SCF Method Research Articles

Characterization of peroxide on coal surface: A combined △SCF and XPS study

X‐ray photoelectron spectroscopy (XPS) is widely used to determine the composition of elements and oxygen‐containing functional groups. Accurate determination of core‐electron binding energies (CEBEs) is essential for identifying the types and contents of oxygen‐functional groups present on the surface of coal. The △SCF method has been carried out on CEBEs for an extensive series of oxygen‐containing organic systems encompassing the most common functionalities. The polymers for which experimental values are available for comparison demonstrate the adequacy of the treatment for describing CEBEs for the O1s core level. Therefore, a sound basis is provided for the discussion of CEBEs (O1s) for functionalities for which experimental values are not accurate or available, such as carbonyl, carboxyl, and peroxide. The results are applied to the XPS study of oxidized coal. The change law of peroxide and oxygen‐containing functional groups was discussed. The calculation method and results in this paper can provide a guide for readers to use XPS to study the oxidation of coal surfaces.

Multiconfigurational SCF and Short-Range DFT Combined with Polarizable Density Embedding: Comparison of Linear-Response and State-Specific Solvatochromic Shifts of Acrolein and Para-nitrophenolate in Water.

The polarizable density embedding model is combined with the multiconfigurational self-consistent field and MC-srDFT electronic structure methods to calculate solvatochromic shifts of the n-π* absorption of acrolein and the π-π* absorption of the para-nitrophenolate anion in aqueous solution. Differences between linear-response (LR) and state-specific (SS) solvent shifts are analyzed by assessing the contributions of different terms in the solvent potential. This comparison shows that the differences are not only due to the intrinsically different response of LR and SS excitation energies to the polarizability of the environment but also due to a different response to the static part of the environment potential. These observations show that even in nonpolarizable environments, LR and SS calculations based on SCF (orbital optimization) methods do not necessarily agree on the spectral shift. The difference can be as large as, or even dominate, the difference due to dynamical polarization.

Stress influence matrix on hot spot stress analysis for welded tubular joint in offshore jacket structure

The detailed finite element (DFE) simulation of welded offshore tubular joint can give realistic and sound hot-spot stress (HSS) estimates regarding fatigue design of jacket substructures for offshore wind turbines. However, the computational efforts and time costs due to complicated joint configurations and a large quantity of design load cases have prompted the design practitioners likely resort to a simple alternative, the SCF method, which is also rooted in the DFE simulation. The present study attempted to optimize the conventional DFE simulation procedure by applying a stress influence matrix (SIM) method and its modified version gSIM, along with discrete joint formulation techniques, to simplify and make efficient of the DFE process, and then incorporating point positioning techniques to eventually ease the HSS evaluation. Through an implementation case involving a KK tubular joint, the gSIM method proved its robustness, reliability and computationally efficiency in joint HSS evaluation practice.

Квантово-химическое исследование потенциалов взаимодействия молекул CF-=SUB=-4-=/SUB=-, CH-=SUB=-4-=/SUB=-, SiF-=SUB=-4-=/SUB=- и SiH-=SUB=-4-=/SUB=- с атомом Rb в основном и электронно-возбужденных состояниях

The potentials of the electronic states of RbXY4 molecules, XY4 = CF4, CH4, SiF4 and SiH4, correlating with the ground 5s 2S1/2 and excited 5p 2P1/2, 3/2 states of the Rb atom are studied using the methods of ab initio quantum chemistry. The calculations are performed by the SCF method of the full active space of orbitals, taking into account dynamic electronic correlations and spin-orbital interaction. It is established that the character of the interaction in the A and A' states, correlating respectively with the lower and upper states of the Rb 5p 2P1/2, 3/2 doublet and corresponding to the perpendicular orientation of the Rb p-orbital relative to the Rb–X axis, differ significantly (attraction or repulsion) for different XY4 molecules, which is explained by the difference in the charge distribution in the XY4 molecules. In order to evaluate the accuracy of the calculation results for RbXY4 molecules, similar calculations are performed for the diatomic RbAr molecule using different basis sets. It is found that, as compared with the A and A' states, the potential of the repulsive B state, which correlates with the upper state of the doublet and corresponds to the orientation of the Rb p-orbital along the Rb–X axis, is significantly more sensitive to the size of the basis set which is due to the accuracy of accounting for the configuration interaction with states that correlate with the Rb(6s 2S1/2) and Rb(4d 2D3/2, 5/2) states and other states of the Rb atom lying above Rb(5p 2P1/2, 3/2).

