Density Functional Theory Simulation Results Research Articles

Multiscale Simulations Facilitate the Design of High‐Performance Perovskite Solar Cells

Organic‐inorganic hybrid perovskite solar cells (PSCs) have swiftly emerged as a prominent contender in the photovoltaic industry, owing to their unparalleled optoelectronic capabilities. Nevertheless, the commercial viability of organic‐inorganic hybrid PSCs is significantly hindered by their limited hygrothermal stability. Therefore, based on multiscale simulation technology, we systematically investigated the microscopic properties of CsPbBrxI3−x (0 ≤ x ≤ 3) perovskite materials and the corresponding photovoltaic device performance. Multiscale simulation technology is numerical simulation method that combines the density functional theory (DFT) with finite element method (FEM). DFT is used first to study the energy band structure, density of states, and optoelectronic parameters of CsPbBrxI3−x (0 ≤ x ≤ 3). Then, FEM is used to study the optical properties of all‐inorganic PSCs based on the results of DFT simulation. Finally, the bulk defect concentration (Nt) of the perovskite material, and the defect concentration between the perovskite and the charge transport layer (CTL) on the photovoltaic performance of the device are calculated and analyzed using CsPbI3 PSCs as an example. We finally designed the CsPbI3 all‐inorganic PSCs with a theoretical efficiency of 22.65%. Our theoretical simulation methods and corresponding results present a groundbreaking approach to crafting highly efficient and exceptionally stable all‐inorganic PSCs.

Exploring the carbon-chain structure-activity relationship of CO2 and ketone-based absorbents

With regard to the physical absorbents for CO2 removal, the alteration of carbon-chain structure may benefit the CO2 absorption performance. However, the relationship between the carbon-chain structure of ketones absorbents and their CO2 absorption capacity has rarely been studied, and the related mechanism is unclear. In this study, theoretical calculations and thermodynamic experiments were carried out to explore the effects of the carbon-chain length and isomerism of ketones on their CO2 absorption performance. The density functional theory (DFT) simulations show that the F-∥ configuration is more stable than the others for the CO2+ketone complex in most cases. The followings are obtained according to the experimental results, which are pretty consistent with DFT calculations. The dissolution of CO2 in the ketone is a typical physical process. As the number of carbon atom increases, the CO2 absorption capacity of straight-chain ketones increases. Straight-chain ketones exhibit higher CO2 absorption capacity than branched-chain ones. The effect of increasing carbon-chain length and isomerism on CO2 absorption capacity are both stronger for the ketones with fewer carbon atoms; the influence mechanism can be attributed to different degrees of weak hydrogen-bond interaction between CO2 and ketone molecules, suggested by the DFT simulation results. The above conclusions are beneficial for the development of potential CO2 capture absorbents. In addition, the industrial application feasibility of surveyed ketone absorbents is also discussed.

Investigation on removal of multi-component volatile organic compounds in a two-stage plasma catalytic oxidation system - Comparison of X (X=Cu, Fe, Ce and La) doped Mn2O3 catalysts

Mn2O3-X catalysts (X = Cu, Fe, Ce and La) were prepared based on γ-Al2O3 for the mixture degradation of muti-component volatile organic compounds (VOCs) composed of toluene, acetone, and ethyl acetate. The catalysts were characterized, and the density functional theory (DFT) simulation of ozone adsorption on Mn2O3-X were carried out to investigate the influence of adsorption energy on catalytic performance. The results showed that the removal efficiency (RE) of each VOC component was similarly improved by Mn2O3-X catalysts, and the greatest increase in VOCs' removal efficiency was obtained (7.8% for toluene, 86.2% for acetone, and 82.5% for ethyl acetate) at a special input energy (SIE) of 700 J L−1 with Mn2O3–La catalyst. Characterization results demonstrated that Mn2O3–La catalyst had the highest content of low valence Mn elements and the greatest Oads/Olatt ratio, as well as the lowest reduction temperature. Mn2O3–La catalyst also presented superior catalytic effect in improving carbon balance (CB) and CO2 selectivity (SCO2). The CB and SCO2 were increased by 47.7% and 12.61% respectively with Mn2O3–La at a SIE of 400 J L−1 compared with that when only γ-Al2O3 was applied. The DFT simulation results of ozone adsorption on Mn2O3-X catalysts indicated that the adsorption energy of catalyst crystal was related to the catalytic performance of the catalyst. The Mn2O3–La/γ-Al2O3 catalyst, which had the highest absolute value of adsorption energy, presented the best performance in improving VOCs’ RE.

