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The relative energetic stability of the structural phases of common antiferromagnetic transition-metal oxides (MnO, FeO, CoO, and NiO) within the semilocal and hybrid density functionals are fraught with difficulties. In particular, MnO is known to be the most difficult case for almost all common semilocal and hybrid density approximations. Here, we show that the meta-generalized gradient approximation (meta-GGA) constructed from the cuspless hydrogen model and Pauli kinetic energy density (MGGAC) can lead to the correct ground state of MnO. The relative energy differences of zinc-blende (zb) and rock-salt (rs) structures as computed using MGGAC are found to be in nice agreement with those obtained from high-level correlation methods like the random phase approximation or quantum Monte Carlo techniques. Besides, we have also applied the onsite hybrid functionals (closely related to DFT+U ) based on GGA and meta-GGA functionals, and it is shown that a relatively high amount of Hartree-Fock exchange is necessary to obtain the correct ground-state structure. Our present investigation suggests that the semilocal MGGAC and onsite hybrids, both being computationally cheap, as methods of choice for the calculation of the relative stability of antiferromagnetic transition-metal oxides having potential applications in solid-state physics and structural chemistry.

Sustainable materials made from recycled materials are an alternative to traditional materials (synthetic ones) and present a lower environmental impact. Due to the fact that natural fibers were successfully used to produce environmentally friendly sound adsorbing materials, biocomposites made from recycled polypropylene (PPR), feathers flour (FF) with / without compatibilizers (C) were obtained and characterized from the point of view of their acoustical behavior. Obtained materials were characterized also from the morphological and compositional point of view by scanning electron microscopy and thermal gravimetric analysis. All tested samples presented sound adsorption properties but the best results were obtained for the biocomposites with FF content of 10%-20%.

Cyclophosphamide (CP) is a cytostatic drug prescribed at large scale, which proved to induce toxic effect on ecosystems and cannot be removed by conventional wastewater treatment processes. Therefore, there is a need to test advanced degradation processes for its removal from wastewater discharges. CP photocatalytic degradation via UV-VIS irradiation was studied using a Nitrogen -doped TiO2 catalyst. The catalyst was synthesized as thin film deposited on glass substrate under nitrogen atmosphere technique. The influence of N2 flow rate and annealing temperature on the CP degradation efficiency was investigated and best photocatalytic activity was obtained for catalyst with 1.8 %wt nitrogen content, synthesized at N2 flow rate=10 sccm, annealed at 550 oC for 1 hour. Its use assure the CP degradation with a pseudo-first order rate constant of 5.262 x 10-4 s-1 and an efficiency of 98 % for an irradiation time of 120. Based on the obtained experimental results in the presence of various scavengers it was found that superoxide radicals are representing the main oxidizing reactive specie involved in CP degradation, but contribution of free hydroxyl radicals from bulk solution is also possible. Degradation intermediates were identified using LC-MS and a possible degradation pathway consisting in three conversion routes was proposed.

In this paper, two chelate resins prepared by a simple procedure were used for the removal of Cd

The semilocal form of an exchange hole is highly useful in developing non-local range-separated hybrid density functionals for finite and extended systems. The way to construct the conventional exact exchange hole model is based on either the Taylor series expansion or the reverse engineering technique from the corresponding exchange energy functional. Although the latter technique is quite popular in the context of generalized gradient approximation (GGA) functionals, the same for the meta-GGA functionals is not so much explored. Thus, in this study, we propose a reverse-engineered semilocal exchange hole of a meta-GGA functional, which only depends on the meta-GGA ingredient α (also known as the Pauli kinetic energy enhancement factor). The model is subsequently used to design the short-range-separated meta-GGA hybrid density functional. We show that the present method can be successfully applied for several challenging problems in the context of solids, especially for which the GGA based hybrid fails drastically. This assessment proves that the present functional is quite useful for materials sciences. Finally, we also use this method for several molecular test cases, where the results are also as comparative as its base semilocal functional.

