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MXene is regarded as an innovative 2D nanomaterial for energy storage applications. In this study, we calculated the structural, electronic, optical, and mechanical properties of Ti3X2 (X = C, N, P, S) MXene materials using the CASTEP simulation package based on the density functional theory. The calculated lattice parameters at zero pressure are in good agreement with the previously reported results. We also calculate the studied materials' formation energy to check the compounds' stability. The negative formation energy values suggest that Ti3X2 (X = C, N, P, S) compounds are stable and can be synthesized experimentally. The electronic properties, i.e., electronic band structures, total density of state and partial density of state, suggest that Ti3X2 (X = C, N, P, S) compounds are metallic. To understand the behavior of light scattering, we calculate the optical properties of Ti3X2 (X = C, N, P, S). The maximum reflectivity occurs at 62%, 56%, 49%, and 33% for Ti3P2, Ti3C2, Ti3N2 and Ti3S2, respectively. Optical properties also suggest the metallic nature of studied materials. Mechanical properties suggest that Ti3C2 is ductile behavior and Ti3N2, Ti3P2, and Ti3S2 are brittle behavior. [ABSTRACT FROM AUTHOR]

A series of derivatives (DOCD2–DOCD6) with D–π–A configuration was designed by substituting various efficient donor moieties via the structural tailoring of o-DOC6-2F. Quantum-chemical approaches were used to analyze the optoelectronic properties of the designed chromophores. Particularly, M06/6-311G(d,p) functional was employed to investigate the non-linear optical (NLO) response (linear polarizability ⟨α⟩, first (βtot) and second (γ tot) order hyperpolarizabilities) of the designed derivatives. A variety of analyses such as frontier molecular orbital (FMO), absorption spectra, transition density matrix (TDMs), density of states (DOS), natural bond orbital (NBO) and global reactivity parameters (GRPs) were employed to explore the optoelectronic response of aforementioned chromophores. FMO investigation revealed that DOCD2 showed the least energy gap (1.657 eV) among all the compounds with an excellent transference of charge towards the acceptor from the donor. Further, DOS pictographs and TDMs heat maps also supported FMO results, corroborating the presence of charge separation states along with efficient charge transitions. NBO analysis showed that π-linker and donors possessed positive charges while acceptors retained negative charges confirming the D–π–A architecture of the studied compounds. The λmax values of designed chromophores (659.070–717.875 nm) were found to have broader spectra. The GRPs were also examined utilizing energy band gaps of EHOMO and ELUMO for the entitled compounds. Among all the derivatives, DOCD2 showed the highest values of βtot (7.184 × 10–27 esu) and γ tot (1.676 × 10–31 esu), in coherence with the reduced band gap (1.657 eV), indicating future potentiality for NLO materials. [ABSTRACT FROM AUTHOR]

Quantized conduction achieved in layered materials offers a wide range of applications in electronics. A comprehensive analysis of electronic properties of Sr2ZrO4/TiN- and Sr2ZrO4/TaN-layered heterostructure is carried out using plane wave-based first principles calculations. To understand the origin of quantized conduction, the role of oxygen vacancies (Vos) in 2D layered Ruddleson–Popper perovskite (Sr2ZrO4) is analyzed using density of states, isosurface, and integrated charge density plots. The origin of quantized states formed near the Fermi level is proposed in terms of charge conduction layer formed at the interface. The comprehensive insight of Sr2ZrO4/TiN and Sr2ZrO4/TaN heterostructure interface is provided by shedding light on the charge redistribution from charge density and Bader charge analysis. Meanwhile, work function is calculated for the confirmation of charge conducting behavior of the two layered heterostructures. The interface of these two layered heterostructures revealed the quantized conduction phenomena which cannot be achieved with either layer alone. Stable switching achieved withaTaN electrode being an important task for robust RS and solving sneak path related problem is opening roadmap for 2D layered RRAM devices. [ABSTRACT FROM AUTHOR]