Improved flotation of chalcopyrite from galena and pyrite by employing Cu-affinity phosphate collector

Sulfide minerals have similar flotation behavior using the commonly-used collectors such as xanthate due to its low selectivity to active metal ions on sulfide minerals, which leads to difficulties separating chalcopyrite from galena and pyrite. In this work, dibutyl phosphonate (HDBP) was investigated as a collector for chalcopyrite. Flotation tests confirmed that HDBP can selectively and effectively collect chalcopyrite at low concentrations and at environment-friendly pH. This was supported by the results of X-ray photoelectron spectrometry (XPS), electrochemical tests and Density Functional Theory (DFT) simulations. It can be inferred from the XPS results that single-bonded and double-bonded oxygen atoms in the HDBP structure undergo chemisorption with Cu atoms on the surface of chalcopyrite, while HDBP barely interacts with galena and pyrite. This was supported by the results of DFT simulations which showed that the stable adsorption of HDBP on the surface of chalcopyrite is formed by the four-member chelation ring with the P–O–Cu and P=O–Cu bonds with a higher adsorption energy of −133.01 kcal/mol. Electrochemical tests suggested that the corrosion potential and current of the chalcopyrite electrode increase significantly after using HDBP due to the formation of the new oxides. However, for galena and pyrite, there were no obvious changes, which further indicated that HDBP has a strong and selective reactivity to chalcopyrite. The strong affinity of HDBP for Cu atoms means that it has strong potential as a collector for the selective separation of copper-bearing minerals.

Preparation of TiO2/WO3-corn straw based graphene-like composite and its low light catalytic hydrogen production performance and mechanism

In this paper, TiO2/WO3 corn straw graphene-like photocatalyst composite suitable for low light catalytic hydrogen production is prepared by one pot thermal synthesis method. The morphology and structural characteristics of TiO2/WO3 corn straw graphene-like compounds are analyzed. Based on the photoelectric characteristics and density functional theory simulation results, the energy band of TiO2/WO3 corn straw graphene-like composite material is reduced to 2.32 eV compared with pure TiO2 and WO3. The transfer rate of photogenerated carriers is accelerated, and the p-n heterostructure between TiO2 and WO3 interacts with graphene to promote the transfer of photogenerated electrons. Moreover, some photogenerated electrons reside on the graphene surface. Consequently, under low light irradiation, the efficiency of photogenerated electron transfer is increased and the hydrogen production performance is improved. The photocatalytic experiment showed that the hydrogen production rate of TiO2/WO3 corn straw graphene-like composite under low light irradiation is only 10% lower than that under visible light irradiation. Furthermore, the addition of graphene increases the specific surface area of the composite photocatalyst, which makes the composite material more adaptable to low light and improves its feasibility for industrial mass production.

Simulation and experimental study on mechanism and kinetics of 1,1,2-trichloroethane dehydrochlorination reaction

Dehydrochlorination of 1,1,2-trichloroethane (112TCE) is a widely used method for preparing vinylidene chloride (VDC), which is an important polymeric monomer and intermediate of refrigerant. However, there are few reports on kinetics of this reaction system. In this work, density functional theory (DFT) calculation analyses and experiments were conducted to investigate the reaction mechanism and kinetics of 112TCE dehydrochlorination with sodium hydroxide (NaOH). DFT simulation results unveiled there were three parallel reactions which produce VDC, cis-1,2-dichloroethylene (C12DE) and trans-1,2-dichloroethylene (T12DE) respectively in the reaction process of 112TCE and NaOH. The activation energy of the reaction to produce VDC was lower than those of the other two reactions. Moreover, the kinetic parameters of the three parallel reactions, such as reaction orders, rate constants, pre-exponential factors and activation energies, were experimentally obtained by decoupling the overall reaction kinetics. All the parallel reactions are bimolecular elimination reactions and the rate expression of the intrinsic kinetics for generating VDC isdCtdt=1.668×1011e-75662RTCACB. The reaction rate is three orders of magnitude higher than those of producing C12DE and T12DE, which is consistent with the DFT simulation results. These kinetics results are useful for the process optimization and reactor design in VDC production process.