The study is highlighting the possibility of modeling the properties of composite materials based on recycled polypropylene (PPR), flour feathers(FF), and compatibilizers (C). The composite materials with 10% and 20% feather flour content were mixed and processed with a two-stage extruder having four heating zones between 200-230�C, in order to obtain granules. The granules were injected in various forms to evaluate the properties. The composite materials have been evaluated for determination of melt flow index (1900C; 2.16kg), density, Charpy impact, breaking strength, elongation at break, and the dielectric behavior. The results showed that the introduction of feather flour in the polymer matrix based on PPR leads to decreased flow properties as well as physical and mechanical properties. The solution in solving these deficiencies was to use compatibility agents, that would improve these properties. The physico mechanical properties were analyzed in order to identify a composite with optimal properties for industrial application.

Photocatalytic degradation of carbamazepine (CBZ) from spiked aqueous solutions, via a UV/TiO

Connections between the Görling-Levy (GL) perturbation theory and the parameters of double-hybrid (DH) density functional are established via adiabatic connection formalism. Moreover, we present a more general DH density functional theory, where the higher-order perturbation terms beyond the second-order GL2 one, such as GL3 and GL4, also contribute. It is shown that a class of DH functionals including previously proposed ones can be formed using the present construction. Based on the proposed formalism, we assess the performance of higher-order DH and long-range corrected DH formed on the Perdew-Burke-Ernzerhof (PBE) semilocal functional and second-order GL2 correlation energy. The underlying construction of DH functionals based on the generalized many-body perturbation approaches is physically appealing in terms of the development of the non-local forms using more accurate and sophisticated semilocal functionals.

Synthetic solutions of flutamide were subject to degradation using three advanced oxidation systems, namely UV/TiO2, UV/H2O2 and UV/H2O2/TiO2. Optimum conditions and degradation kinetics has been established for all three systems. The experimental results showed that all three systems can be successfully used for flutamide degradation with efficiencies higher than 99% and that advanced oxidation processes are showing good potential for degradation of organic pollutants that cannot be suitable removed/degraded using conventional wastewater treatment processes.

This study is based to a new concept, to use maize stalk for specific sorption and recovery of Cu(II) and Fe(III) from synthetic solutions. Thus, the sorption properties of the biomass resulting from the recycling of the maize stalk that reached maturity (autumn) were studied. In the first stage, the sorption properties of the maize stalk were evaluated in batch system. Moreover, in terms of water quality improvement several key parameters that influence the sorption equilibrium were evaluated. The effect of contact time (0-120min) and cations initial concentration (investigated range: 0.05-0.4 mg/L) on biomaterial sorption capacity were assessed. Kinetic studies were performed taking into consideration the initial concentration of metallic cation. The experimental data were analyzed based on first order kinetic model, pseudo-second-kinetic model and Morris Webber kinetic model. The kinetics of sorption was in accordance with the pseudo - second - kinetic model as the correlation coefficients showed (R2=0.9940 for Cu(II) and R2=0.9999 for Fe(III)). Moreover the desorption study was evaluated with hydrochloric acid and have detected to be 63% and 89% for Cu(II) and Fe(III) when 4M HCl is used. The surface of the maize stalk loaded with Cu(II) and Fe(III) was characterized by various specific techniques such as FTIR-ATR, SEM, and TG. Experimental results revealed that cations sorption process takes place on the sorbent surface. The sorption rate of each metallic cation is controlled by the formation of chemical bonds with surface polar groups. Their presence on biomass structure, evidenced by FTIR-ATR analysis, explains the behavior of maize stalk as a weak ion exchanger acid.

The modified point charge plus continuum (mPC) model [Constantin, L. A.; Phys. Rev. B 2019, 99, 085117] solves the important failures of the original counterpart, namely, the divergences when the reduced gradient of the density is large, such as in the tail of the density and in quasi-dimensional density regimes. The mPC allows us to define a modified interaction-strength interpolation (mISI) method inheriting these good features, which are important steps toward the full self-consistent treatment. Here, we provide an assessment of mISI for molecular systems (i.e., considering thermochemistry properties, correlation energies, vertical ionization potentials, and several noncovalent interactions), harmonium atoms, and functional derivatives in the strong-interaction limit. For all our tests, mISI provides a systematic improvement over the original ISI method. Semilocal approximations of the second-order Gorling-Levy (GL2) perturbation theory are also considered in the mISI method, showing considerable worsening of the results. Possible further development of mISI is briefly discussed.

