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A theoretical study to investigate the electronic, optical and structural properties of sodium-based cubic fluoro-perovskite NaXF3 (where X = Ca, Mg, Sr, Zn), using density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) code with ultra-soft pseudo-potential USP plane wave and Perdew Burke Ernzerhof (PBE) exchange-correlation functional of Generalized Gradient Approximation (GGA), is reported. All of these compounds are found to be in a stable shape with a cubic pm3m structure, according to the findings. The results we discovered are consistent with the data that is already available. Calculations of the electronic band structure show that NaCaF3, NaMgF3 and NaSrF3 have a direct and NaZnF3 has an indirect band gap. Partial density of states (PDOS) and total density of states (TDOS) confirm the degree of electron localization in various bands. All four compounds' optical transitions were investigated by fitting the dispersion relation for the hypothetical dielectric function scale to the corresponding peaks. NaZnF3 is semiconductor while the NaCF3, NaMgF3 and NaSrF3 compounds have insulating behavior. The hypothetical part dispersion of the dielectric function reveals its wide range of energy transparency. As a result, it's possible that these materials may be used in optoelectronics to absorb ultraviolet light.

In this study, three chalcone derivatives with a basic skeleton of [1,100-biphenyl]-4-yl)-3-(3-nitrophenyl)prop-2-en-1-one are investigated. The basic skeleton was modified with the addition of three-terminal groups including hydrogen (1), methyl (2), and methoxy group (3). Using CASTEP Module, the optoelectronic properties are evaluated. The solid-state geometries of these systems are explored within the periodic boundary conditions (PBC). Among these systems, system 3 is found much better in terms of electron transport and optical properties such as dielectric function, absorption, conductivity, reflectivity, loss function, and refractive index. System 3 showed a higher dielectric function value about 3.7 at 1.8 eV thereby absorption 6.9 × 104 cm−1 at 300 nm and conductivity 1.2 fs−1 at 3.5 eV in the (0 0 1) plane. Furthermore, system 3 exhibited a high reflectivity and loss function in the (0 1 0) plane. Electronic band structure, the density of state, and electronic coupling analysis also reveal that system 3 has a potential application in charge transport devices. The study of electronic couplings that dominate the slowest electron hopping in a potential conductive path is roughly four to ten times larger for the holes than for the electrons. The transport pathways in systems 1 and 2 are 2D, while 1D in system 3. The bottleneck rate for electron transport is expected to be ~25 faster for system 3 than the other systems. This system 3 shows an excellent potential both at molecular and bulk levels for efficient charge transport material.

Ba(Sn, Ti)O3 (BSnTO) is an excellent functional material that can be utilized for its high electrocaloric effect, high pyroelectric effect, and good photovoltaic characteristics. The current report is based on a combined experimental and theoretical study of ferroelectric Sn-doped BaTiO3 ceramic. The sample was successfully synthesized via the solid-state sintering method. The phase purity was verified by the XRD measurements and subsequent Rietveld refinement. The sample showed good ferroelectric and dielectric properties at room temperature. Specifically, the temperature-dependent phase transition behavior was studied with dielectric measurements. The band structure, the density of states, and optical properties were calculated using the CASTEP code. Various optical constant as a function of energy was calculated and the underlying physics is explored.

The structural, electronic, vibrational and optical properties of TbMn2O5 and Tb2MnCoO6 have been studied by using density functional implemented into CASTEP and GULP codes. The geometry optimization is achieved using PBE-functional in CASTEP code. So far as, the structure is optimized using Buckingham potential through GULP code. The calculated lattice constants for TbMn2O5 and Tb2MnCoO6 are found to be a = 6.973 A, b = 8.638 A, c = 6.097 A and a = 5.559 A, b = 7.415 A, c = 5.182 A, respectively in the orthorhombic phase of these crystal structures. The electronic band structure as well as density of states of both structures unveils that the studied materials belong to semi-metallic family. Force constant matrix related to force field methods is used to calculate the phonons of the studied materials. Phonon dispersion and vibrational density of states (VDOS) are plotted to calculate the vibrational modes. In addition, infrared and Raman spectroscopy have been performed to characterize modes of the vibrations. The calculated modes of vibrations of TbMn2O5 demonstrate an excellent agreement with available experimental results. Finally, the optical behavior of TbMn2O5 and Tb2MnCoO6 has been investigated using Kramer-Kronig relations in terms of dielectric constant, reflectivity, absorption coefficient and refractive index in the frequency range 0–700 cm-1.