Ab Initio Study of the Interaction Potentials of CF-=SUB=-4-=/SUB=-, CH-=SUB=-4-=/SUB=-, SiF-=SUB=-4-=/SUB=- and SiH-=SUB=-4-=/SUB=- Molecules with the Rb Atom in the Ground and Electronically Excited States

The potentials of the electronic states of RbXY4 molecules, XY4 = CF4, CH4, SiF4 and SiH4, correlating with the ground 5s 2S1/2 and excited 5p ^2P1/2,3/2 states of the Rb atom are studied using the methods of ab initio quantum chemistry. The calculations are performed by the SCF method of the full active space of orbitals, taking into account dynamic electronic correlations and spin-orbital interaction. It is established that the character of the interaction in the A and A' states, correlating respectively with the lower and upper states of the Rb (5p ^2P1/2,3/2) doublet and corresponding to the perpendicular orientation of the Rb p-orbital relative to the Rb-X axis, differ significantly (attraction or repulsion) for different XY4 molecules, which is explained by the difference in the charge distribution in the XY4 molecules. In order to evaluate the accuracy of the calculation results for RbXY4 molecules, similar calculations are performed for the diatomic RbAr molecule using different basis sets. It is found that, as compared with the A and A' states, the potential of the repulsive B state, which correlates with the upper state of the doublet and corresponds to the orientation of the Rb p-orbital along the Rb-X axis, is significantly more sensitive to the size of the basis set which is due to the accuracy of accounting for the configuration interaction with states that correlate with the Rb (6s ^2S1/2) and Rb (4d ^2D3/2,5/2) states and other states of the Rb atom lying above Rb (5p ^2P1/2,3/2). Keywords: alkali metals, excited states, carbon tetrafluoride, quantum chemistry, ab initio calculations.

Fracture toughness of 3Y‐TZP ceramic determined by modified SCF method based on femtosecond laser

AbstractIn this work, the femtosecond laser was used to replace the traditional indentation to process ultra‐sharp defects on the test bars for the fracture toughness testing of 3 mol% yttria‐stabilized tetragonal zirconia polycrystals (3Y‐TZP) ceramic materials by a modified SCF method. Finite element (FE) analysis shows that the positions of the maximum stress on the crack tip of the two types of defects are almost the same. Thus, the fracture toughness is calculated based on classical beam deflection theory by comparing their stress intensity factors. Results show that the ratio of the stress intensity factors almost keeps constant when the length and depth of the defects are controlled in a certain range. 3Y‐TZP ceramic material is used as a typical material to study fracture toughness for the verification of this method. The fracture toughness of 3Y‐TZP ceramics determined by this method is 4.4 MPa·m1/2 which coincides with the fracture toughness values tested by traditional SCF method, SEPB method, and SEVNB method. This method exhibits an obvious advantage in good high accuracy and operability for reliable fracture toughness testing of structural ceramics with a smaller defect.

A Simple Effective SCF Method for Computing Optical Gaps in Organic Chromophores

Photoluminescence effects in organic chromophores are of significant importance and requires precise description of low lying excited states. In this communication, we put forward an alternative time-independent DFT scheme for computing lowest single-particle excitation energy, especially for singlet excited state. This adopts a recently developed "virial"-theorem based model of singlet-triplet splitting which requires a DFT calculation on closed shell ground state and a restricted open-shell triplet excited state, followed by a simple integral evaluation. This produces vertical excitation energies in small molecules, linear and non-linear polycyclic aromatic hydrocarbon and organic dyes in comparable accuracy to the TDDFT. We also explore the functional dependency of present method with three different functionals (B3LYP, wB97X and CAM-B3LYP) for polyenes and linear acenes. A systematic comparison with literature value illustrates the validity and usefulness of the present scheme in determining optical gap with fair computational cost.

Second-Order Orbital Optimization with Large Active Spaces Using Adaptive Sampling Configuration Interaction (ASCI) and Its Application to Molecular Geometry Optimization.

Recently, selected configuration interaction (SCI) methods that enable calculations with several tens of active orbitals have been developed. With the SCI subspace embedded in the mean field, molecular orbitals with an accuracy comparable to that of the complete active space self-consistent field method can be obtained. Here, we implement the analytical gradient theory for the single-state adaptive sampling CI (ASCI) SCF method to enable molecular geometry optimization. The resulting analytical gradient is inherently approximate due to the dependence on the sampled determinants, but its accuracy was sufficient for performing geometry optimizations with large active spaces. To obtain the tight convergence needed for accurate analytical gradients, we combine the augmented Hessian (AH) and Werner-Meyer-Knowles (WMK) second-order orbital optimization methods with the ASCI-SCF method. We test these algorithms for orbital and geometry optimizations, demonstrate applications of the geometry optimizations of polyacenes and periacenes, and discuss the geometric dependence of the characteristics of singlet ASCI wave functions.