We show that accurate exchange–correlation hybrid functionals give very physically optimized effective-correlation potentials, capable of correctly describing the quantum oscillations of atoms and molecules. Based on this analysis and on understanding the error cancellation between semilocal exchange and correlation functionals, we propose a very simple, semilocal correlation potential model compatible with the exact exchange of density functional theory, which performs remarkably well for charge densities and orbital energies.

Bisphenol A (BPA) � an endocrine disruptor, degradation was studied using the following systems: UV/H2O2 and UV/H2O2/TiO2. Optimum operating conditions were established for both studied systems and experimental results showed that the two systems could be successfully used for advanced degradation of BPA achieving degradation efficiencies for BPA of 99.99% in optimum working conditions. The two systems were compared and both advantages and disadvantages of each system were identified. Nine degradation intermediates were identified for BPA degradation in UV/H2O2/TiO2 system and a possible degradation pathway was proposed.

The objective of the present study was to evaluate the performance of the ultrafiltration process on the recovery of collagen solution constituents at laboratory scale, using a tangential flow filtration, with flat regenerated cellulose membrane (5000 Da). Also permeate flows were evaluated along with the physicochemical characteristics of the concentrates, the permeates and feed solutions. The regenerated cellulose membranes were morphological studied by electron microscopy and characterized by water solutions permeation at different pressures. Keywords: collagen, concentration, protein, purification, ultrafiltration

Accurate prediction of the water properties from a low-cost ab initio method is still a foremost problem for chemists and physicists. Although density functional approaches starting from semilocal to hybrid exchange-correlation functionals are tested, they are not efficiently performing for all the properties together, especially considering energies, conformal ranking, structures, and dynamics of water. Also, the inclusion of the long-range van der Waals interaction does not improve the ordering stability of isomers. However, relying on the simple revision of the Tao-Mo (revTM) semilocal meta-generalized gradient approximation exchange-correlation functional, we demonstrate that many properties of the water clusters and ice phases can be accurately predicted. A consistent improvement over several popular ab initio methods is achieved, indicating the accuracy of this method for describing hydrogen bonding of water.

In this paper, two chelate resins prepared by a simple procedure were used for the removal of Cd2+, Ni2+, Cu2+, and Pb2+ (M2+) from aqueous solutions. Amberlite IRA 402 strongly basic anion exchange resin in Cl− form (IRA 402 (Cl−) together with Amberlite XAD7HP acrylic ester co-polymer (XAD7HP) were functionalized with chelating agent Direct red 23 (DR 23). The chelate resins (IRA 402-DR 23 and XAD7HP-DR 23) were obtained in batch mode. The influence of interaction time, pH and the initial concentration of DR 23 solution was investigated using UV-Vis spectrometry. The time necessary to reach equilibrium was 90 min for both resins. A negligible effect of adsorption capacity (Qe) was obtained when the DR 23 solution was adjusted at a pH of 2 and 7.9. The Qe of the XAD7HP resin (27 mg DR 23/g) is greater than for IRA 402 (Cl−) (21 mg DR 23/g). The efficiency of chelating resins was checked via M2+ removal determined by the atomic adsorption spectrometry method (AAS). The M2+ removal by the IRA 402-DR 23 and XAD7HP-DR 23 showed that the latter is more efficient for this propose. As a consequence, for divalent ions, the chelated resins followed the selectivity sequence: Cd2+ > Cu2+ > Ni2+ > Pb2+. Additionally, Cd2+, Cu2+ and Ni2+ removal was fitted very well with the Freundlich model in terms of height correlation coefficient (R2), while Pb2+ was best fitted with Langmuir model for IRA 402-DR 23, the Cu2+ removal is described by the Langmuir model, and Cd2+, Ni2+ and Pb2+ removal was found to be in concordance with the Freundlich model for XAD7HP-DR 23. The M2+ elution from the chelate resins was carried out using 2 M HCl. The greater M2+ recovery from chelating resins mass confirmed their sustainability. The chelate resins used before and after M2+ removal by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis were evaluated.