Resistive switching (RS) performances had prodigious attention due to their auspicious potential for data storage. Oxide-based devices with metal insulator metal (MIM) structure are more valuable for RS applications. In this study, we have studied the effect of divalent (nickel) as well as trivalent (aluminum) dopant without and with oxygen vacancy ( V o) in hafnia ( HfO 2) -based resistive random-access memory (RRAM) devices. All calculations are carried out within the full potential linearized augmented plane-wave (FP-LAPW) method based on the WIEN2k code by using generalized gradient approximation (GGA) and generalized gradient approximation with U Hubbard parameters (GGA+U) approach. The studies of the band structure, density of states and charge density reveal that HfNiO2+Vo are more appropriate dopant to enhance the conductivity for RRAM devices. [ABSTRACT FROM AUTHOR]

With a hexagonal (honeycomb) network of mono-layered carbon atoms, graphene has demonstrated outstanding electronic properties. This work describes the impact of deliberately introduced single, double and triple carbon vacancies in grapheme monolayer. In addition, these carbon vacancies were then substituted with gold atoms and their influence on the electronic properties of the two-dimensional (2D) graphene layers was investigated. In this regard, a first principle calculation was performed to examine electronic properties and formation energy of 2D graphene layer by applying density functional theory (DFT). Introduction of such defects appeared to increase the stability of the graphene sheet as confirmed by formation energy calculations. Moreover, decrease of formation energy was noticed to be significant with an increase in the number of defects. Band structure calculations described the shifting of localized states from valance to conduction bands which caused the transformation of semiconducting behavior into metallic one on the filling of carbon vacancies by gold atoms. Comparing this behavior with that of partial density of states (PDOS) it was noted that a lot of states existed in the valance band in the case of C-vacancies yielding charge free region around the vacancy. On the other hand, filling of C-vacancies by gold generated a large number of energy states in the conduction band illustrating the accumulation of charges near gold atom. Width of the peak across the Fermi level indicated the accumulative energy of electron to be almost 0.15 eV. These calculated DOS and PDOS demonstrated metallic like behavior of the graphene monolayer with typical defect states. [ABSTRACT FROM AUTHOR]

In the present work, we have theoretically investigated the structural, electronic and optical characteristics of Mo 1−x M x O 3 (M = Zr, Y, co-doped (ZrY)) for Optoelectronic Resistive Random-Access Memory (ORRAM) devices and associated applications. Density functional theory within Heyd-Scuseria-Ernzerhof (HSE06) functional has been employed to better estimate optoelectronic parameters. The structural outcomes, findings of the energy band structure, spin resolved total density of states (TDOS), three dimensional iso-surface electron charge density, electron localization function and Bader charge analysis unveil thatMo 1−x (ZrY) x O 3 is comparatively more suitable composite with enhanced charge conductance for ORRAM devices. The partial density of states (PDOS) and Bader charge analysis results reveals that noticeable orbital contribution of the constituent atoms mainly in increasing conductivity through hybridization. Formation energy and phonon calculations confirmed that studied structures are stable. The photo absorption behavior shows that Mo 1−x (ZrY) x O 3 can absorb a broad electromagnetic radiations wavelength range from ultraviolet (UV) to infrared (IR) coherent with the charge conduction property which has been found a most fitted candidate for ORRAM and associated applications. [ABSTRACT FROM AUTHOR]

Resistive random-access memory (RRAM) also referred as memristors are considered a critical component of nano-electronics. In this first principle study we presented a polaron related model. We revealed polaron; a conducting species in mediating resistive switching (RS) mechanism in anatase polymorph of TiO 2 bulk based memristors. We examined polaron formation after substitution of silver (Ag), copper (Cu) and nickel (Ni) in place of titanium (Ti) atom. Influence of charge addition (q- and q--), charge removal (q+ and q++) and neutral (q0) states of doped system on polaron based conducting filaments are also explored. Various values of formation energy indicated the influence of charged state variation on conductivity of the three doped systems. Findings of iso-surface charge density plots indicated polaron formed around the substitutional dopants characterized by localized states in band gap region of density of states (DOS). Presence of localized state in band gap region that confirm the achievement of RS mechanism in these doped systems. Our results predicted Cu as a best substitutional dopant for polaron as a conducting species for RS mechanism. Integrated charge density plots also confirmed these results. Interstitially doped Ag, Cu and Ni doped TiO 2 systems with different charged states showed the conducting filaments formed for RS mechanism with no polaron formation. This study suggests that charged states tuned polaron in substitutional doped TiO 2 will allow to construct conducting pathway for polaronic RS mechanism in nanoelectronics beyond RRAM. • Polaron mediated RS mechanism is studied in TiO 2 anatase phase by the doping of Ag, Cu and Ni substitutionally as well as interstitially. • Tuning of polaron with various charged states (q0, q+, q++, q- and q--) of substitutionally doped TiO 2 anatase has been explored to be helpful for achieving better ON/OFF switching ratio. • The Cu sub TiO2 anatase is found to be best for RS mechanism as conduction bridge random accesses memory (CBRAM) devices with different charge states. • Substitutional dopants with q + states are found to be more stable as compared to interstitially. • No polaron formation is observed by interstitial dopants in TiO2 anatase with various charged states. [ABSTRACT FROM AUTHOR]

