Theoretical study on the lithium bond interaction of furan homologues C_4H_4Y (Y=O, S) with LiCH_3 via DFT and MP2

The optimizations geometries and interaction energy corrected by BSSE of the complexes between C4H4Y (Y=O, S) and CH3Li have been calculated at the B3LYP/6-311 G** and MP2/6-311 G** levels. Three complexes were obtained. Abnormally, the calculations showed that all the C10—Li14 bond lengths increased obviously but the blue-shift of C10—Li14 stretching frequency occurred after formed complexes. The calculated binding energy with basis set super-position error (BSSE) and zero-point vibrational energy corrections of complexes I―III is ?45.757, ?35.700 and ?39.107 kJ·mol?1, respectively. The analyses on the combining interaction with the atom-in-molecules theory (AIM) also showed that a relatively strong lithium bond interaction presented in furan homologues C4H4Y---LiCH3 systems. Natural bond orbital theory (NBO) analysis has been performed, and the results revealed that the com- plex I is formed with n-σ type lithium bond interaction between C4H4O and LiCH3, complex II is formed with π-s type lithium bond interaction between C4H4O and LiCH3, and complex III is formed with π-s and n-s type lithium bond interactions between C4H4S and LiCH3, respectively.     

Lithium bond structures of H_nY (n=2, 3; Y=O, S, N)… LiNH_2 and the abnormal blue shift of N―Li bond

The optimized geometries of the complexes between HnY (n=2, 3; Y=O, S, N) and LiNH2 have been calculated at the B3LYP/6-311 G** and MP2/6-311 G** levels. Three stable complexes were obtained. Frequency analysis showed that the enlarged 2N―4Li presents the abnormal blue shift in three complexes. The calculated binding energy with basis set super-position error (BSSE) and zero-point vibrational energy (ZPE) corrections of complex I―III is _58.65, _31.66 and _69.59 kJ·mol-1 (MP2), respectively. Natural bond orbital theory (NBO) analysis has been performed, and the results revealed that the H2O…LiNH2 (complex I) and H3N…LiNH2 (complex III) are formed with coexisting σ-s and n-s type lithium bond interactions, complexⅡis formed with π-s type lithium bond interaction between HnY (n=2,3; Y=O, N) and LiNH2, and H2S…LiNH2 (complex II) is formed with n-s type lithium bond interaction between H2S and LiNH2. Natural resonance theory (NRT) and atom in molecule (AIM) theory have also been studied to investigate the bond order and topological properties of the lithium bond structures.     

Theoretical study of N(C)―H…H―B multi-dihydrogen bonds

The optimized geometries, frequencies and interaction energy corrected with basis set superposition error (BSSE) of the multi-dihydrogen bond complexes C₄H₄NH…BH₄^–. and CH≡CH…BH₄^–. have been calculated at both the B3LYP/6-311++G** and the MP2/6-311++G** levels. The calculations were per-formed to study the nature of the N―H…H3―B and C―H…H2―B red shift multi dihydrogen bond in complex C4H4NH…BH^–₄ and CH≡CH…BH4–. The BSSE-corrected multi-dihydrogen bond interaction en-ergy of complex I (C₄H₄NH…BH₄^–.) and complexⅡ(CH≡CH…BH₄^–.) is -76.62 and -33.79 kJ/mol (MP2/6- 311++G**), respectively. From the natural bond orbital（NBO）analysis, we detailedly discussed the orbital interactions, electron density transfers, rehybridizations and the essential of the correlative bond length changes in the two complexes. In addition, solvent effect on the geometric structures, vibration frequencies and interaction energy of the monomer and complexes was studied in detail. It is relevant to the relatively dielectric constants (ε).     