We show that the reduced, dimensionless Yukawa potential ${y}_{\ensuremath{\alpha}}$ can be employed as an important ingredient in the construction of the exchange and correlation energy functionals. A functional based on ${y}_{\ensuremath{\alpha}}$ provides a better description of the exchange and correlation linear response functions of the homogeneous electron gas, not only at small wave vectors, where gradient expansions are correct, but also at large wave vectors, where semilocal exchange and correlation functionals fail badly. Moreover, the ${y}_{\ensuremath{\alpha}}$ ingredient gives a realistic description of the exchange energy and potential at the nuclear cusp and the inner atomic core, where the semilocal ingredients (i.e., the reduced gradient and Laplacian of the density) are not suitable, causing divergence of the potential. Thus, the ${y}_{\ensuremath{\alpha}}$ ingredient can be attractive for the development of various exchange-correlation functionals.

In the density functional theory, dispersion corrected semilocal approximations are often used to benchmark weekly interacting finite and extended systems. Here, the focus is on providing a broad overview of the performance of D3 dispersion corrected revised Tao-Mo (revTM) semilocal functionals [A. Patra et al., J. Chem. Phys. 153, 084 117 (2020)] for thermochemistry and kinetics of molecules, molecular crystals, ice polymorphs, metal-organic systems, atom/molecular adsorption on solids, water interacting with nano-materials, binding energies of layered materials, and properties of weekly and strongly bonded solids. We show that the most suitable "optimized power" function for the revTM functional needs a modification to make it suitable for properties related to the diverse nature of finite and extended systems. The present work is an extension of the previously proposed revTM+D3 method with the motivation to design and benchmark the dispersion corrected cost-effective method based on this semilocal approximation. We show that the revised revTM+D3 functional provides various general purpose molecular and solid properties with the closest to experimental findings than its predecessor. The present assessment and benchmarking can be practically useful for performing cost-effective method based simulations of various molecular and solid-state properties.

Accurate theoretical prediction of the band offsets at interfaces of semiconductor heterostructures can often be quite challenging. Although density functional theory has been reasonably successful to carry out such calculations, efficient, accurate semilocal functionals are desirable to reduce the computational cost. In general, the semilocal functionals based on the generalized gradient approximation (GGA) significantly underestimate the bulk bandgaps. This, in turn, results in inaccurate estimates of the band offsets at the heterointerfaces. In this paper, we investigate the performance of several advanced meta-GGA functionals in the computational prediction of band offsets at semiconductor heterojunctions. In particular, we investigate the performance of r2SCAN (two times revised strongly constrained and appropriately normed functional), rMGGAC (revised semilocal functional based on cuspless hydrogen model and Pauli kinetic energy density functional), mTASK (modified Aschebrock and Kümmel meta-GGA functional), and local modified Becke–Johnson exchange-correlation functionals. Our results strongly suggest that these meta-GGA functionals for supercell calculations perform quite well, especially, when compared to computationally more demanding GW calculations. We also present band offsets calculated using ionization potentials and electron affinities, as well as band alignment via the branch point energies. Overall, our study shows that the aforementioned meta-GGA functionals can be used within the density functional theory framework to estimate the band offsets in semiconductor heterostructures with predictive accuracy.

We investigate the behavior of three-dimensional 3D exchange energy functional of density-functional theory in anisotropic systems with two-dimensional 2D character and 1D character. The local density approximation (LDA), the generalized gradient approximation (GGA), and the meta-GGA behave as functions of quantum well width. We use the infinite-barrier model (IBM) for the quantum well. In the first section, we describe the problem of three-dimensional exchange functional, in the second section we introduce the quasi-2D IBM system, in the third section we introduce the quasi-1D IBM system. Using that an exact-exchange functional provides the correct approach to the true two-dimensional limit, we want to show that the 2D limit can be considered as a constraint on approximate functionals. For the 1D limit case we also propose a new functional obtained with methods completely similar to those of 2D limit.

The degradation of some toxic pollutants like chlorobenzenes, nitrobenzene and 4-chloroaniline in various advanced oxidation system such as: UV/ H2O2, UV-VIS/Fe-TiO2 and UV-VIS/TiO2/ H2O2 were studied. The influence of working conditions (pH0, H2O2 dose, photocatalyst dose, pollutant initial concentration and irradiation time) on pollutant degradation rate constant and efficiency were investigated. For any studied advanced oxidation systems, pollutant degradation followed a pseudo first order kinetics. The degradation pathway of chlorinated and nitro aromatic pollutants includes initial •OH radicals attack to aromatic ring with hydroxylated intermediates formation, followed by their step by step oxidation up to carboxylic acids. Inorganic ions like Cl-, NO3-, NH4+ are also formed as mineralization products.