In the present study, we have focused to investigate the structural, electronic and optical properties of transition metal (TM) doped HfO 2 i.e; Hf 1-x TM x O 2 (TM = Co, Ni, Zn, x = 12.5%) using the Full Potential Linearly Augmented Plane Wave (FP-LAPW) based on the density functional theory (DFT). Perdew-Burke-Ernzerhof - Generalized Gradient Approximation (PBE-GGA) has been used as an exchange correlation potential. In addition, Tran-Blaha modified Becke-Jahnson exchange potential approximation (TB-mBJ) has been employed to calculate improved electronic properties. The later approach better estimates the values of the electronic band gap much closer to the values of band gap calculated experimentally. The studies of the band structure, density of states and charge density reveal that Co-doped HfO 2 is more appropriate dopant to enhance the conductivity for resistive random accesses memory (ReRAM) devices. The results from partial density of states (PDOS) disclose the facts that localized energy states, i.e., TM-3 d and O-2 p have contributed mainly in increasing conductivity through hybridization. The optical analysis depicts that Hf 1-x Co x O 2 can absorb a wide ultra violet (UV) range of electromagnetic radiations in line with the electronic behavior which has been found a most suitable candidate for ReRAM/optoelectronic memristors and other allied devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • Superalkalis doped bowel shaped silicon carbide complexes are studied via DFT method. • All complexes have electronic and thermodynamic stability. • First hyperpolarizability (β o) has increased up to 5979.99 au. • Superalkalis doping remarkably tunned the NLO response of all complexes. • Electronic excitation between superalkali and nanocluster is responsible for enhancement of NLO response. In the current study, the effect of superalkalis (Li 3 O, Na 3 O, and K 3 O) doping over bowl shaped silicon carbide (b- SiC) for geometrical, electronic and nonlinear properties has been investigated using DFT theory. The results revealed that doped b- SiC nanoclusters possess high thermodynamic stability as revealed from interaction energy up to −165.85 kcal/mol. The frontier molecular orbitals illustrate the occupation of electronic density in orbitals. Natural bond orbital charge analysis confirms the charge transfer from superalkalis to the b- SiC nanocluster. Furthermore, the electronic properties are rationalized from total density of states spectra. The highest first hyperpolarizability value (5979.99 au) is observed for isomer O of K 3 O@ b- SiC complexes. The electronic excitation is analyzed through UV–VIS analysis. Two-level model describing the internal factors responsible for enhancement of NLO response is also studied. The present work gives a guideline for the synthesis of nonlinear optical materials with greater efficiencies which can be used as building blocks in the modern world of optoelectronics. [ABSTRACT FROM AUTHOR]

The structural, electronic and magnetic properties of Cr-based MgSe in zinc blende phase have been investigated by employing the full-potential linear augmented plane waves plus local orbitals (FP-LAPW+lo) method within the spin-polarized density functional theory (DFT). According to our findings, Mg 1− x Cr x Se exhibits a half-metallic characteristic, where the ferromagnetic state is more favorable than the antiferromagnetic state. The band structure results of half-metallic Mg 1− x Cr x Se system for x =0.25, 0.50 and 0.75 show 100% spin-polarization at the Fermi level ( E F ). The total magnetic moment is 4 μ B which is mainly due to the Cr-3 d states at the Fermi level ( E F ). Our results indicate the presence of small magnetic moments arising from the other non-magnetic atoms as well. We also calculated the spin dependent charge densities to understand the bonding nature of the system. [ABSTRACT FROM AUTHOR]