Density Functional Theory Investigation on the Molecular Structure and Vibrational Spectra of Triclosan

Density functional theory (DFT) methods possess a strong ability in the molecular modeling of geometrical and spectroscopic parameters because of their high accuracy and consistency with experimental data. In this study, the performances of different DFT methods to predict the molecular structural and vibrational properties of triclosan were investigated and compared. DFT methods comprised of five commonly used functionals, namely B3LYP, LSDA, PBEPBE, CAM-B3LYP, and M06-2X, were examined. The proper choice of the basis set had a significant influence on the DFT simulation results. Therefore, the effects of different basis sets, including LANL2DZ, SDD, LANL2MB, 6-311G, and 6-311++G(d,p), on the theoretical calculations of triclosan, were also evaluated. Results revealed that the M06-2X/6-311++G(d,p) level of theory was superior to other levels in simulating the structure of triclosan. The LSDA/6-311G level of theory showed the best performance in predicting the vibrational spectra of triclosan. These results can provide a fundamental benchmark for the study of environmental pollution mechanisms and ecological effects of triclosan.

Sulfadiazine degradation by combination of hydrodynamic cavitation and Fenton-persulfate: parametric optimization and deduction of chemical mechanism.

This paper reports the degradation of the sulfadiazine (SDZ) drug with a hybrid advanced oxidation process (AOP) of heterogeneous α-Fe2O3/persulfate coupled with hydrodynamic cavitation. The major objectives of the study are parametric optimization of the process and elucidation of the chemical mechanism of degradation. The optimum conditions for maximum SDZ degradation of 93.07 ± 1.67% were as follows: initial SDZ concentration = 20ppm, pH = 4, α-Fe2O3 = 181.82mg/L, Na2S2O8 = 348.49mg/L, H2O2 = 0.95mL/L, inlet pressure = 0.81MPa (8atm), orifice plate configuration: hole dia. = 2mm and number of holes = 4. Density functional theory (DFT) calculations revealed that the atoms of SDZ with a high Fukui index (f 0) were potentially active sites for the attack of •OH and [Formula: see text] radicals. Fukui index calculation revealed that atom 11N has a higher value of f 0 (0.1026) for oxidation at the α-amine group of the sulfadiazine molecule. Degradation intermediates detected through LC-MS/MS analysis corroborated the results of DFT simulations. Using these results, a chemical pathway has been proposed for SDZ degradation.

Adsorption of hydrated Al3+ on the kaolinite (001) surface: A density functional theory study

In order to reveal the microscopic occurrence of Al3+ impurity in ionic rare earth ore on kaolinite surface, density functional theory (DFT) was used to construct the stable hydrate model of Al3+ in the water system. The structure and bonding mechanism of the complexes of outer layer adsorption and inner layer (monodentate/bidentate) adsorption of hydrate Al3+ on kaolinite (001) surface were studied. The DFT simulation results were verified by molecular dynamics (MD) stimulation and adsorption experiments. The results showed that the stable hydrate form of Al3+ is [Al(H2O)6]3+. When hydrated Al3+ is adsorbed on the outer layer of the kaolinite (001) surface, Al3+ is more inclined to be adsorbed on the SiO surface. When hydrated Al3+ is adsorbed on the inner layer of the kaolinite (001) surface, Al tends to form a bond with Ou atoms formed by the deprotonation of the “upright” hydroxyl group on the surface to form monodentate adsorption complexes, and maintains coordination with the surrounding 5 H2O; Al tends to form bonds with the Ou and Ol atoms formed by the deprotonation of the “upright” and “lying” hydroxyl groups on the surface to form bidentate adsorption complexes, due to steric hindrance effect, Al only maintains coordination with the surrounding 3 H2O. The MD simulation results verified the rationality of the adsorption configuration calculated by DFT. Combined with Mulliken population, charge density and partial density of state (PDOS) analysis, it is shown that the AlOs bond in the monodentate/bidentate adsorption complex of hydrated Al3+ has the characteristics of strong ionicity and strong bond filling. The hydrated Al3+ preferentially forms a more stable bidentate adsorption complex on kaolinite surface. Both the calculation of adsorption energy and the results of adsorption experiments support this conclusion.