Collagen production is generating wastewater with high organic loading. This type of wastewater is still containing valuable compounds that can be reused in other applications. In order to investigate the possibility to recover and reuse these compounds the membrane based processes were investigated. Four types of commercial available membranes were characterised and then used to recover the proteins. The results proved that membrane based processes represent a viable alternative to treatment of wastewater generated by collagen production facilities when recovery of valuable compounds is envisaged. It has to be stressed that on the other hand only membrane processes do not assure too reach the quality norms imposed by the legislation for treated wastewater discharge into sewerage systems or natural receivers. Therefore, when proteins recovery and reuse is wanted, the membrane processes represent only the first step of wastewater treatment and should be followed by biological processes in order to obtain the organic loading quality indicators required for wastewater treatment plants discharges.

The influence of attached biomass bioreactor types on the denitrification process using a low-pitched groundwater containing nitrates was studied. Two types of fixed-bed and fluidized-bed biofilm reactors, equipped with expanded clay granular filler, with a particle size fraction of 2-5 mm were used. The nitrite and nitrate concentrations in the inflow and outflow of the two bioreactors were analytically determined. Based on the obtained concentration values, the denitrification rates were calculated, ranging between 1275�1387 g NO3-N/m3/day in the case of the fixed bioreactor and between 3390�3867 g NO3-N/m3/day in the case of the fluidized bed bioreactor.

Ifosfamide (IF) degradation from aqueous system via UV-Vis Fe-TiO2 system was studied for a photo catalyst dose of 200 mg/L and an irradiation time up to 240 min. IF degradation efficiency was monitored via Liquid Chromatography-Mass Spectrometry technique (LC-MS). Experimental photocatalytic tests were performed both in the absence and presence of 2-propanol and F- radicals� scavengers and the results proved that IF degradation occurs most likely in the bulk solution. Experimental results showed that degradation efficiencies for IF varied between 39.52% in the presence of 2-propanol and 70.70% in the scavengers� absence. Six degradation intermediates were identified using the same LC-MS technique and a three stage degradation pathway was proposed based on both available literature data and evolution of degradation intermediates peaks.

The correct treatment of d electrons is of prime importance in order to predict the electronic properties of the prototype chalcopyrite semiconductors. The effect of d states is linked with the anion displacement parameter u, which in turn influences the bandgap of these systems. Semilocal exchange-correlation functionals which yield good structural properties of semiconductors and insulators often fail to predict reasonable u because of the underestimation of the bandgaps arising from the strong interplay between d electrons. In the present study, we show that the meta-generalized gradient approximation (meta-GGA) obtained from the cuspless hydrogen density (MGGAC) [Phys. Rev. B 100, 155140 (2019)] performs in an improved manner in apprehending the key features of the electronic properties of chalcopyrites, and its bandgaps are comparative to that obtained using state-of-art hybrid methods. Moreover, the present assessment also shows the importance of the Pauli kinetic energy enhancement factor, $\alpha=(\tau-\tau^W)/\tau^{unif}$ in describing the d electrons in chalcopyrites. The present study strongly suggests that the MGGAC functional within semilocal approximations can be a better and preferred choice to study the chalcopyrites and other solid-state systems due to its superior performance and significantly low computational cost., Comment: 12 pages, 8 figures