• We propose Pt/a-Ta 2 O 5 /TiN memristor device for hardware driven neuromorphic. • Increased and decreased conductivity can be observed by potentiation and depression. • Theoretical confirmation of this interfacial layer is also provided by charge transportation phenomena. • Design the single layer neural network for MINIST handwritten pattern recognition. • Integrated charge density plots depicted charge transfer mechanism. [Display omitted] Internet of things and big data demand the development of new techniques for memory devices going beyond conventional ways of memorizing and computing. In this work, we fabricated a Pt/a-Ta 2 O 5 /TiN resistive switching memory device and demonstrated its resistive and synaptic characteristics. Firstly, X-ray photoelectron spectroscopy (XPS) of a-Ta 2 O 5 /TiN analysis was conducted to determine elemental compositions of a-Ta 2 O 5 /TiN and TiON interfacial layer between a-Ta 2 O 5 and TiN layer. Repetitive bipolar resistive switching was achieved by a set at a negative bias and a reset at a positive bias. Moreover, its biological potentiation and depression behaviors were well emulated by applying a repetitive pulse on the device. For deep understanding of this device's properties based on materials, oxygen vacancies, and stack engineering, theoretical calculations were performed employing Vienna ab-initio simulation Package (VASP) code. All calculations were carried out using PBE and GGA+ U method to obtain accurate results. Work function difference between electrodes provided a localized path for forming a V o based conducting filament in a-Ta 2 O 5. Iso-surface charge density plots confirmed the formation of intrinsic V o based conducting filaments in a-Ta 2 O 5. These conducting filaments became stronger with increasing concentration of V o s in a-Ta 2 O 5. Integrated charge density, density of states (DOS), and potential line ups also confirmed that V o was responsible for charge transportation in a-Ta 2 O 5 based RRAM devices. Experimental and theoretical results confirmed the formation of TiON layer between a-Ta 2 O 5 and active electrode (TiN), suggesting that the bipolar resistive switching phenomenon of the proposed device was based on oxygen vacancy (V o). [ABSTRACT FROM AUTHOR]

The mechanical, magnetic and thermoelectric properties of spin polarized XGaO 3 (X = Sc, Ti, Ag) perovskite oxides in cubic phase have been investigated using LDA + U functional through ab -initio study based on density functional theory (DFT) in the framework of WIEN2K simulation code. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) technique along with PBE-GGA functional have been used to optimize the systems and determining exchange-correlation potential. However, in order to address on-site self-interactions error and overcome limitations of PBE-GGA functional, LDA + U has been employed because Hubbard parameter 'U' is found an appropriate remedy to consider on-site self-interactions, and to calculate improved electronic energy band gap. All spin polarized band structures reveal indirect band gap with different energies E g (eV) such as ↑ ↓ 0.98 eV for ScGaO 3 , ↑ 1.05 eV and ↓ 1.70 eV for TiGaO 3 , ↑ 1.13 eV and ↓ 2.19 eV for AgGaO 3. Thus, all compounds are semiconductor in nature. The analysis of spin polarized total and partial density of states unveil that ScGaO 3 is non-magnetic material, whereas, TiGaO 3 and AgGaO 3 are characterized by strong exchange splitting of 3 d (Ti) and 4 d (Ag) states with significant spin magnetic moments, i.e., 1.0002 μ B and −2.0002 μ B , respectively. The elastic constants, i.e., Bulk, Young and Shear moduli, Poisson's coefficient, Anisotropy factor, Pugh's ratio, Cauchy pressure and melting temperature are calculated through Viogt-Reuss-Hill approximation. The thermoelectric response of the considered perovskites has been determined through semi-classical Boltzmann transport theory in the framework of BoltzTraP simulation code. Basic understandings of the mechanical, magnetic and thermoelectric properties of these compounds are studied for the first time in this manuscript. Image 1 • LDA + U functional better estimates band gap energy by considering on-site columbic interactions. • The studied compounds belong to semiconductor category. • TiGaO 3 and AgGaO 3 exhibit ductile nature, while, ScGaO 3 is brittle material. • ScGaO 3 is non-magnetic, whereas, TiGaO 3 and AgGaO 3 have significant spin magnetic moments. • The thermoelectric characters are elucidated as function of temperature. [ABSTRACT FROM AUTHOR]