Mineral cleavage nature and surface energy: Anisotropic surface broken bonds consideration

The population of surface broken bonds of some typical sulfide, oxide and salt-type minerals which may belong to cubic, tetragonal, hexagonal, or orthorhombic system, were calculated. In terms of the calculation results, the cleavage natures of these minerals were analyzed, and the relationship between surface broken bonds density and surface energy was also established. The results show that the surface broken bonds properties could be used to predict the cleavage nature of most of minerals, and the predicted cleavage planes agree well with those reported in previous literature. Moreover, this work explored a rule that, surface broken bonds density is directly related to surface energy with determination coefficient（R2） of over 0.8, indicating that the former is a dominant factor to determine the latter. Therefore, anisotropic surface broken bonds density can be used to predict the stability of mineral surface and the reactivity of surface atoms.

Diffusion Monte Carlo Study of Bond Dissociation Energies for BH2, B（OH）2, BCl2, and BCI

On basis of bond dissociation energies （BDEs） for BH2, B（OH）2, BCl2, and BCl, the diffusion Monte Carlo （DMC） method is applied to explore the BDEs of HB-H, HOB-OH, ClB-Cl, and B-Cl. The effect of the choice of orbitals, as well as the backflow transformation, is studied. The Slater-Jastrow DMC algorithm gives BDEs of 359.1±0.12 kJ/mol for HB-H, 410.5±0.50 kJ/mol for HOB-OH, 357.8±1.46 kJ/mol for ClB-Cl, and 504.5±0.96 kJ/mol for B-Cl using B3PW91 orbitals and similar BDEs when B3LYP orbitals are used. DMC with backflow corrections （BF-DMC） gives a HB-H BDE of 369.9±0.12 kJ/mol which is close to one of the available experimental value （375.8 kJ/mol）. In the case of HOB-OH BDE, the BF-DMC calculation is 446.04-1.84 k J/mol that is closer to the experimental BDE. The BF-DMC BDE for ClB-Cl is 343.2±2.34 kJ/mol and the BF-DMC B-Cl BDE is 523.3±0.33 kJ/mol, which are close to the experimental BDEs, 341.9 and 530.0 kJ/mol, respectively.

The evaluation of bond dissociation energies for NO2 scission in nitro compounds using density functional and complete basis set methods

By using the density functional theory （B3LYP） and four highly accurate complete basis set （CBS-Q, CBS-QB3, CBS-Lq, and CBS-4M）ab initio methods, the X（C, N, O）-NO2 bond dissociation energies （BDEs） for CH3NO2, C2H3NO2, C2H5NO2, HONO2, CH3ONO2, C2H5ONO2, NH2NO2 （CH3）2NNO2 are computed. By comparing the computed BDEs and experimental results, it is found that the B3LYP method is unable to predict satisfactorily the results of bond dissociation energy （BDE）; however, all four CBS models are generally able to give reliable predication of the X（C, N, O）-NO2 BDEs for these nitro compounds. Moreover, the CBS-4M calculation is the least computationally demanding among the four CBS methods considered, Therefore, we recommend CBS-4M method as a reliable method of computing the BDEs for this nitro compound system.

Interfacial coordination bonds accelerate charge separation for unprecedented hydrogen evolution over S-scheme heterojunction

Inspired by natural photosynthesis,fabricating high-performance S-scheme heterojunction is regarded as a successful tactic to address energy and environmental issues.Herein,NH_(2)-MIL-125(Ti)/Zn_(0.5)Cd_(0.5)S/NiS(NMT/ZCS/NiS)S-scheme heterojunction with interfacial coordination bonds is successfully synthesized through in-situ solvothermal strategy.Notably,the optimal NMT/ZCS/NiS S-scheme heterojunction exhibits comparable photocatalytic H_(2)evolution(PHE)rate of about 14876.7μmol h^(−1)g^(−1)with apparent quantum yield of 24.2%at 420 nm,which is significantly higher than that of recently reported MOFs-based photocatalysts.The interfacial coordination bonds(Zn–N,Cd–N,and Ni–N bonds)accelerate the separation and transfer of photogenerated charges,and the NiS as cocatalyst can provide more catalytically active sites,which synergistically improve the photocatalytic performance.Moreover,theoretical calculation results display that the construction of NMT/ZCS/NiS S-scheme heterojunction also optimize the binding energy of active site-adsorbed hydrogen atoms to enable fast adsorption and desorption.Photoassisted Kelvin probe force microscopy,in-situ irradiation X-ray photoelectron spectroscopy,femtosecond transient absorption spectroscopy,and theoretical calculations provide sufficient evidence of the S-scheme charge migration mechanism.This work offers unique viewpoints for simultaneously accelerating the charge dynamics and optimizing the binding strength between the active sites and hydrogen adsorbates over S-scheme heterojunction.