Experimental and theoretical studies of chitosan dissolution in ionic liquids: Contribution ratio effect of cations and anions

Typical hydrogen bonding information (hydrogen bonds, hydrogen bond lengths, and average bond lengths) and weak interaction energy (ΔH) of four ionic liquids (ILs), anion/chitobiose, cation/chitobiose, and IL/chitobiose complexes were determined using density functional theory (DFT) calculations to elucidate the contribution ratio effect of ions (cations or anions of ILs) upon chitosan dissolution.For [Emim]Ac and [Bmim]Ac with same acetate anion, contribution ratio (Rc) values of cations in [Bmim]Ac and [Emim]Ac increased from 37.88% to 38.14%. For [Bmim]Cl and [Etmim]Cl with same chloride anion, contribution ratio (Rc) values of cations increased slightly from 39.39% to 41.65%. As for [Bmim]Cl and [Bmim]Ac with same cation, contribution ratio (Rc) values of Cl- anion in [Bmim]Cl (60.61%) was lower than that of acetate anion in [Bmim]Ac (62.12%).These changes revealed that cations of ILs played more important role in chitosan dissolution.Hydrogen-bond basicity values (β values) of ILs were closely related to the DFT simulation results (weak interaction energy and average hydrogen bond length values) of ILs. Chitosan dissolved faster in acetate based imidazolium ILs ([Emim]Ac and [Bmim]Ac) than the chloride based ILs ([Bmim]Cl and [Etmim]Cl). The chitosan dissolution performance in ILs was consistent with DFT simulation results (weak interaction energy values and average hydrogen bond length values) of IL/chitobiose and hydrogen-bond basicity values of ILs.

In situ NMR Investigation of the Photoresponse of Perovskite Crystal

Summary Hybrid perovskites are outstanding candidates for use in optoelectronic devices. Nonetheless, hybrid perovskites present numerous fundamental issues that are not yet fully understood. This study seeks to address this problem by reporting on the occurrence of ultraslow dynamic orientation changes in the methylammonium (MA) cations and the corresponding changes in the inorganic lattice of MAPbI3 perovskite crystals occurring over a time scale of 100 s under continuous illumination based on in situ single-crystal 2H nuclear magnetic resonance and in situ X-ray diffraction results. The demonstrated ultraslow dynamic changes in MAPbI3 are far slower than elementary molecular motions typically having time scales of femtoseconds and picoseconds and have never been reported previously. The ultraslow dynamic changes have been correlated with the reduction of band gap and the increase of absorption coefficient of MAPbI3, providing the molecular origins of the stabilization process in the photoresponse of the MAPbI3 device.

Theoretical and experimental studies of ionic liquid-urea mixtures on chitosan dissolution: Effect of cationic structure

Two imidazolium chloride ionic liquids (ILs) were mixed with urea for chitosan dissolution. Ionic liquids were [Amim]Cl and [Etmim]Cl (1-allyl-3-methyl-imidazolium chloride and 3-methyl-1-(ethylacetyl)imidazolium chloride, respectively). Physicochemical properties of neat ILs and IL-Urea solutions (including density, viscosity, conductivity, β value, π* value, and thermogravimetric analysis), were thoroughly investigated. Dissolution performance of chitosan in IL-Urea solutions was determined.Chitobiose (KET) as model chitosan structure, density functional theory (DFT) calculations were used to discuss the interactions between IL, urea, and chitobiose, and to clarify the different physicochemical properties of ILs, IL-Urea solutions. Also DFT simulation results were used for elucidating the influence of different cationic substituents and urea addition for chitosan dissolution.[Etmim]Cl showed higher density, viscosity, conductivity, β, and π* value than those of [Amim]Cl. These results revealed strong hydrogen bonds among [Etmim]Cl owing to the carboxylic acid ester group than allyl group of [Amim]Cl. Densities, viscosities, and π* values of IL-Urea solutions increased with increasing urea content. Conductivities and β values of IL-Urea solutions decreased with the increase of urea content at same temperature. The thermal stability of [Amim]Cl-Urea mixture increased when urea content increased from 10% to 30%, which was different from [Bmim]Cl-Urea melt. The thermal stability of [Etmim]Cl-Urea mixture was different to that of [Amim]Cl-Urea mixture.Urea was accommodated in ILs, forming hydrogen bonds with both the anion and cation in ILs, which changed the molecular interactions of ILs. The influence of different substituents in imidazolium ILs and urea addition on chitosan dissolution were analyzed using experimental determination and DFT calculations. Cationic substituents of imidazolium ILs play an extraordinary role in hydrogen bonds formation with chitobiose, so to strengthen chitosan dissolution. The information obtained would provide a guide for designing novel IL solvent systems for chitosan dissolution.

Zirconocene-Catalyzed Dimerization of α-Olefins: DFT Modeling of the Zr-Al Binuclear Reaction Mechanism.