Theoretical characterization of single-electron iodine-bond weak interactions in CH3…I-Y（Y=BH2,H,CH3,C2H3,C2H,CN,NC）systems

Iodine-involved single-electron halogen bonds (SEXBs) weak interactions in the systems of CH3···I-Y(Y = BH2, H, CH3, CH==CH2, C≡CH, CN, NC) were investigated for the first time using B3LYP/6-311++G(d,p) and MP2/aug-cc-pVTZ computational levels (the relativistic effective core potential basis set of Lanl2dz was used on iodine atom). The interaction energies between two moieties with basis set super-position error corrections for the seven complexes are -0.57, -1.36, -3.80, -2.17, -4.49,-6.33 and -8.64 kJ mol-1 (MP2/aug-cc-pVTZ ), respectively, which shows that SEXBs interactions are all weak. Natural bond orbital theory analysis revealed that charges flow from CH3 to the I-Y moiety. The total amount of natural bond orbital charge transfer (ΔNC) from the CH3 radical to I-Y increases in the order CH3…IBH2 < CH3…IH ≈ CH3…ICH3 ≈ CH3···IC2H3 < CH3…ICCH< CH3…ICN< CH3…INC. Atoms-in-molecules theory was used to investigate the topological properties of the bond critical points in the seven SEXB structures.     

Theoretical study on the lithium bond interaction of furan homologues C4H4Y （Y=O,S） with LiCH3 via DFT and MP2

The optimizations geometries and interaction energy corrected by BSSE of the complexes between C4H4Y （Y=O, S） and CHiLi have been calculated at the B3LYP/6-311＋＋G^＊＊ and MP2/6-311＋＋G^＊＊ levels. Three complexes were obtained. Abnormally, the calculations showed that all the C10--Li14 bond lengths increased obviously but the blue-shift of C10-Li14 stretching frequency occurred after formed complexes. The calculated binding energy with basis set super-position error （BSSE） and zero-point vibrational energy corrections of complexes I-III is -45.757, -35.700 and -39.107 kJ·mol^-1, respectively. The analyses on the combining interaction with the atom-in-molecules theory （AIM） also showed that a relatively strong lithium bond interaction presented in furan homologues C4H4Y-LiCH3 systems. Natural bond orbital theory （NBO） analysis has been performed, and the results revealed that the complex I is formed with n-σ type lithium bond interaction between C4H40 and LiCH3, complex II is formed with TT-s type lithium bond interaction between C4H4O and LiCH3, and complex III is formed with TT-s and n-s type lithium bond interactions between C4H4S and LiCH3, respectively.     

Weak interaction between CH3SO and HOCl: Hydrogen bond, chlorine bond and oxygen bond

B3lyp/6-311＋＋g＊＊ and mp2/6-311＋＋g＊＊ calculations were used to analyze the interaction between CH3SO and HOCl. Nine （complex A： S1A-S9A） and five （complex B： S4B-S7B and S10B） minima were localized on the potential energy surface of CH3SO…HOCl complexes at b3lyp/6-311＋＋g＊＊ and mp2/ 6-311＋＋g＊＊ computational levels, respectively. The AIM and NBO theories were also applied to explain the nature of the complexes. Bonding energy of complexes A and B corrected with BSSE falls in the ranges of -0.4―-41.4 kJ·mol-1 and -6.9―-35.8 kJ·mol-1 at mp2/6-311＋＋g＊＊ level, respectively. The re- sults show that a novel oxygen bond complex （S6） exists in the system, besides hydrogen bond and chlorine bond. Especially, S6B-F, S6B-Br and S7B are blue shifted complexes compared with red shifted S6A, because the electron transfer occurs between LP1（S8） and σ＊（O5-Cl7）, resulting in the increase of O5-Cl7 and the decrease of vibrational frequency. The complex of S10B has characteristics of both red shift and blue shift.     