A theoretical study to investigate the electronic, optical and structural properties of sodium-based cubic fluoro-perovskite NaXF3 (where X = Sr, Zn), using density functional theory (DFT) based CASTEP (Cambridge Serial Total Energy Package) code with ultra-soft pseudo-potential USP plane wave and Perdew Burke Ernzerhof (PBE) exchange-correlation functional of Generalized Gradient Approximation (GGA), is reported. The findings show that both compounds are in a stable form with a cubic structure. The calculated elastic constants also meet the mechanical stability criteria. NaSrF3 is brittle, while NaZnF3 is ductile, according to Pugh's criteria. The electronic band structure calculations reveal that NaSrF3 has a direct and NaZnF3 has an indirect band gap. The finding of band gap is agreed well with the data that is already available. The degree of localized electrons in different bands is confirmed by partial density of states (PDOS) and total density of states (TDOS). By fitting the dispersion relation for the hypothetical dielectric function scale to the corresponding peaks, the optical transitions in both compounds were investigated. Both materials are insulators at 0 K and semiconductor at high temperature. However, the dielectric function's imaginary component dispersion exposes its broad range of energy transparency. As a result, it can be inferred that these materials could be used to capture the ultraviolet region in optoelectronics.

In this study, the effects of vacancies in wurtzite AlN (0001) and (000 1 ( — ) ) surfaces were investigated by performing CASTEP calculations in Materials Studio software. In particular, we comparatively analyzed the electronic structure, magnetism, and partial optical properties of AlN with surface vacancies. The results show that after introducing a vacancy, the band gap of the systems became zero, which represented a metallic characteristic. In addition, both the vacant (0001) and (000 1 ( — ) ) surfaces as well as their corresponding systems exhibited non-magnetic. Contrastingly, the original systems with an intact (0001) or (000 1 ( — ) ) surface were ferrimagnetic. Finally, it was found that the presence of the vacancy did not have any evident impact on the absorption and reflection of the AlN systems. Compared with the (0001) system, the (000 1 ( — ) ) one had greater maximum absorption coefficient and maximum reflectivity.

The g-C3N4 nanosheets with N-defects were fabricated by a sample oxidative reaction via H2O2, which can generate hydroxyl radical (•OH) to destruct the bonds of g-C3N4. The existence of •OH was confirmed by PL (photoluminescence spectroscopy) and HPIC (high-pressure ion chromatography). The N-defects were confirmed by the concentration of nitrate in solution increasing from 1.04 to 4.65 mg/L. Further, the source of N-defects was speculated as the destruction of C N C due to its lower bond-energy and decreasing ratio of C N C (CASTEP, XPS). As a result, the obtained N-defective g-C3N4 improved the photocatalytic degradation efficiency to Methylene blue (MB) from 53.1% (g-C3N4) to 100.0% under visible light. This result was ascribed by the N-defect narrowed the bandgap from 2.71 to 2.67 eV, accelerated the separation and transfer of photo-generated carriers. This work provides a new strategy to construct defects in a catalyst improving photocatalytic performance.

