective Coulomb interaction strength for different electron–electron and electron–phonon interaction coefficients have been studied. We have found a transition from the Mott-insulator to a Peierls insulator analytically for the two dimensional Holstein Hubbard model.
Effect of Fe doping on the structural, dielectric, and magnetic properties of Li V(1-X) Fe x O3 (x=0,0.1,0.3) ceramics
Materials Today: Proceedings, Volume 66, Part 7, 2022, pp. 3355-3359
The present work is on the structural, dielectric and magnetic properties of LiV(1-x)Fex O3 (x=0,0.1,0.3) ceramics samples. The Rietveld refinement of XRD pattern reveal that the crystal structure of all samples are monoclinic with space group C2/c. Structural studies also suggests that Li site disorder increases with increase in Fe doping concentration, leads to the formation of minor phase of Li3VO4. The Raman spectra shows red shift with increase in Fe content to parent LiVO3. The dielectric constant at low-frequency increase with Fe doping content and undulates at high frequency range due to grain boundary effect. The magnetic properties of LiVO3 has been significantly changed with Fe doping. The diamagnetic behavior of parent material changes to weak ferromagnetic nature when doping with Fe.
2D photonic crystal based all-optical add-drop filter consisting of square ring resonator
Materials Today: Proceedings, Volume 66, Part 7, 2022, pp. 3344-3348
In this paper, using Plane Wave Expansion (PWE) and Finite Difference Time Domain (FDTD) methods, an all optical add-drop filter (ADF) is designed and simulated. It has two defect waveguides (BUS and DROP) and a square ring resonator in-between. The structure consists of a square lattice of infinitely long dielectric circular rods of refractive index embedded in air. The total footprint of the proposed structure is merely . The backward dropping efficiency of the designed ADF is at wavelength , with transmission efficiency and quality factor equal to and respectively. The effect of variation of lattice constant Radius of the rods and Refractive index on the performance of the ADF are also investigated. As the resonant wavelength of the ring resonator can be manipulated by manipulating the parameters of the circular rods, the proposed ADF can be set to function at desired frequencies.
Hydrogen storage capacity of vanadium functionalized [2,2]paracyclophane: A density functional theory study
Materials Today: Proceedings, Volume 66, Part 7, 2022, pp. 3360-3363
This work reports the hydrogen storage capacity and properties of V atom functionalized , paracyclophane (PCP22) using dispersion corrected density functional theory (DFT-D2) calculations. The V atom was found to be bound firmly with the PCP22 via the Dewar mechanism with a binding energy of 1.88eV. Each V atom functionalized on PCP22 can adsorbed a maximum up to 5H2 molecules with a hydrogen gravimetric density of 6.10wt%, which is fairly above the target set by US-DOE. The hydrogen molecules are adsorbed with the host material by the Kubas-type interaction with an average adsorption energy in the range of 1.02eV and 0.48eV, which was the physisorption type of adsorption. Thus, we believe that our studied system PCP22-2V can be proposed as a practically viable system for hydrogen storage at standard temperature and pressure.
First-principles discovery of novel quantum physics and materials: From theory to experiment
Computational Materials Science, Volume 190, 2021, Article 110262
Modern material science has been revolutionized by the discovery of novel topological states of quantum matter, which sheds new lights on solving long-standing scientific challenges. However, the exotic quantum phenomena are typically observable only in rare material systems under extreme experimental conditions. The search of suitable candidate materials that are able to work at ambient conditions is thus of crucial importance to both fundamental research and practical applications. Here we review our recent efforts on first-principles exploration of novel quantum physics and materials, focusing on emergent quantum phenomena induced by spin-orbit coupling and its interplay with magnetism, topology and superconductivity. The first-principles material design guided by fundamental theory enables the discoveries of several key quantum materials, including next-generation magnetic topological insulators, high-temperature quantum anomalous Hall and quantum spin Hall insulators, and unconventional superconductors. A closecollaboration with experiment not only successfully confirmed most of our theoretical predictions, but also led to surprising findings for further investigations, which greatly promotes development of the research field.
Copyright © 2022 Elsevier Ltd. All rights reserved. Selection and peer-review under responsibility of the scientific committee of the Condensed Matter Physics.