Recent progress on discovery and properties prediction of energy materials:Simple machine learning meets complex quantum chemistry

In nature,the properties of matter are ultimately governed by the electronic structures.Quantum chemistry(QC)at electronic level matches well with a few simple physical assumptions in solving simple problems.To date,machine learning(ML)algorithm has been migrated to this field to simplify calculations and improve fidelity.This review introduces the basic information on universal electron structures of emerging energy materials and ML algorithms involved in the prediction of material properties.Then,the structure-property relationships based on ML algorithm and QC theory are reviewed.Especially,the summary of recently reported applications on classifying crystal structure,modeling electronic structure,optimizing experimental method,and predicting performance is provided.Last,an outlook on ML assisted QC calculation towards identifying emerging energy materials is also presented.

Solvothermal Syntheses, Crystal Structures, Thermal Stability and Quantum Chemistry of Dinuclear Trialkyltin Complexes Constructed by Camphoric Acid

Two dinuclear organotin complexes C8H14（CO2SnCy3）2（1）（Cy = cyclohexyl group） and C8H14[CO2Sn（CH2CMe2Ph）3]2（2） were synthesized by the reactions of camphoric acid with tricyclohexyltin hydroxide and bis[tri（2-methyl-2-phenyl）propyltin] oxide under solvothermal conditions, and these complexes were characterized by infrared spectra, elemental analyses, and H NMR spectra. The crystal of 1 belongs to the monoclinic system, space group P21/c with a = 1.83478（19）, b = 1.52707（18）, c = 1.9849（2） nm, β = 122.515（7）°, Z = 4, V = 4.6896（9） nm^3, Dc = 1.324 g/cm^3, μ（MoKα） = 1.103 mm^-1, F（000） = 1952, R = 0.0697 and wR = 0.2040. In addition, thermal stability and quantum chemical calculation of 1 were also studied.

Formation Mechanism of Biomass Aromatic Hydrocarbon Tar on Quantum Chemistry

The formation process of aromatic hydrocarbon tar during the pyrolysis process of biomass components of cel-lulose and lignin was carried out by quantum chemical calculation based on density functional theory method B3LYP/6-31G++(d,p).5 Hydroxymethylfurfural was chosen as the model compound of cellulose and hemicel-lulose,and syringa ldehyde was chosen as the model compound of lignin.The calculation results show that the formation process of cellulose monocyclic aromatic hydrocarbon tar is the conversion process of benzene ring from furan ring,and the highest reaction energy barrier appears in the process of decarbonylation,which is 370.8 kJ/mol.The formation of lignin monocyclic aromatic hydrocarbon tar is mainly the process of side chains removal and the formation of phenol,The highest reaction energy barrier appears in the process of decarbonyla-tion,which is 374.9 kJ/mol.The reaction mechanism of phenanthrene formation from naphthalene was selected as the formation of cellulose and lignin polycydic aromatic hydrocarbon tar.The calculation results show that he total barrier of the pathway that naphthalene dehydrogenates to form naphthalene free radicals and then reacts with ethylene twice by addition action,finally occurs cydization reactions and isomerizes to produce phenan-threne is lowest,that is 38.6 kJ/mol.So it is proved that the evolution of tar is the process of deoxygenation and cyclization with the increase of the temperature from a theoretical point of view.

A Benzimidazole-pyridine-2,3-dicarboxylic Acid Bridged Zinc(Ⅱ)Coordination Complex–crystal Structure,Quantum Chemistry and Luminescence

The structure of a zinc（Ⅱ） coordination complex（1）, [C14 H10 N3 O5 Zn1.5]n or [Zn1.5（bzim）（pydc）（H2 O）]n（H2 pydc = pyridine-2,3-dicarboxylic acid, Hbzim = benzimidazole）, has been determined by X-ray crystallography and characterized by elemental analysis, IR spectrum and luminescence. Chemical formula： C14 H10 N3 O5 Zn1.5. It crystallizes in the monoclinic system, space group P21/c with a = 12.303（4）, b = 12.052（4）, c = 10.212（3） ？, β = 104.147（4）, V = 1468.3（8） ？3, Z = 4, Mr = 398.30, Dc = 1.802 g/cm3, F（000） = 800, μ = 2.501 mm-1 and S = 1.000. The 2-D network architecture of 1 is constructed from benzimidazole, zinc and pyridine-2,3-dicarboxylic acid. The quantum-chemical calculations have been performed on ‘molecular fragments’ extracted from the crystal structure using the B3 LYP method in Gaussian 09. The luminescence spectrum shows that complex 1 emits blue luminescence.

Quantum Chemistry Calculations on the Interaction Between Kaolinite and Gold

The density,function and discrete variation method (DFT - DVM) is used to study the interaction between kaolinite and gold. The correlation among the structure, chemical bond and stability is discussed. Several models are selected without gold and with gold in different directions and sites. The results show that the models with gold on the edge of kaolinite basal layer are more stable than those with gold above or under the layer, the models with gold near to [AlO2 (OH)(4)] octahedra are more stable than those with gold near to the vacancy without aluminium. The interaction between gold and the surface ions of kaolinite is strong enough to form the surface complexes.