The effect of different cations (Ca2+, Mg2+, Ba2+ and Sr2+) adsorption on carbonate type scaling formation was studied by using CASTEP and Forcite module based on density functional theory and molecular dynamics, respectively. By calculating the adsorption energy of cations adsorbed on four adsorption sites (top, hollow, short-range bridge and long-range bridge) of (2 × 1 × 1)CaCO3 (1 –1 0) surface, the most stable adsorption site was determined. On this basis, the banding mechanism of O atom and cation was studied by analyzing the state density of different cations adsorbed model. It has been shown that the Mg2+ cation adsorbed at top site of O atom on CaCO3(1 –1 0) surface was the most stable one according to the adsorption energy calculation results. Under the condition of multiple type of cations co-existence at the same ionic concentration, Mg2+ and Ba2+ would preferably combined with CO32– to form magnesium carbonate and barium carbonate scaling, causing the crystal growth process of calcium carbonate scaling inhibited. The converse is equally true that the existence of Sr2+ is more conducive to the calcium carbonate scaling crystal growth. The radial distribution function analysis indicated that the bonding strength between Mg2+ and O atom on CaCO3 (1 –1 0) surface is the largest, weakening followed Ba2+, Ca2+ and Sr2+ successively. Density of state study indicated that adsorption of Mg2+ cation on CaCO3 (1 –1 0) surface is mainly due to the interaction between 2p orbit of O atoms and 3s orbit of Mg2+ cation.

It was reported that a scanning tunneling microscopy (STM) study observed the adsorption geometry of a water monomer and a tetramer on NaCl(100) film. Based on first-principles density functional theory (DFT), the adsorption behavior of water on the NaCl surface was simulated with CASTEP code. The results showed that the water monomer almost lay on the NaCl(001) surface with one O–H bond tilted slightly downward. This was quite different from the STM observations. In fact, the experimental observation was influenced by the Au(111) substrate, which showed an upright form. A recent report on observations of two-dimensional ice structure on Au(111) substrate verified our simulations. However, the water tetramer formed a stable quadrate structure on the surface, which was consistent with observation. The intermolecular hydrogen bonds present more strength than surface adsorption. The simulations presented a clearer picture than experimental observations.

The structural, electronic, and optical properties of an amorphous SiO2 (a-SiO2) model is investigated by using first-principles calculation. Most research works used beta-cristobalite glass structure as a reference to amorphous silica structure. However, only the electronic properties were been presented without any link towards the optical properties. Here, we demonstrate simultaneous electronic and optical properties, which closely matched to a-SiO2 properties by generating small sample of amorphous quartz glass. Using the Rietveld refinement, amorphous silica structure was generated and optimized using density functional theory in CASTEP computer code. A thorough analysis of the amorphous quartz structure obtained from different thermal treatment was carried out. The structure of amorphous silica was validated with previous theoretical and experimental works. It is shown that small sample of amorphous silica have similar structural, electronic and optical properties with a larger sample. The calculated optical and electronic properties from the a-SiO2 glass match closely to previous theoretical and experimental data from others. The a-SiO2 band gap of 5.853 eV is found to be smaller than the experimental value of ~9 eV. This is due to the underestimation and assumption made in DFT. However, the band gap value is in good agreement with the other theoretical works. Apart from the absorption edge at around 6.5 eV, the refractive index is 1.5 at 0eV. Therefore, this atomic structure can served as a reference model for future research works on amorphous structures.

A model of undefected and defected amorphous SiO2 has been constructed from Rietveld Refinement to investigate the effect of defect structure to its properties. Atomic level study for both structure were carried out using plane-wave pseudo potential by density functional theory. A new electrons trapping energy level appears within the 5.853eV band gap of a-SiO2 for oxygen-excess defected structure. This defect energy level reduces as more number of excess oxygen atoms was added to the structure of a-SiO2. A spectral emission at 388nm from SiO2 glass excited with 350nm (200mW) laser demonstrates the existence of the defective states in the structure in trapping electron at 3.273eV energy level.