Development of Components of Prolonged Action Antibacterial Dosage Forms Using SCF Technologies

Gentamicin and levofloxacin are encapsulated into bioresorbable polymer scaffolds and microparticles by the SCF methods: particles from gas saturated solutions (PGSS) and plasticization, with the subsequent foaming of amorphous polymers using supercritical carbon dioxide. The kinetics of the release of the incorporated drug substances into model physiological media are studied. It is shown that the use of the developed methods of SCF-encapsulation of drugs in bioresorbable carriers allows varying the size, shape, and morphology of the formed structures and, accordingly, the rate of release of the drugs into the physiological environments. In our opinion, this approach can be very promising for the development of components of new highly effective antibacterial prolonged action dosage forms.

HOMO-LUMO Energy Levels and the Bandgaps to Understand Porpc Photocatalytic Activity

A dye-sensitized solar cell (DSSC) assembly can be used not only to harvest solar energy but also to purify water using suitable dye-sensitizers. Here, we theoretically investigated four dye-sensitizers, namely, PORPC-1, PORPC-2, PORPC-3, and PORPC-4 for photocatalytic water purification using PBE, B3LYP, PBE0 functionals, and ∆SCF, TD-DFT and GW methods to characterize their activity trends. The energy levels of highest occupied molecular orbitals (HOMO) and the lowest unoccupied molecular orbitals (LUMO) were elucidated using gas-phase and aqueous phase calculations to understand charge injection ability and the dye-regeneration process. However, PBE, B3LYP, PBE0, and TD-DFT methods fail to predict the best sensitizers. The ∆SCF coupled with the implicit solvation method and the GW method HOMO-LUMO energies corrected for aqueous environment effect predicted PORPC-2 and PORPC-4 as the best sensitizers. Thus, it emphasized the importance of aqueous environment effect in simulation. However, none of these methods accurately predicted the photocatalytic performance trend of all the four dye-sensitizers. Hence, we have used the dye-molecular aggregation assembly pattern in an aqueous environment to further probe into activity trends and found that the PORPC-3 and the PORPC-4 prefer J-aggregate assembly, whereas the PROPC-1 and the PORPC-2 adopt H-aggregate assembly pattern. Therefore, the synergistic effect of the HOMO-LUMO energy levels and the aggregate assembly pattern determine the photocatalytic performance of the dye-molecules, and the activity trend is PORPC-4>PORPC-2>PORPC-3>PORPC-1, agreed well with the experimental findings. Acknowledgements This study was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (Nos. NRF-2017R1E1A1A01074266, NRF-2015M1A2A2057129, and NRF-2016M1A2A2937151).

Optimal Orbital Selection for Full Configuration Interaction (OptOrbFCI): Pursuing the Basis Set Limit under a Budget.

Full configuration interaction (FCI) solvers are limited to small basis sets due to their expensive computational costs. An optimal orbital selection for FCI (OptOrbFCI) is proposed to boost the power of existing FCI solvers to pursue the basis set limit under a computational budget. The optimization problem coincides with that of the complete active space SCF method (CASSCF), while OptOrbFCI is algorithmically quite different. OptOrbFCI effectively finds an optimal rotation matrix via solving a constrained optimization problem directly to compress the orbitals of large basis sets to one with a manageable size, conducts FCI calculations only on rotated orbital sets, and produces a variational ground-state energy and its wave function. Coupled with coordinate descent full configuration interaction (CDFCI), we demonstrate the efficiency and accuracy of the method on the carbon dimer and nitrogen dimer under basis sets up to cc-pV5Z. We also benchmark the binding curve of the nitrogen dimer under the cc-pVQZ basis set with 28 selected orbitals, which provide consistently lower ground-state energies than the FCI results under the cc-pVDZ basis set. The dissociation energy in this case is found to be of higher accuracy.