Lithium bond structures of HnY （n=2, 3; Y=O,S, N）…LiNH2 and the abnormal blue shift of N-Li bond

The optimized geometries of the complexes between HnY （n=2, 3; Y=O, S, N） and LiNH2 have been calculated at the B3LYP/6-311＋＋G^＊＊ and MP2/6-311＋＋G^＊＊ levels. Three stable complexes were obtained. Frequency analysis showed that the enlarged 2N-4Li presents the abnormal blue shift in three complexes. The calculated binding energy with basis set super-position error （BSSE） and zero-point vibrational energy （ZPE） corrections of complex Ⅰ-Ⅲ is -58.65, -31.66 and -69.59 kJ·mol^-1 （MP2）, respectively. Natural bond orbital theory （NBO） analysis has been performed, and the results revealed that the H2O…LiNH2 （complex I） and H3N…LiNH2 （complex Ⅲ） are formed with coexisting σ-s and n-s type lithium bond interactions, complex Ⅱ is formed with ττ-s type lithium bond interaction between HnY （n=2,3; Y=O, N） and LiNH2, and H2S…LiNH2 （complex Ⅱ） is formed with n-s type lithium bond interaction between H2S and LiNH2. Natural resonance theory （NRT） and atom in molecule （AIM） theory have also been studied to investigate the bond order and topological properties of the lithium bond structures.     

Prediction of Liquid-Liquid Equilibrium Using the Group Solubility Parameter Model

The group solubility parameter （GSP） model was used to analyze the liquid-liquid equilibrium （LLE） of ternary and quaternary systems. The GSP parameters are divided into four dimensions representing the four major intermolecular forces. The values of the parameters were determined by regression using the nonlinear SIMPLEX optimization method to fit the LLE data of 548 ternary and 26 quaternary systems selected from the literature. LLE predictions of 8 ternary systems were then made using the fit parameters. Comparison of the results with predictions using the modified UNIFAC model shows that the GSP model has less adjustable parameters to achieve a similar accuracy and that the parameter values are easily acquired by analysis of available data.     

Effect of lattice defects on the electronic structures and floatability of pyrites

The electronic structures of three types of lattice defects in pyrites (i.e., As-substituted, Co-substituted, and intercrystalline Au pyrites) were calculated using the density functional theory (DFT). In addition, their band structures, density of states, and difference charge density were studied. The effect of the three types of lattice defects on the pyrite floatability was explored. The calculated results showed that the band-gaps of pyrites with Co-substitution and intercrystalline Au decreased significantly, which favors the oxidation of xanthate to dixanthogen and the adsorption of dixanthogen during pyrite flotation. The stability of the pyrites increased in the following order:As-substituted < perfect < Co-substituted < intercrystalline Au. Therefore, As-substituted pyrite is easier to be depressed by intensive oxidization compared to perfect pyrite in a strongly alkaline medium. However, Co-substituted and intercrystalline Au pyrites are more difficult to be depressed compared to perfect pyrite. The analysis of the Mulliken bond population and the electron density difference indicates that the covalence characteristic of the S-Fe bond is larger compared to the S-S bond in perfect pyrite. In addition, the presence of the three types of lattice defects in the pyrite bulk results in an increase in the covalence level of the S-Fe bond and a decrease in the covalence level of the S-S bond, which affect the natural floatability of the pyrites.     

Investigation of Highly Designable Dented Structures in HP Model with Hydrogen Bond Energy

Some highly designable protein structures have dented on the surface of their native structures, and are not full compactly folded. According to hydrophobic-polar （HP） model the most designable structures are full compactly folded. To investigate the designability of the dented structures, we introduce the hydrogen bond energy in the secondary structures by using the secondary-structure-favored HP model proposed by Ou-yang etc. The result shows that the average designability increases with the strength of the hydrogen bond. The designabilities of the structures with same dented shape increase exponentially with the number of secondary structure sites. The dented structures can have the highest designabilities for a certain value of hydrogen bond energy density.     

Investigation of adsorption of surfactant at the air-water interface with quantum chemistry method

Density functional theory （DFT） of quantum chemistry was used to optimize the configuration of the anionic surfactant complexes CH3（CH2）7OSO3^- （H2O）n （n=0-6） and calculate their molecular frequencies at the B3LYP/6-311＋G^＊ level. The interaction of CH3（CH2）7OSO3^- with 1 to 6 water molecules was investigated at the air-water interface with DFT. The results revealed that the hydration shell was formed in the form of H-bond between the hydrophilic group of CH3（CH2）7OSO3^- and 6 waters. The strength of H-bonds belongs to medium. Binding free energy revealed that the hydration shell was stable. The increase of the number of water molecules will cause increases of the total charge of hydrophilic group and S10-O9-C8 bond angle, but decreases of the alkyl chain length and the bond lengths of S10-O11, S10-O12 as well as S10-O13, respectively.     