Diisopropylammonium bromide (DIPAB) can be crystallized either in an orthorhombic (P212121) or in a monoclinic (P21) structure at room temperature depending on synthesis conditions. The non-polar orthorhombic structure exhibits a subtle, irreversible transformation into the ferroelectric monoclinic-II (m-II) phase above ~ 421 K. At a slightly higher temperature of 426 K this m-II (P21) phase reversibly transforms into a disordered, paraelectric monoclinic-I (P21/m) structure. We synthesized DIPAB in the orthorhombic structure, heated it to obtain the m-II phase and carried out a systematic study of their Raman and IR spectra. We obtained the phonon irreducible representations from factor group analysis of the orthorhombic and m-II structures based on the reported structural information. DIPAB is an organic molecular crystal, and the vibrational spectra in the intramolecular region (200–3500 cm− 1) of the two different phases are identical to each other, indicating weak inter-molecular interactions in both crystalline structures. In the low wavenumber region (10–150 cm− 1) the Raman spectra of the two phases are different due to their sensitivity to molecular environment. We also carried out first principles calculations using Gaussian 09 and CASTEP codes to analyze the vibrational frequencies. Mode assignments were facilitated by isolated molecule calculations that are also in good agreement with intramolecular vibrations, whereas CASTEP (solid state) results could explain the external modes.

We studied the structural, elastic, electronic and optical properties of the orthorhombic NaMgH 3 , NaMgH 2 F, NaMgHF 2 and NaMgF 3 compounds. By means of the self-consistent CASTEP code, pseudopotentials, density functional theory in the LDA and GGA approximations, basic physical properties, such as lattice constant, shear modulus, elastic constants ( C ij ) and optical constants are computed. This study includes elastic parameters of mono and poly-crystalline aggregates. Derived elastic constants, such as bulk, Young's and Shear modulus, Poisson coefficient, Debye temperature and brittle/ductile behavior are estimated with the polycrystalline approach, using Voigt–Reuss–Hill theory. The calculations show that the orthorhombic Pnma structures are mechanically and dynamically stable in the pressure range (0–20 GPa). The calculated density of states shows that the orthorhombic compounds are insulators.

In this study, the CASTEP program based on the density functional theory was used to investigate the ability of the outside wall of a N-doped CNT (carbon nano tube) bus-bar to adsorb Fe (iron) atoms, under a deformation of the superlattice structure. The calculation results show that the formation energy of the new structure is negative, satisfying the energy conditions of stable existence. The energy of the adsorbing Fe atoms at each point has been significantly increased, indicating the improvement of the bonding strength between the CNTs and the Fe substrate. The doping of electron-rich N atoms makes the density of states at the Fermi level increase, which makes it easier to react with external matter. The Mulliken charge number and the population number show that N atoms have a stronger ability to adsorb electrons, so the strength of the bond between Fe and N is higher. Small amounts of linear tension and compression will not affect the ability of the new structure to adsorb Fe atoms. However, the adsorption abilities drop quickly after the deformation amplitude reaches its critical value, and the adsorption energies become more sensitive to the tensile deformation. The ionic bond of Fe-N is a key factor for raising the ability of the N-doped CNT bus-bar to adsorb Fe atoms.

We have predicted a new crystal MgRhO 3 in the metal oxide family with a SrTiO 3 type structure by performing ab-initio calculations implemented within the CASTEP code. This present study includes the structural parameters, band structure, density of states, bonding characteristics and elastic parameters of the MgRhO 3 perovskite. The detailed study on the mechanical properties ensures the mechanical and dynamical stability of MgRhO 3 in nature. MgRhO 3 is ductile in manner and shows anisotropy characteristics. This new metal oxide exhibits metallic conductivity and complex bonding with covalent and ionic characteristics.

In this work, the interfacial structure of a linear friction welded (LFWed) Fe/Ni joint was studied using CASTEP based on first principles. Calculations clearly show that the Fe(100)/Ni(100) structure is the most stable bonding structure at the Fe/Ni interface, where 3d orbital electrons have a significant contribution to the interface bond and the Fe(3d)-Ni(3d) bond displays a strong covalent bonding effect. Transmission electron microscopy and energy-dispersive X-ray spectroscopy were used to evaluate the LFWed Fe/Ni interface. The experimental results show that the stable bonding structure appears at the weld edge and the orientation is (100)Fe//(100)Ni, [010]Fe//[011]Ni, as predicted by calculations. While at the weld center orientation is (011)Fe//(10 1 - )Ni, [100]Fe//[11 2 - ]Ni due to lattice distortion.