Quantum chemical calculations of bond dissociation energies for COOH scission and electronic structure in some acids

Quantum chemical calculations are performed to investigate the equilibrium C-COOH bond distances and the bond dissociation energies（BDEs） for 15 acids.These compounds are studied by utilizing the hybrid density functional theory（DFT）（B3LYP,B3PW91,B3P86,PBE1PBE） and the complete basis set（CBS-Q） method in conjunction with the 6311G^＊＊ basis as DFT methods have been found to have low basis sets sensitivity for small and medium molecules in our previous work.Comparisons between the computational results and the experimental values reveal that CBS-Q method,which can produce reasonable BDEs for some systems in our previous work,seems unable to predict accurate BDEs here.However,the B3P86 calculated results accord very well with the experimental values,within an average absolute error of 2.3 kcal/mol.Thus,B3P86 method is suitable for computing the reliable BDEs of C-COOH bond for carboxylic acid compounds.In addition,the energy gaps between the highest occupied molecular orbital（HOMO） and the lowest unoccupied molecular orbital（LUMO） of studied compounds are estimated,based on which the relative thermal stabilities of the studied acids are also discussed.

Peripheral carbazole units-decorated MR emitter containing B−N covalent bond for highly efficient green OLEDs with low roll-off

Boron−nitrogen doped multiple resonance(BN-MR)emitters,characterized by B−N covalent bonds,offer distinctive advantages as pivotal building blocks for facile access to novel MR emitters featuring narrowband spectra and high efficiency.However,there remains a scarcity of exploration concerning synthetic methods and structural derivations to expand the library of novel BN-MR emitters.Herein,we present the synthesis of a BN-MR emitter,tCz[B−N]N,through a one-pot borylation reaction directed by the amine group,achieving an impressive yield of 94%.The emitter is decorated by incorporating two 3,6-di-tbutylcarbazole(tCz)units into a B−N covalent bond doped BN-MR parent molecule via para-C−π−D and para-N−π−D conjugations.This peripheral decoration strategy enhances the reverse intersystem crossing process and shifts the emission band towards the pure green region,peaking at 526 nm with a narrowband full-width at half maximum(FWHM)of 41 nm.Consequently,organic light emitting diodes(OLEDs)employing this emitter achieved a maximum external quantum efficiency(EQEmax)value of 27.7%,with minimal efficiency roll-off.Even at a practical luminance of 1000 cd·m^(−2),the device maintains a high EQE value of 24.6%.

Density Functional Calculations of C–NO_2 Bond Dissociation Energies for Nitroalkanes Molecules

Bond dissociation energies for the removal of nitrogen dioxide group in some nitroalkane energetic materials have been calculated by using the three hybrid density functional theory （DFT） methods B3LYP, B3PW91 and B3P86 with 6-31g^＊＊ and 6-311g^＊＊ basis sets. The computed BDEs have been compared with the available experimental results. It is found that the B3P86 method with 6-31g^＊＊ and 6-311g^＊＊ basis sets can obtain satisfactory bond dissociation energies （BDEs）, which are in extraordinary agreement with the experimental data. Considering the smaller mean absolute deviation and maximum difference, the reliable B3P86/6-311g^＊＊ method was recommended to compute the BDEs for the removal of nitrogen dioxide group in the nitroalkane energetic materials. Using the method, the BDEs of 8 other nitroalkane energetic materials have been calculated and the maximum difference from experimental value is 1.76 kcal.mo1^-1 （for the BDE of tC4Hg-NOz）, which further proves the reliability of B3P86/6-311g^＊＊ method. In addition, it is noted that the BDEs of C-NO2 bond change slightly for main chain nitroalkane compounds with the maximum difference of only 3.43 kcal mo1^-1.