Effect of Nano-SiC and Nano-Si Doping on Critical Current Density of MgB_2

The discovery of superconductivity in magnesium diboride (MgB2) has opened up a new field in materials science research. It offers a possibility of a new class of high performance superconducting materials for practical applications because of the relatively low cost of fabrication, high critical current densities (Jc) and fields, large coherence length, absence of weak links, higher Tc(TC = 39K) compared with Nb3Sn and Nb-Ti alloys (two or four times that of Nb,,Sn and Nb-Ti alloys). However, the weak flux pinning in the magnetic field remains a major challenge. This paper reports the most interesting results on nanomaterial (SiC and Si) doping in magnesium diboride. The high density of nano-scale defects introduced by doping is responsible for the enhanced pinning. The fabrication method, critical current density, microstructures, flux pinning and cost for magnesium diboride bulks, wires and tapes are also discussed. It is believed that high performance SiC doped MgB2 will have a great potential for m     

Mechanism of Kenaf Retting Using Aerobes

The experimental results showed that the duration of microbial retting processing of kenaf fibers by using aerobic microbe was four times shorter than that by using anaerobic microbe. The residual gum percentage, breaking strength, breaking elongation and linear density of aerobic retted kenaf bundle fibers did not show significantly difference with that of anaerobic retted kenaf bundle fibers by ANOVA-Tukey's studentized test at a = 5% except for the softness. The bioenergetic principle and the calculation of the amount of ATP produced during the decomposition processing of kenaf gums were used to explain why the retting duration in the case of using aerobic microbes was much shorter than that of using anaerobic microbes.     

First-principles investigation of the alloying effect of Ta and W on γ -TiAl

The alloying effect of the refractory elements Ta and W on the electronic structure of y-T\A\ is investigated by using the first-principles discrete variational method within the framework of density functional theory. The impurity formation energy result indicates that Ta and W can stay steadily in the TiAl system by way of substitution. The Mulliken population, density of states and charge density difference results show that Ta and W both give rise to the strong interaction between themselves and the neighboring host atoms. The alloying effect of the two elements onγ-TiAl is the same.     

Comparison and analysis of dislocation density, morphology and evolution in microstructure of low-carbon steel produced using different technologies

Three kinds of specimens were produced from hot strips of similar composition and same thickness （nominal gauge 4.0 mm） but produced using different technologies, and the dislocation density of these strips was quantitatively measured by positron annihilation technique test. The dislocation morphology and evolution in microstructure of each pass for producing the 1.9 mm hot strip using CSP （compact strip production） technology were observed under an H-800 transmission electron microscope; its density was also quantitatively measured using the positron annihilation technique test, and the factors influencing the dislocation density during the production process were analyzed. The experimental results show that the dislocation density in the microstructure produced using CSP technology is higher than that in the microstructure produced using conventional technology. This result was discussed and confirmed on the basis of the finite element simulation and the theory relevant to dislocations.     

Structural dependences of the η~6 complexes of 3-amino-9-ethylcarbazole with chromium tricarbonyl fragment on third-order optical nonlinearities

Degenerate four-wave mixing measurements, using the 35 ps pulses at 532 nm, have been employed to investigate the third-order nonlinear optical parameters of two chromium tricarbonyl complexes η6-bonded to 3-amino-9-ethylcarbazole at either the NH2-substituted aryl ring (1) or the unsubstituted ring (2) and their precursor 3-amino-9-ethylcarbazole (AECz). The second-order hyperpolarizability γ of the compounds 1 and 2 were found to be 42.9×10-31 and 35.9×10-31 esu, respectively, approximately one order of magnitude greater than AECz. The relation between the molecular structure and second-order hyperpolarizability of the compounds 1 and 2 was explored in detail based on the three-level model and the density functional theory (DFT) calculation. The theoretical results indicate that the spatial distri-bution of electron density has the profound role in the third-order nonlinear optical properties.     