Accurate prediction of water properties in its gas and condensed phases, including the interaction of water with surfaces, is of prime importance for many scientific disciplines. However, accurate simulation of all water properties together within semilocal approximations of the density functional theory possesses great challenges. The Strongly Constrained and Appropriately Normed semilocal density functional, which satisfies 17 known exact constraints and includes the intermediate range van der Waals interaction, performs quite well for different properties of water including the correct energy ordering of isomers. Despite its impressive performance, the energy overestimation for water isomers, ice lattice energies, and volume underestimation for ice are noticeable. However, it is recently shown that [S. Jana et al., J. Chem. Theory Comput. 16(2), 974–987 (2020)] meta-generalized gradient approximations based on the density matrix expansion [i.e., Tao-Mo (TM) and revised TM (revTM)] can achieve quite a good accuracy for the diverse properties of water. In this paper, we assess the performance of the dispersion corrected counterparts of the TM and revTM functionals. It is shown that the dispersion corrected counterparts of both methods are also quite accurate for diverse water properties, especially for the water–solid interactions. Moreover, the extent of accuracy of TM-based functionals is also analyzed from the viewpoint of the density and functional-driven error. Finally, a comparison in the performance of the dispersion corrected functionals is exhibited. It is shown that the “Optimized Power” damping function together with Grimme’s D3 correction and revTM functional is in excellent agreement for the water adsorption on carbon nanostructure materials and ice-lattice mismatch problem without deviating accuracy of other water properties compared to its bare functional.

Photocatalytic degradation of carbamazepine (CBZ) from spiked aqueous solutions, via a UV/TiO2 system, was investigated, and the optimum photocatalyst type (P25 Degussa) and dose (500 mg/L), as well as irradiation time (45 min), were established. The degradation process kinetics was studied, and a degradation rate constant of 3.14 × 10−5 M min−1 was calculated for CBZ, using the Langmuir–Hinshelwood equation. Experiments performed in the presence of scavengers showed that the main reactive species involved in the degradation process are holes and free hydroxyl radicals; superoxide radicals also play a role in CBZ degradation. Eight transformation products of CBZ were identified, and a possible degradation pathway, consisting of four routes, was proposed. Toxicity and genotoxicity tests were also performed for both untreated and treated CBZ solutions, proving that the use of a UV/TiO2 system represents a suitable treatment approach for aqueous systems with CBZ content.

The article highlights the influence of poultry feather flour percentage and compatibilizers on the dielectric properties of composite materials based on low density polyethylene matrix. The behavior of composite materials was determined in terms of dielectric properties and the distribution of poultry feather flour in the basic polymer matrix, to optimize the technology and structure. The results showed that the addition of feather flour in thermoplastic matrix led to an increase in dielectric constant and dielectric loss and the presence of additives leads to better dispersion and processability of the composite material, an observation supported by X-ray analysis.

Semilocal exchange functionals are propitious in describing several properties of solids due to computational competence. For calculating band gaps of solids, the underestimation of generalized gradient approximation (GGA) functionals is known. The next rung of GGA in Jacob's ladder, i.e., meta-GGA, is expected to improve the band-gap calculation. In this regard, exchange-only potentials are very effective in producing accurate band gaps of solids. But, due to the presence of lattice-dependent parameters, these methods are incompetent for monolayers or slabs. Here, we show the potency of advance meta-GGA energy functionals in elucidating the band gaps of different layered structures. The recently proposed MGGAC meta-GGA functional by Patra et al. Phys. Rev. B 100, 155140 (2019) has proved to be very promising for band gaps within the semilocal treatment of density-functional theory. This conclusion is acquired by applying these functionals to encouraging examples of doped graphene, graphane, and halogenated graphene having insulating band gaps. Also, the improved values of energies of hydrogen-terminated Si(111) surface states are demonstrated with this meta-GGA functional.

We assess several recently developed dispersion-corrected exchange-correlation functionals [PBE + VV10L of H. Peng and J. P. Perdew, Phys. Rev. B 95, 081105 (2017); SG4 + VV10m of A. V. Terentjev et al., Computation 6, 7 (2018); and PBEsol+VV10s of A. V. Terentjev et al., Phys. Rev. B 98, 214108 (2018)] for the adsorption of a noble-gas atom/monolayer as well as a graphene on the Cu(111), Pt(111), Pd(111), and Ag(111) close-packed surfaces. Most of these systems are characterized by weak interactions between the surface and the atom/monolayer, where the van der Waals interaction dominates. Here we investigate the above mentioned dispersion-corrected exchange-correlation functionals using atomic orbitals instead of plane waves applied in earlier works. We find that PBEsol+VV10s is an optimal functional for such hybrid interfaces, being accurate for both the equilibrium distance and the adsorption energy and providing realistic potential-energy curves. Moreover, we also show that PBEsol+VV10s and SG4+VV10m are both very accurate for the investigation of surface formation energies of all transition metals under consideration, A.V.T. acknowledges Dr. Federico Marchesin for fruitful discussion. E.A. would like to acknowledge financial support from MINECO-Spain through Plan Nacional Grant No. FIS2015-64886.