Theoretical Study of the N-NO_2 Bond Dissociation Energies for Energetic Materials with Density Functional Theory

The N-NO2 bond dissociation energies （BDEs） for 7 energetic materials were computed by means of accurate density functional theory （B3LYP, B3PW91 and B3P86） with 6-31G＊＊ and 6-311G＊＊ basis sets. By comparing the computed energies and experimental results, we find that the B3P86/6-311G＊＊ method can give good results of BDE, which has the mean absolute deviation of 1.30kcal/mol. In addition, substituent effects were also taken into account. It is noted that the Hammett constants of substituent groups are related to the BDEs of the N-NO2 bond and the bond dissociation energies of the energetic materials studied decrease when increasing the number of NO2 group.

Study on the optimal incident proton energy of ^(7)Li(p,n)^(7)Be neutron source for boron neutron capture therapy

Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear reaction.Among various neutron sources,accelerator-based sources have emerged as particularly promising for BNCT applications.The^(7)Li(p,n)^(7)Be reaction is highly regarded as a potential neutron source for BNCT,owing to its low threshold energy for the reaction,significant neutron yield,appropriate average neutron energy,and additional benefits.This study utilized Monte Carlo simulations to model the physical interactions within a lithium target subjected to proton bombardment,including neutron moderation by an MgF_(2)moderator and subsequent BNCT dose analysis using a Snyder head phantom.The study focused on calculating the yields of epithermal neutrons for various incident proton energies,finding an optimal energy at 2.7 MeV.Furthermore,the Snyder head phantom was employed in dose simulations to validate the effectiveness of this specific incident energy when utilizing a^(7)Li(p,n)^(7)Be neutron source for BNCT purposes.

Bonding Energies and Structural Study of Alkylaluminium

Neutral aluminium alkyls are well known to act as ethylene oligomerization and polymerization catalysts and cocatalysts.On the basis of the full optimization of alkylaluminium compounds with Gaussian 98 program package at the B3LYP/6-31G＊＊ level,the selected structures and bonding energies were investigated extensively.The geometries and bonding energies of AlR3（R = H,CH3,C2H5,C3H7,C4H9） and Al（C2H5）2R＇（R＇ = C2H5,C3H7,C4H9,C5H11,C6H13） were investigated extensively,and we found that,along with the prolongation of carbon chains the terminal C-C bond is shortened gradually until to a constant value of about 0.1532 nm in C4H9;and the bonding energy almost remains constant.The dative bonding of C2H4 to Al（C2H5）3,whose bonding energy is only 15.30 kJ/mol,is very weak.

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.

Bonding Energy and Growth Habit of Lithium Niobate Single Crystals

On the basis of crystallographic structure of lithium niobate (LN), the bonding energy was quantitatively calculated by the bond valence sum model, which was employed to investigate the crystal growth. A possible relationship between the crystal growth habit and chemical bonding energy of LN crystals are found. It is found that the higher the bond energy, the slower the growth rate, and the more important the plane. The analytical results indicate that (012) plane is the most influential face for the LN crystal growth, which consists well with the standard card (JCPDS Card: 20-0631) and our previous experimental observation. The current work shows that the chemical bond analysis of LN crystals allows us to predict its growth habit and thus to obtain the expected morphology during the spontaneous growth.