Structural dependences of the <Emphasis Type="Italic">η</Emphasis><Superscript>6</Superscript> complexes of 3-amino-9-ethylcarbazole with chromium tricarbonyl fragment on third-order optical nonlinearities

Degenerate four-wave mixing measurements, using the 35 ps pulses at 532 nm, have been employed to investigate the third-order nonlinear optical parameters of two chromium tricarbonyl complexes η6-bonded to 3-amino-9-ethylcarbazole at either the NH2-substituted aryl ring （1） or the unsubstituted ring （2） and their precursor 3-amino-9-ethylcarbazole （AECz）. The second-order hyperpolarizability y of the compounds 1 and 2 were found to be 42.9×10^-31 and 35.9×10^-31 esu, respectively, approximately one order of magnitude greater than AECz. The relation between the molecular structure and second-order hyperpolarizability of the compounds I and 2 was explored in detail based on the three-level model and the density functional theory （DFT） calculation. The theoretical results indicate that the spatial distribution of electron density has the profound role in the third-order nonlinear optical properties.     

Antibacterial Activity and Structure-Activity Relationships of Schiff Bases on Staphylococcus aureus by Microcalorimetry

The growth of Staphylococcus aureus under the action of six kinds of Schiff bases(A,B,C,D,E,F) was studied by means of microcalorimetry. Growth constant k and inhibition ratio I were calculated. Also,the antibacterial activity,the action characteristics and the structure-activity relationships of the compounds on S. aureus were analyzed. Results indicate that B,F show good antibacterial activity(IC50:293.6 mg · L-1 and 307.8 mg · L-1) ,D,E show moderate antibacterial activity(IC50:966.3 mg · L-1 and 1 126.7 mg · L-1) ,and A,C just show weak antibacterial activity(IC50 1 200 mg · L-1) . The I-c curves mainly present a straight line shape for B,D,E and F,but an inverse "S" shape for A and C. Structure-activity relationships analysis suggests that the species and position of the substituents determine the antibacterial activity of these Schiff bases,and the charge density distribution is one of the most important influencing factors.     

Enrichment of copper and recycling of cyanide from copper–cyanide waste by solvent extraction

The enrichment of copper from copper–cyanide wastewater by solvent extraction was investigated using a quaternary ammonium salt as an extractant. The influences of important parameters, e.g., organic-phase components, aqueous pH values, temperature, inorganic anion impurities, CN/Cu molar ratio, and stripping reagents, were examined systematically, and the optimal conditions were determined. The results indicated that copper was effectively concentrated from low-concentration solutions using Aliquat 336 and that the extraction efficiency increased linearly with increasing temperature. The aqueous pH value and concentrations of inorganic anion impurities only weakly affected the extraction process when varied in appropriate ranges. The CN/Cu molar ratio affected the extraction efficiency by changing the distribution of copper–cyanide complexes. The difference in gold leaching efficiency between using raffinate and fresh water was negligible.     

Effect of Nano－SiC and Nano－Si Doping on Critical Current Density of MgB2

The discovery of superconductivity in magnesium diboride (MgB2) has opened up a new field in materials science research. It offers a possibility of a new class of high performance superconducting materials for practical applications because of the relatively low cost of fabrication, high critical current densities (Jc)and fields, large coherence length, absence of Weak links, higher Tc (Tc = 39 K) compared with Nb3Sn and Nb-Ti alloys (two or four times that of Nb3Sn and Nb-Ti alloys). However, the weak flux pinning in the magnetic field remains a major challenge. This paper reports the most interesting results on nenomaterial (SiC and Si) doping in magnesium diboride. The high density of nano-scele defects introduced by doping is responsible for the enhanced pinning. The fabrication method, critical current density, microstructures, flux pinning and cost for magnesium diboride bulks, wires and tapes are also discussed. It is believed that high performance SiC doped MgB2 will have a great potential for many practical applications at 5K to 25K up to 5T.