Triclosan (TCS) is an antimicrobial agent used for personal care products that cannot be removed by wastewater treatment classical processes. TCS persistence and toxicity is asking for alternative treatment methods such as TiO 2 assisted photocatalyse. Due to the fact that within the literature are presented various pathways for TCS degradation via UV/TiO 2 photocatalysis, some data being contradictory, research work aimed to propose a degradation mechanism supported by as many experimental data. TCS degradation pathways confirmed by experimental results were: addition of hydroxyl radicals at TCS non-phenolic ring, proton extraction by hydroxyl radicals and direct interaction with photo generated electrons.

A semilocal exchange-correlation functional is proposed with the efficient prediction of the solid-state band gap. The underlying construction of the exchange functional is based on the modeling of the exchange hole and constructing the exchange energy functional. Being a meta-generalized gradient approximation (meta-GGA) level functional, it holds the key feature of the derivative discontinuity through the generalized Kohn-Sham (gKS) formalism. We validate our construction by demonstrating the functional performance for solid-state band gaps and comparing it with the other meta-GGA and hybrid functionals. It is shown that for the semiconductors having narrow, and moderate band gaps, as well as for layered materials the present functional performs as accurately as (or comparable to) the expensive hybrid functional, while for wide-band gap solids, it outperforms the hybrid functional. This indicates that the present functional holds promise for the multiscale modeling of materials with a very low computational cost. Also, the underlying construction is practically very useful as it can be easily implemented in any density functional platform that supports the gKS formalism.

Long-range-corrected range-separated hybrid approximations of the exchange-correlation (XC) energy are proposed through the satisfaction of the local-density linear response, which requires the second-order term of the XC gradient expansion to vanish. The underlying proposition is tested with the asymptotic Perdew-Burke-Ernzerhof (APBE) [L. A. Constantin et al., Phys. Rev. Lett. 106, 186406 (2011)], PBE constructed for interfaces (PBEint) [E. Fabiano et al., Phys. Rev. B 82, 113104 (2010)], and semiclassical generalized-gradient approximation at fourth order (SG4) [L. A. Constantin et al., Phys. Rev. B 93, 045126 (2016)] functionals by constructing their corresponding exchange holes. Systematic investigation of these long-range-corrected XC hybrids shows improved performance on recovering the local-density linear response. The long-range-corrected XC hybrid based on the APBE functional and satisfying local-density linear response gives promising results compared to the popular LC-$\ensuremath{\omega}\mathrm{PBE}$ for most of the thermodynamical test sets. Most interestingly, the underlying construction and improved performance by these XC hybrids indicate that the proposed methodology can serve as a basis for developing range-separated XC hybrid functionals of greater potentialities in the future, not only long-range-corrected ones but also screened hybrid functionals.

The logarithmic singularity of the Lindhard linear response function plays an important role in various phenomena, such as the long-range Friedel oscillations and Kohn anomaly in phonon dispersion. Such a weak singularity cannot be captured by the known gradient expansion of the kinetic energy (KE), but it can be somewhat mimicked by the second-order gradient singularity expansion (GSE2) developed in this work. We show that the GSE2 Pauli KE potential of atoms, computed with the Kohn-Sham density, is remarkably accurate, being the best possible approximation provided by any second-order KE gradient expansion. Next, we study the utility of GSE2 for orbital-free density functional theory, and we prove that the GSE2-based KE functionals give an important and systematic improvement over other popular KE functionals.

We propose a modified interaction strength interpolation method that is more robust in the quasi-two-dimensional density regime and more accurate than the original method [M. Seidl et al., Phys. Rev. Lett. 84, 5070 (2000)] for the correlation energy and adiabatic integrand of small atoms. This method also allows us to construct correlation energy densities as simple local interpolations along the adiabatic connection. As an example, we develop a generalized gradient approximation correlation functional that performs in line with, and often better than, popular semilocal correlation functionals.