Changing Rules of Bonding Electron Pair Correlation Energies of CH_3X (X=F,OH,NH_2) Systems

The pair correlation energy of bonding electrons is used and analyzed in the cal- culation of CH and CY (Y = F, O, N) bonding electron pairs in CH3X (X = F, OH, NH2) isoelec- tronic systems based on intra- and interpair correlation energy results at both MP2-OPT2/6- 311++G(d) and MP2-OPT2/cc-pVtz levels with MELD program. Comparison of two set results shows that cc-pVtz and 6-311++G(d) give more correlation energy of valence electrons and innermost core electron pairs, respectively in these systems, resulting that the total correlation energy with cc-pVtz basis of each system is larger than that with 6-311++G(d). Investigations of pair correlation energy show that with the decrease of electronegativity of X atom and the increase of H atoms in these CH3X (X = F, OH, NH2) systems, the pair correlation energy of 1sC2 of the C atoms is transferable, and the correlation energy of CH bonding electron pair with little changes is of approximate transferability, while those of CY (CF, CO, CN) bonding electron pair decrease in a large extent from CH3F through CH3OH to CH3NH2 molecules. It is suggested that the study of pair correlation energy of bonding electrons will further deepen the understanding of electron corre- lation effect from traditional chemical bonding concept.

Hot embossing of micro energy director for micro polymer fusion ultrasonic bonding

In order to use micro ultrasonic bonding technique to package polymer microfluidic chips, an auxiliary microstructure named micro energy director is designed and fabricated. The hot embossing process for PMMA （ polymethyl methacrylate） substrates with both concave micro channel and convex micro energy director for ultrasonic bonding is studied. The embossing processes with different embossing temperatures are simulated using Finite Element Method （FEM）. The optimized parameters are： the embossing temperature of 135 ℃ , holding time of 200 s, and the embossing pressure of 1.65 MPa. The experimental results show that the replication error between experiments and simulations is less than 2% and the replication accuracy of the microstrueture is more than 96%. The study offers a method for quick optimizing parameters for hot embossing both concave and convex microstructures.

Bonding Energy of a Molecular Orbital(Ⅱ)——Ab initio Calculation

Calculation of the bonding energy of a molecular orbital for a series of small molecules has been carried out by using ab initio STO-3G method. The results obtained demonstrate that the concept of the molecular orbital bonding energy is applicable for judging whether a molecular orbital is bonding, nonbonding or antibonding besides Mulliken overlap criterion.

Average Bond Energy and Fermi Level on Free Electronic Band Model

On the basis of free-electronic bands, the Fermi energy is calculated by summing the band eigenvalues over Brillouin-zones ,and the results may lead to understand the physical basis of the average-bond-energy model in the calculation of valence-band offsets.

STUDIES ON PROCESS AND STABILITY OF BONDED Sm_2TM_(17)MAGNETS WITH HIGH COERCIVITY AND HIGH ENERGY PRODUCT

The process of the epoxy-bonded Sm_2TM_(17) magnets includes:(1)after melting,the ingots are treated by solid soluiion,and then aged and pulverized;(2)the obtained alloy powder is mixed with epoxy resin bind- er;(3)the mixture is pressed in a magnetic field;(4)the compacts are cured.When the SmCo_(4.9)Fe_(2.7)Cu_(0.54)Zr_(0.13) alloy is heat treated and pressed with optimum pressing parameters,the high quality bonded magnets with B_r=8250 G,_iH_c=13000 Oe,and(BH)_(max)=16MGOe can be obtained.The stability of the magnets is studied also.The irreversible loss of O.C.(open circuit)remanence B_r in the temperature range between 25 and 150℃,is less than 4%.The average temperature coefficient at temperatures between 25 and 70℃ is-0.03%/℃.The magnets obtained have heat resistance up to 130℃ even in long-term service, and have good corrosion resistance in acid,alkali and salt solutions.

Estimation of Intramolecular Hydrogen-bonding Energy via the Substitution Method

The intramolecular hydrogen-bonding energies for eighteen molecules were calculated based on the substitution method, and compared with those predicted by the cis-trans method. The energy values obtained from two methods are close to each other with a correlation coefficient of 0.96. Furthermore, the hydrogen-bonding energies based on the substitution method are consistent with the geometrical features of intramolecular hydrogen bonds. Both of them demonstrate that the substitution method is capable of providing a good estimation of intramolecular hydrogen-bonding energy.