Comparison of fracture toughness testing by the single edge v-notch beam and the surface crack in flexure method on silicon nitride

This work is intended to compare the SEVNB and the SCF methods for fracture toughness testing. Both of the test methods are applied to a silicon nitride. Both methods are standardized and both have some minor shortcomings with respect to practicability and match of the theoretical description of the test situation with the actual test situation. SEVNB is easy to perform, but uses a notch of known depth (+ small micro-cracks of unknown size in front of a notch) instead of a crack, SCF uses a presumably residual stress-free indentation crack which is sometimes difficult to measure, not always semi-elliptical, as assumed to apply the evaluation formula, and may be accompanied by lateral cracks. Both methods will be analysed with respect to possible experimental errors. Variations of the SCF method are applied in order to examine how pre-cracks can be introduced which can be detected on the fracture surface. The geometry of the SCF-pre-crack is varied by applying different loads and by removing different amounts of material. The geometry of the Knoop pre-cracks system is investigated. The results help to identify conditions under which the SCF method can be used successfully to measure the fracture toughness of silicon nitride ceramics.

Preparation, Characterization, and In Vivo Pharmacokinetic Study of the Supercritical Fluid-Processed Liposomal Amphotericin B.

Here, we aimed to prepare and optimize liposomal amphotericin B (AmB) while using the supercritical fluid of carbon dioxide (SCF-CO2) method and investigate the characteristics and pharmacokinetics of the SCF-CO2-processed liposomal AmB. Liposomes containing phospholipids, ascorbic acid (vit C), and cholesterol were prepared by the SCF-CO2 method at an optimized pressure and temperature; conventional liposomes were also prepared using the thin film hydration method and then compared with the SCF-CO2-processed-liposomes. The optimized formulation was evaluated by in vitro hemolysis tests on rat erythrocytes and in vivo pharmacokinetics after intravenous administration to Sprague-Dawley rats and compared with a marketed AmB micellar formulation, Fungizone®, and a liposomal formulation, AmBisome®. The results of the characterization studies demonstrated that the SCF-CO2-processed-liposomes were spherical particles with an average particle size of 137 nm (after homogenization) and drug encapsulation efficiency (EE) was about 90%. After freeze-drying, mean particle size, EE, and zeta potential were not significantly changed. The stability study of the liposomes showed that liposomal AmB that was prepared by the SCF method was stable over time. In vivo pharmacokinetics revealed that the SCF-CO2-processed-liposomes were bioequivalent to AmBisome®; the hemolytic test depicted less hematotoxicity than Fungizone®. Therefore, this method could serve as a potential alternative for preparing liposomal AmB for industrial applications.

Are Inorganic Single-Molecule Magnets a Possibility? A Theoretical Insight into Dysprosium Double-Deckers with Inorganic Ring Systems.

Computational studies of sandwich dysprosium double-decker complexes [Dy(L)2]+/3+ as candidates for single-ion magnets with several inorganic aromatic ring systems (P5-, N5-, B3N3H6, B3P3H6, B3S3H3) have been performed. The molecular structures were optimized with the TPSSh functional, and the ground state properties were investigated with the complete active space SCF method (CASSCF) complemented by the dynamic correlation dressed correction (DCD-CAS(2)) or NEVPT2. Besides the evaluation of the magnetic moment blocking barrier, the impact of the molecular vibration on the relaxation of magnetization was also inspected. We were able to make predictions about the performance of those molecules as single-molecule magnets, where estimated effective energy barrier, Ueff, values are as high as 1475 K in the case of [Dy(N5)2]-, which is the most anisotropic complex from our choice of studied compounds, making them a potentially very effective carbon-free alternative to organometallic double-decker dysprosocenium high-temperature single-molecule magnets.

STUDI POTENSI SENYAWA DERIVATIF FLAVONOID DARI TANAMAN GENUS MACARANGA TERHADAP PROTEIN E6 HPV DENGAN METODE DOCKING MOLECULAR

Interaction study of active compounds of a medicinal plant with cervical cancer cells using the Docking Molecular (In Silico) method. In this research design the active compound sophoraflavanone B, 5,7,3 ', 4'-tetrahidroxy-3,6-diprenylflavone, apigenin and quercetin are first calculated using a quantum approach based on SCF method set 3-21G to obtain a stable compound form and has the lowest energy. Stable compounds interact with cervical cancer cells obtained from protein bank data (GDP) that have been prepared previously to obtain an inhibitory energy value, the number of hydrogen bonds and other factors that influence a Docking Molecular calculation. The interaction of compounds 5,7,3 ', 4'-tetrahydroxy-3,6-diprenylflavone against E6-HPV of 4 hydrogen bonds with a distance of 2.7-3.23 Å.