In this work, we report the results of a detailed structural study of a promising bioceramic material silicocarnotite Ca 5 (PO 4 ) 2 SiO 4 (SC) synthesized from mechanochemically treated nanosized silicon-substituted hydroxyapatite by annealing at 1000 °C. This novel synthetic approach represents an attractive and efficient route towards large-scale manufacturing of the silicocarnotite-based bioceramics. A combination of solid-state nuclear magnetic resonance (NMR), powder X-ray crystallography and density function theory (DFT) calculations has been implemented to characterize the phase composition of the prepared composite materials and to gain insight into the crystal structure of silicocarnotite. The phase composition analysis based on the multinuclear solid-state NMR has been found in agreement with X-ray powder diffraction indicating the minority phases of CaO (5–6 wt%) and residual silicon-apatite (7–8 wt%), while the rest of the material being a fairly crystalline silicocarnotite phase (86–88 wt%). A combination of computational (CASTEP) and experimental methods was used to address the anionic site disorder in the silicocarnotite crystal structure. Distorted [OPO 3 ] pyramids have appeared as an important structural motif in the SC crystal structure. The ratio between regular [PO 4 ] and distorted [OPO 3 ] tetrahedra is found between 2:1 and 3:1 based on XRD experiments and CASTEP calculations. The natural abundance 43 Ca magic angle spinning NMR spectra of silicocarnotite are reported for the first time.

This paper presents a first principles study on the effect of co-doping on various optical spectra of a zigzag single-walled carbon nanotube (SWCNT). Optical spectra of a pristine SWCNT, SWCNT co-doped with Aluminum (Al) & Phosphorus (P) and another one co-doped with Al, P and Nitrogen (N) have been calculated using density functional theory (DFT).The theory has been implemented using the Cambridge sequential total energy package (CASTEP) code available as a userfriendly module with the software ‘Material Studio’. Polarized and unpolarized light as well as light through polycrystalline media have been considered. The dependence of various spectra on the status of incident light presents a clear evidence of anisotropicity in the optical properties. Analysis of the simulated spectra involves calculation and comparison of different optical properties like dielectric function, reflectivity, refractive index, conductivity and loss function for the pristine and co-doped SWCNTs. Noticeable variations are observed in the optical properties on simultaneously doping the SWCNT with Al and P and then further introducing N atom into the structure so that it can be concluded that co-doping (simultaneous doping with different combinations of dopants) can be evolved as a novel and effective tool for tailoring the optical properties of SWCNTs as per the requirements while designing an optical device. It will prove to be highly significant for effective designing of SWCNT based sensitive optical devices for a variety of technological applications.

Element doping is an efficient strategy for tuning the electronic structure and improving the photocatalytic activity of graphitic carbon nitride (g-C3N4). Employing the density functional theory computation performed by CASTEP module, we investigated the band structures, electronic and optical properties of monolayer g-C3N4 doped with halogens (F, Cl, Br or I). First, the halogen atoms occupying the interstitial space enclosed by three tri-s-triazine units in the monolayer g-C3N4 unit cell was demonstrated to be the most stable configuration in terms of adsorption energy. On the basis of these interstitial-doped monolayer g-C3N4 systems, it is found that the introduction of halogen atoms leads to various density of states (DOS) and redistribution of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). The F atom tends to occupy the valance band and HOMO due to its extremely high electronegativity. By contrast, the Cl, Br and I atoms are involved in the conduction band and LUMO. In sum, the calculation results show that the halogen-doped monolayer g-C3N4 systems have narrowed band gap, increased light absorption and reduced work function, which are conducive to high photocatalytic activity. The conclusions presented in this work indicate the availability of halogen-doped monolayer g-C3N4 with considerable photocatalytic performance.