We present the theory of semilocal exchange-correlation (XC) energy functionals which depend on the Kohn–Sham kinetic energy density (KED), including the relevant class of meta-generalized gradient approximation (meta-GGA) functionals. Thanks to the KED ingredient, meta-GGA functionals can satisfy different exact constraints for XC energy and can be made one-electron self-correlation free. This leads to a better accuracy over a wider range of properties with respect to GGAs, often reaching the accuracy of hybrid functionals, but at much reduced computational cost. An extensive survey of the relevant literature on existing KED dependent XC functionals is provided, considering nonempirical, semi-empirical, and fully empirical ones. A deeper analysis and a wide benchmark are presented for functionals derived considering only exact constraints and parameters obtained from model and/or atomic systems.

Nonuniform density scaling in the quasi-two-dimensional (quasi-2D) regime is an important and challenging aspect of the density functional theory. Semilocal exchange-correlation energy functionals, developed by solving the dimensional crossover criterion in the quasi-2D regime, have great theoretical and practical importance. However, the only semilocal generalized gradient approximation (GGA) that has been designed to satisfy this criterion is the Q2D-GGA [L. Chiodo et al., Phys. Rev. Lett. 108, 126402 (2012)]. Here, we establish the applicability, broadness, and accuracy of the Q2D-GGA functional by performing an extensive assessment of this functional for transition metal surface energies. The important characteristic of the surface density localization and oscillation due to the rearrangement of the d electrons is also shown for different metal surfaces.

Due to their quantitative accuracy and ability to solve several difficulties, screened range-separated hybrid exchange-correlation functionals are now a standard approach for ab initio simulation of condensed matter systems. However, the screened range-separated hybrid functionals proposed so far are biased either toward compact or slowly varying densities. In this paper, we propose a screened range-separated hybrid functional, named HSEint, which can well describe these density regimes, achieving good accuracy for both molecular and solid-state systems. The semilocal part of the proposed functional is based on the PBEint generalized gradient approximation [E. Fabiano et al., Phys. Rev. B 82, 113104 (2010)], constructed for hybrid interfaces. To improve the functional performance, we employ exact or nearly exact constraints in the construction of range-separated hybrid functional, such as recovering of the local density linear response and semiclassical atom linear response.

We have developed an exchange-correlation kernel in the framework of time-dependent density-functional theory that remarkably accounts for the electron-hole interaction and the optical properties of semiconductors. This kernel, which we name JGM-G, generalizes the jellium-with-gap kernel of Trevisanutto et al. [Phys. Rev. B 87, 205143 (2013)] by considering the gradient of the density as a new ingredient. We have tested it on various materials, from low-band-gap to wide-band-gap semiconductors, and we have demonstrated that the JGM-G kernel yields an optical response that is close to experiment. These encouraging results indicate that the JGM-G kernel can become a low-cost and practical tool for the description of excitonic effects in semiconductors.

Kinetic energy (KE) approximations are key elements in orbital-free density functional theory. To date, the use of non-local functionals, possibly employing system dependent parameters, has been considered mandatory in order to obtain satisfactory accuracy for different solid-state systems, whereas semilocal approximations are generally regarded as unfit to this aim. Here, we show that instead properly constructed semilocal approximations, the Pauli-Gaussian (PG) KE functionals, especially at the Laplacian-level of theory, can indeed achieve similar accuracy as non-local functionals and can be accurate for both metals and semiconductors, without the need of system-dependent parameters., Comment: 19 pages, 3 figures

Orbital-Free Density Functional Theory (OF-DFT) promises to describe the electronic structure of very large quantum systems, being its computational cost linear with the system size. However, the OF-DFT accuracy strongly depends on the approximation made for the kinetic energy (KE) functional. To date, the most accurate KE functionals are non-local functionals based on the linear-response kernel of the homogeneous electron gas, i.e. the jellium model. Here, we use the linear-response kernel of the jellium-with-gap model, to construct a simple non-local KE functional (named KGAP) which depends on the band gap energy. In the limit of vanishing energy-gap (i.e. in the case of metals), the KGAP is equivalent to the Smargiassi-Madden (SM) functional, which is accurate for metals. For a series of semiconductors (with different energy-gaps), the KGAP performs much better than SM, and results are close to the state-of-the-art functionals with complicated density-dependent kernels., Comment: 11 pages, 4 figure