Coarse‐Grained Dendrimers in a Good Solvent: Comparison of Monte Carlo Simulations, Self‐Consistent Field Theory, and a Hybrid Modeling Strategy

AbstractRecently, a hybrid method has been developed, wherein the positions of some polymer segments are constrained to a small volume. The volume's position is sampled with a Monte Carlo algorithm. The distribution of the remaining segments is determined with Scheutjens–Fleer self‐consistent field theory (SF‐SCF). This incorporates thermal fluctuations into the model. Here it is investigated whether this also leads to an improved treatment of the excluded volume interactions. Dendrimers, with f = 1⋅⋅⋅7 generations, g = 2⋅⋅⋅5 spacers per branch point, and spacers of 20 or 50 segments, are used as a model system. The focus is on the radius of gyration, the asphericity, the radial density, and the end point and first branch point distribution. As expected, both SCF methods underestimate the radius of gyration due to underestimating the short range excluded volume. The SF‐SCF model, however, also gives a slightly different scaling and, in contrast to the other models, also predicts a bimodal distribution for first generation branch points for large f and g. This difference is attributed to overestimating the excluded volume at long ranges. As the hybrid method does not show this, localizing just a few segments largely compensates this shortcoming in the SF‐SCF theory.

Performance of the VBSCF method for pericyclic and π bond shift reactions.

The performance of the valence bond self-consistent field (VBSCF) method was investigated in this paper by predicting the activation barriers and reaction energies in pericyclic and π bond shift reactions for hydrocarbons. The benchmarking set includes 3 electrocyclic reactions, 3 sigmatropic shifts, 3 cycloadditions, 2 cycloreversions, and 7 π bond shift reactions, where the first 11 reactions are taken from Houk's standard set (J. Phys. Chem. A 2003, 107, 11445). Computational results reveal that the VB(CI) method, which performs VBSCF calculations first with full covalent structures and then includes all mono- and di-ionic structures to compute the total energy without further orbital optimization, matches the accuracy of the complete active space SCF (CASSCF) method very well. The mean absolute error values (the deviations from the CASSCF data) are 0.01 kcal/mol for the reaction energy, and 0.26 and 0.32 kcal/mol for the activation energy with the 6-31G and 6-31G(d) basis sets, respectively. © 2018 Wiley Periodicals, Inc.

Fracture toughness testing of biomedical ceramic-based materials using beams, plates and discs

The testing of fracture toughness becomes problematic when only limited amount of material is available that hinders the production of typical beam specimens to be tested in bending. Here we explore fracture toughness testing methodologies that allow for small discs and plates having surface cracks to be tested in biaxial flexure using the Ball-on-3-balls (B3B) set-up, or sawed notches as in the Compact Tension geometry. The B3B-KIc test has shown to be versatile and account for a very small overestimation of the KIc-value in the order of 0.8–1.25% due to in-plane crack mispositioning, and a maximum of 4% if a worst-case scenario of additional out-of-plane mispositioning is assumed. The geometrical factor in the standard SCF method, derived by Newman and Raju, resulted in an overestimation of ∼8% of the KIc-value compared to the new calculation by Strobl et al. for materials with Poisson’s ratio <0.3.

A New Filter Feature Selection Based on Criteria Fusion for Gene Microarray Data

In machine learning and data mining, feature selection aims to seek a compact and discriminant feature subset from the original feature space. It is usually used as a preprocessing step to improve the prediction performance, understandability, scalability, and generalization capability of classifiers. A typical gene microarray data set has the characteristics of high dimensionality, limited samples, and most irrelevant features, and these characteristics make it difficult to discover a compact set of features that really contribute to the response of the model. In this paper, a score-based criteria fusion feature selection method (SCF) is proposed for cancer prediction, and this method aims at improving the prediction performance of the classification model. The SCF method is evaluated on five open gene microarray data sets and three low-dimensional data sets, and it shows superior performance over many well-known feature selection methods when employing two classifiers SVM and KNN to measure the quality of selected features. Experiments verify that SCF is able to find more discriminative features than the competing methods and can be used as a preprocessing algorithm to combine with other methods effectively.

Accelerating Realtime TDDFT with Block-Orthogonalized Manby-Miller Embedding Theory.

Realtime time-dependent density-functional theory (RT-TDDFT) is one of the most practical techniques available to simulate electronic dynamics of molecules and materials. Promising applications of RT-TDDFT to study nonlinear spectra and energy transport demand simulations of large solvated systems over long time scales, which are computationally quite costly. In this paper, we apply an embedding technique developed for ground-state SCF methods by Manby and Miller to accelerate realtime TDDFT. We assess the accuracy and speed of these approximations by studying the absorption spectra of solvated and covalently split chromophores. Our embedding approach is also compared with less accurate, less costly QM/MM charge embeddings. We find that by mixing levels of detail the embedded mean-field theory scheme is a simple, accurate, and effective way to accelerate RT-TDDFT simulations.