This paper reports the synthesis, experimental and theoretical studies of a novel inorganic-organic cocrystal energetic material: methylamine triethylenediamine triperchlorate (MT). MT is synthesized by a rapid “one-pot” method. The performance test of MT shows that it is more powerful and has lower sensitivity in comparison to the benchmark energetic material, i.e., 2,4,6-trinitrotoluen (TNT). The molecular and crystal structures of MT are determined by means of x-ray diffraction (XRD). The compound crystallizes in a monoclinic system (space group Pn) with cell dimensions a = 8.975(18), b = 17.836(4), and c = 10.455(2) A. The band structure and the density of states are calculated by an abbreviated form of the CASTEP code. The first principle tight-binding method within the general gradient approximation is used to study the electronic band structure, density of states, and Fermi energy. The results indicate that the main mechanism of cocrystallization originates from the Cl—O ···H hydrogen bonding between —ClO4 and —NH2.

Numerous materials characteristic including yttrium iron garnet (YIG) are directly dependent on its crystal structure; phase diversity. However, only a few examination of energy and its mechanism at atomistic scales was reported. In this article, a density functional theory (DFT) based calculations have been carried out to study electronic properties of cubic Y3Fe5O12 (YIG) at its known active sites; (0,0,4), (2,2,4) and (2,2,4). The density of state (DOS) these sites were presented at-19 eV to-14 eV for lower valance band and-6 eV to 0 for upper valance band. Both (0,0,4) and (0,2,4) planes shows highest possibility of cation substitution since the energy substitution are the lowest (~40 KeV). (2,2,4) plane composed of O-O interaction in which would contribute to the oxygen vacancy.

Based on first-principles method, the electron structure of porous graphene (PG) and adsorption ability of H 2 molecular on Y-decorated porous graphene are investigated using CASTEP code. It is found that the bridge of C–C bond which connects two C hexagons is favorable site for a Y atom adsorbed on the single side of PG, and six H 2 molecules can be absorbed around a Y atom with average adsorption energy of −0.297 eV/H 2 computed by GGA-PBE functional. Though two Y atoms can be stably adsorbed on the same side of one unit cell of PG, there isn’t sufficient space for H 2 absorbing around each Y atom. To improve capability of hydrogen storage, the unit cell of PG with single side should only contain one Y atom. For the case of double side of porous graphene, two Y atoms are preferably located above the center of the different C hexagon. Fourteen H 2 molecules can be absorbed on both sides of PG, and the gravimetric hydrogen storage capacity is 7.87 wt.% with the average adsorption energy of −0.23 eV/H 2 .

There are growing interests on magnetic nanowires, due to their potential applications in magnetic sensors and recording devices. In this work, we report a comparative ab-initio study based on the Density Functional Theory (DFT) of NixFe1-x nanowire periodic arrays by using atomic-orbital and plane-wave basis respectively through DMol3 and CASTEP codes. After performing the geometry optimization, we calculate the spin-polarized electronic density of states, average interatomic distance, and magnetic moments. For pure Ni nanowires (x = 1, the dependence of the magnetic moment obtained from CASTEP calculations on the cutoff energy, as well as that from DMol3 on the thermal smearing parameter is analyzed in detail. Bothab-initio calculations predict close magnetic moments for eachx, being slightly larger those of DMol3 obtained with significantly less computing cost. Finally, these DFT results are compared with experimental data and a good agreement is observed.

The optical frequency response and changes to the dielectric and optical parameters due to annealing temperature variation (200–500 °C) of sol–gel derived CuCoOx thin film coatings were investigated. The optical constants such as absorption coefficient, band-gaps, Urbach energy, complex refractive index, complex dielectric constants, optical dispersion parameters, and energy loss functions were determined from reflectance data analysis recorded in the ultraviolet to near-infrared (190–2200 nm) range. The absorption coefficient and the broadening of absorption edge (steepness parameter), energy band-gaps, Urbach energy, loss tangent and energy loss functions decreased with the increase in annealing temperatures. The refractive index displayed normal dispersion behaviors at higher frequency with the maximum value at a temperature of 500 °C. First-principles simulations, density functional theory (DFT+U) as implemented in the Cambridge Serial Total Energy Package (CASTEP), based on a cluster structure of Cu0.5Co2.5O4 system, optimized the crystalline structure and calculated the electronic structure of the framework. The calculated density of states (DOS) and associated absorption coefficient and dielectric constant results reasonably support the experimental findings.