Zirconocene-mediated selective dimerization of α-olefins usually occurs when precatalyst (η5-C5H5)2ZrCl2 is activated by minimal excess of methylalumoxane (MAO). In this paper, we present the results of density functional theory (DFT) simulation of the initiation, propagation, and termination stages of dimerization and oligomerization of propylene within the framework of Zr-Al binuclear mechanism at M-06x/DGDZVP level of theory. The results of the analysis of the reaction profiles allow to explain experimental facts such as oligomerization of α-olefins at high MAO/(η5-C5H5)2ZrCl2 ratios and increase of the selectivity of dimerization in the presence of R2AlCl. The results of DFT simulations confirm the crucial role of the presence of chloride in the selectivity of dimerization. The molecular hydrogen was found in silico and proven experimentally as an effective agent that increases the rate and selectivity of dimerization.

Cu Diffusion in Amorphous Ta2O5 Studied with a Simplified Neural Network Potential

Understanding atomistic details of diffusion processes in amorphous structures is becoming increasingly important due to the recent advances in various information and energy devices. Atomistic simulations based on the density functional theory (DFT) represent a powerful approach; however, the development of a method characterized by both high reliability and computational efficiency remains a challenge. In this study, a simple neural network (NN) interatomic potential is constructed from the results of DFT simulations to investigate the diffusion of a single Cu atom in amorphous Ta2O5. The proposed technique is as accurate as the DFT in predicting hopping paths and the corresponding barrier energies in a given amorphous structure. Although the developed NN-based approach exhibited some limitations since it was constructed specifically for Cu, the obtained results showed that the NN potential was able to satisfactorily describe the Cu diffusion behavior. Thus, the Cu diffusion activation energy calculated...

Systematic study of electronic structure and band alignment of monolayer transition metal dichalcogenides in Van der Waals heterostructures

Two-dimensional transition metal dichalcogenides (TMDs) are promising low-dimensional materials which can produce diverse electronic properties and band alignment in van der Waals heterostructures. Systematic density functional theory (DFT) calculations are performed for 24 different TMD monolayers and their bilayer heterostacks. DFT calculations show that monolayer TMDs can behave as semiconducting, metallic or semimetallic depending on their structures; we also calculated the band alignment of the TMDs to predict their alignment in van der Waals heterostacks. We have applied the charge equilibration model (CEM) to obtain a quantitative formula predicting the highest occupied state of any type of bilayer TMD heterostacks (552 pairs for 24 TMDs). The CEM predicted values agree quite well with the selected DFT simulation results. The quantitative prediction of the band alignment in the TMD heterostructures can provide an insightful guidance to the development of TMD-based devices.

Visible-Light-Responsive Graphitic Carbon Nitride: Rational Design and Photocatalytic Applications for Water Treatment.

Graphitic carbon nitride (g-C3N4) has recently emerged as a promising visible-light-responsive polymeric photocatalyst; however, a molecular-level understanding of material properties and its application for water purification were underexplored. In this study, we rationally designed nonmetal doped, supramolecule-based g-C3N4 with improved surface area and charge separation. Density functional theory (DFT) simulations indicated that carbon-doped g-C3N4 showed a thermodynamically stable structure, promoted charge separation, and had suitable energy levels of conduction and valence bands for photocatalytic oxidation compared to phosphorus-doped g-C3N4. The optimized carbon-doped, supramolecule-based g-C3N4 showed a reaction rate enhancement of 2.3-10.5-fold for the degradation of phenol and persistent organic micropollutants compared to that of conventional, melamine-based g-C3N4 in a model buffer system under the irradiation of simulated visible sunlight. Carbon-doping but not phosphorus-doping improved reactivity for contaminant degradation in agreement with DFT simulation results. Selective contaminant degradation was observed on g-C3N4, likely due to differences in reactive oxygen species production and/or contaminant-photocatalyst interfacial interactions on different g-C3N4 samples. Moreover, g-C3N4 is a robust photocatalyst for contaminant degradation in raw natural water and (partially) treated water and wastewater. In summary, DFT simulations are a viable tool to predict photocatalyst properties and oxidation performance for contaminant removal, and they guide the rational design, fabrication, and implementation of visible-light-responsive g-C3N4 for efficient, robust, and sustainable water treatment.