Herein, via the first-principles density functional theory, CASTEP code, we investigated the 15 vibrational normal modes of ferroelectric hydrogen-ordered phase of ice Ic. The physical mechanism of hydrogen bond vibrations has been indicated by two type of peaks: the weak peak corresponds to two hydrogen bonds participating in the basal plane and the strong peak is composed by four hydrogen bonding vibrations for one molecule along the optic axis. The assignments of vibrational spectrum are individually conducted via the analysis of normal modes. The agreements of experimental data with the computed results manifest that the hydrogen-disordered bulk Ic may be composed by domains of a ferroelectric-ordered phase. We also predicted that the ferroelectric phase of ice Ic should show a birefringent phenomenon along the optical axis provided that a single crystal of the ferroelectric phase of ice Ic could be made.

By using a rigid dicarboxylate ligand, 4,5-di(4′-carboxylphenyl)benzene (H2L), two complexes formulated as SrL(DMF)(H2O)·(CH3CN) (DMF=N,N′-dimethylformamide) (1) and BaL(H2O)2 (2) were solvothermally synthesized and structurally characterized by single-crystal X-ray diffraction. Complexes 1 and 2 display two-dimensional (2D) layer structures. The two complexes exhibit different electrochemical and photoelectrochemical properties. Their thermal stabilities, cyclic voltammograms, UV–vis absorption and diffuse reflectance spectra and photoluminescence properties have been investigated. The band structures, the total density of states (TDOS) and partial density of states (PDOS) of the two complexes were calculated by CASTEP program. Complex 2 exhibits much higher photocurrent density than complex 1. The Mott–Schottky plots reveal that complexes 1 and 2 both are p-type semiconductors, which are in agreement with their band structure calculations.

Synthesis of Al x Ti 1-x BiO 3 (0.0 ≤x≤ 0.33) (S1-S4: x = 0.0, 0.11, 0.22, 0.33) oxides is performed by sol-gel method via nitrate-citrate route. Analysis of the powder X-ray diffraction (XRD) patterns show tetragonal unit cell with lattice parameters: a = 6.6377, 6.6398, 6.6370, 6.6366 A; c = 6.5445, 6.5391, 6.5259, 6.6583 A, respectively in S1-S4, with space group P42/mnm and Z=4. Average crystallite sizes determined by Scherrer relation are found to be in the range ~16-36, 18-50, 19-48 and 19-41 nm in S1-S4, respectively. On Rietveld refinement of unit cell structures the agreement factors are lowered to: R p = 98.28, 97.65, 98.85, 94.29 %; R wp = 97.11, 96.76, 97.92, 95.73 %; R exp = 0.09, 0.09, 0.09, 0.09 % in S1-S4, respectively. Fourier electron density mapping show irregular contours around Bi 3+ , Ti 3+ and O 2- ions due to significant ionic character in Ti-O and Bi-O bonds in the materials. Presence of hysteresis loops in the range -6 kG to +6 kG at 300 K with magnetic susceptibility values in the range 5.926 x 10 -8 - 6.461 x 10 -8 emu/gG in S1-S4 show soft ferromagnetic nature of the oxides. Density functional theory (DFT) calculations using CASTEP (Cambridge Serial Total Energy Package) programme package show energy band gap, E g , ~ 0.01-0.02 eV indicating weak semiconducting nature of the oxides. The valence band (VB) predominantly comprises O 2p, Ti 3d, Al 3p and Bi 6p orbitals, and the conduction band (CB) comprises mostly O 2p, Al 3p and Bi 6p orbitals with extension of band tails narrowing the energy band gap.