ADSORPTION OF NANOWOLLASTONITE ON CELLULOSE SURFACE: EFFECTS ON PHYSICAL AND MECHANICAL PROPERTIES OF MEDIUM-DENSITY FIBERBOARD (MDF)

ABSTRACT Effects of nanowollastonite (NW) adsorption on cellulose surface were studied on physical and mechanical properties of medium-density fiberboard (MDF) panels; properties were then compared with those of MDF panels without NW-content. The size range of NW was 30-110 nm. The interaction between NW and cellulose was investigated using density functional theory (DFT). Physical and mechanical tests were carried out in accordance with the Iranian National Standard ISIRI 9044 PB Type P2 (compatible with ASTM D1037-99) specifications. Results of DFT simulations showed strong adsorption of NW on cellulose surface. Moreover, mechanical properties demonstrated significant improvement. The improvement was attributed to the strong adsorption of NW on cellulose surface predicted by DFT, adding to the strength and integrity between wood fibers in NW-MDF panels. It was concluded that NW would improve mechanical properties in MDF panels as a wood-composite material, as well as being effective in improving its biological and thermal conductivity.

Spectroscopic Investigation of Plasma-Fluorinated Monolayer Graphene and Application for Gas Sensing.

Large-area monolayer fluorinated graphene (FG) is synthesized by a controllable SF6 plasma treatment. The functional groups of FG are elucidated by various spectroscopies, including Raman spectroscopy, X-ray photoemission spectroscopy (XPS), and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Raman results suggest that the defects are introduced into the monolayer graphene during the fluorination process. The fluorine content can be varied by the plasma treatment and can reach the maximum (∼24.6 atom % F) under 20 s of plasma treatment as examined by XPS measurement. The angle-dependent NEXAFS results reveal that the fluorine atoms interact with the graphene matrix to form covalent C-F bonds, which are perpendicular to the basal plane of FG. FG is applied as a gas-sensing material and owns much better performance for ammonia detection compared to pristine graphene. On the basis of our density functional theory simulation results, the fast response/recovery behavior and high sensitivity of the FG gas sensor are attributed to enhanced physical absorption due to the C-F covalent bonds on the surface of FG.

DFT theoretical and FT-IR spectroscopic investigations of the plasticity of clay minerals dispersions

Plasticity is the most important property of dispersions of clay minerals that determine the character of participation of these systems in many natural and technological processes. We report on the results of studies of hydration mechanism in typical clay minerals making part of natural dispersions of sedimentation masses by means of IR spectroscopy and theoretical density functional theory (DFT) methods. X-ray diffraction analysis of clay minerals of Millerovo mineral deposit (Russian Federation) is carried out. Regularities and peculiarities of interaction of water molecules with kaolinite basal planes (001) and (001¯) are analyzed. The role of water in the formation of plasticity of clay minerals dispersions is revealed. The modes of water molecules placement and their state and structure in the system “clay mineral-water” is defined. Phase transition processes of clay minerals dispersion into plastic and liquid state and their influence on spectral characteristics of the systems are investigated. The interpretation of clay minerals phase transitions into plastic and fluid state based on the results of DFT simulation is given. The relation is established between specific variation of spectral characteristics and phase transitions of clay minerals dispersions into plastic and liquid state.

Experimental study of strontium adsorption on anatase nanoparticles as a function of size with a density functional theory and CD model interpretation.

The effect of particle size on the adsorption of Sr(2+) onto monodisperse nanometer diameter (4, 20, and 40 nm) anatase samples has been evaluated quantitatively with macroscopic experimental studies. The adsorption of Sr(2+) onto the anatase particles was evaluated by potentiometric titrations in NaCl media, at two ionic strengths (0.03 and 0.3 m), and over a wide range of pH (3-11) and surface loadings, at a temperature of 25 °C. Adsorption of Sr(2+) to the surface of the 20 and 40 nm diameter samples was similar, whereas the Sr(2+) adsorption titration curves were shallower for the 4 nm diameter samples. At high pH, the smallest particles adsorbed slightly less Sr(2+) than was adsorbed by the larger particles. At the molecular scale, density functional theory (DFT) calculations were used to evaluate the most stable Sr(2+) surface species on the (101) anatase surface (the predominant crystal face). An inner-sphere Sr-tridentate surface species was found to be the most stable. The experimental data were described with a charge distribution (CD) and multisite complexation (MUSIC) model, with a Basic Stern layer description of the electric double layer. The resulting surface complexation model explicitly incorporated the molecular-scale information from the DFT simulation results. For 20 and 40 nm diameter anatase, the CD value for the Sr-tridentate species was calculated using a bond valence interpretation of the DFT-optimized geometry. The CD value for the 4 nm sample was smaller than that for the 20 and 40 nm samples, reflecting the shallower Sr(2+) adsorption titration curves. The adsorption differences between the smallest and larger anatase particles can be rationalized by water being more highly structured near the 4 nm anatase sample and/or the Sr-tridentate surface species may require more well-developed surface terraces than are present on the 4 nm particles.