A Quantum Chemistry Study on Structural Properties of Petroleum Resin

The geometries of resins with single-layer （SG）, double-layer （DG） and triple-layer （TG） were calculated with the quantum chemistry method. The geometries and net charges of atoms were obtained. The calculated average distances between layers were 0.5348 nm and 0.5051 nm and the action energies were -9.6355 kJ/mol and -32.2803 kJ/mol for resins DG and TG, respectively. Higher electronegative polar atoms can easily form hydrogen bonds with hydrogen atoms of other resin molecules, resulting in resin aggregates. The minimum cross-sectional diameters of resin molecules are too large to enter the pores of zeolite, so they are likely to crack on the surface of zeolite.

Neural Network Based on Quantum Chemistry for Predicting Melting Point of Organic Compounds

The melting points of organic compounds were estimated using a combined method that includes a backpropagation neural network and quantitative structure property relationship （QSPR） parameters in quantum chemistry. Eleven descriptors that reflect the intermolecular forces and molecular symmetry were used as input variables. QSPR parameters were calculated using molecular modeling and PM3 semi-empirical molecular orbital theories. A total of 260 compounds were used to train the network, which was developed using MatLab. Then, the melting points of 73 other compounds were predicted and results were compared to experimental data from the literature. The study shows that the chosen artificial neural network and the quantitative structure property relationships method present an excellent alternative for the estimation of the melting point of an organic compound, with average absolute deviation of 5%.

QUANTUM CHEMISTRY STUDIES ON THE STRENGTH PERFORMANCE OF ETTRINGITE

Ettringite is a main hydrate of cement, and the Sr-bearing ettringite is a main hydrate of Sr-bearing calcium suplhoaluminate. In this paper the two hydrates are studied by a quantum chemistry method, the self-consistent-field discrete variation X(alpha) method (SCC-DV-X(alpha)) The results show: their bond order of Al and covalent bond order of Al-O bond are alike; that the bond order of Sr and the covalent bond order of Sr-O in Sr-bearing ettringite are higher than these of ettringite is the main reason, that the strength of Sr-bearing ettringite is higher than that of ettringite.

STURCTURAL CHARACTERISTICS AND QUANTUM CHEMISTRY CALCULATION OF AI-DOPED BORON CARBIDES

Structural characteristics, chemical bonds and thermoelectric properties of Al-doped boron carbides are studied through calculations of various structural unit models by using a self-consistent-field discrete variation X. method. The calculations show that Al atom doped in boron carbide is in preference to substituting B or C atoms on the end of boron carbide chain, and then may occupy interstitial sites, but it is difficult for Al to substitute B or C atom in the centers of the chain or in the icosahedra. A representative structural unit containing an Al atom is [C - B -Al]-[B11C]-,while the structural unit without Al is [C-B-B(C)]- - [B11C]C+, and the coexistence of these two different structural units makes the electrical conductivity increased. As the covalent bond of Al-B or Al-C is weaker than that of B-B or B-C, the thermal conductivity decreases when Al is added into boron carbides. With the electrical conductivity increasing and the thermal conductivity decreases, Al doping has significant effect on thermoelectric properties of baron carbides.

Quantum Chemistry Calculation of Quercetin-silver Complex

Three possible molecular structures of quercetin-silver complexes obtained from the reaction of quercetin and Ag^＋ in equivalent molar ratio were designed and optimized by using Gaussian 98 program at the B3LYP/LanL2DZ basis set. Through theoretical analysis, one of the three designed structures is discovered to have the most stable coordination position. Then its geometry structure, natural bond orbital analyses, vibrational frequency and biological activity were performed. The results show that it has good stability and relatively stronger antioxidative activity because it is favorably attacked by O2^-. Therefore theoretical foundation is provided for the development of new quercetin metal complexes with higher activity antioxidants.

Quantum Chemistry Based Computational Study on the Conformational Population of a Neodymium Neodecanoate Complex

The title complex is widely used as an efficient key component of Ziegler-Natta catalyst for stereospecific polymerization of dienes to produce synthetic rubbers. However, the quantitative structure-activity relationship（QSAR） of this kind of complexes is still not clear mainly due to the difficulties to obtain their geometric molecular structures through laboratory experiments. An alternative solution is the quantum chemistry calculation in which the comformational population shall be determined. In this study, ten conformers of the title complex were obtained with the function of molecular dynamics conformational search in Gabedit 2.4.8, and their geometry optimization and thermodynamics calculation were made with a Sparkle/PM7 approach in MOPAC 2012. Their Gibbs free energies at 1 atm. and 298.15 K were calculated. Population of the conformers was further calculated out according to the theory of Boltzmann distribution, indicating that one of the ten conformers has a dominant population of 77.13%.

Reaction Activity of Kao linite Surfaces:Quantum Chemistry Calculations

The anion kaolinite surface interactions and AuS - adsorption onto the surfaces of kaolinite were studied using the self consistent field discrete variation (SCF-X α-DV) method.Electronic structure and energies of the system of anion AuS - adsorbed on an atomic cluster of kaolinite were calculated.The results show that the systems with lower total energy are those AuS - adsorbed on the edge surfaces,which indicates that the systems of adsorption of AuS - on the edges are more stable relative to those adsorbed on the basal plane.On the other hand,bond order data suggest that significant shifting of atomic charge and the overlapping of electronic cloud between Au (Ⅰ) of the AuS - and the surface ions of kaolinite would take place in the systems with AuS - being adsorbed on the edges,especially at the site near Al octahedra.Therefore,it can be concluded that edge sites will dominate the complexation reactions of the surfaces of kaolinite,with negligible contributions from other functional groups on the basal plane,which are dominated by either siloxane sites in silica layers or aluminol sites in gibbsite layers.

Quantum Chemistry Studies on the Free-radical Growth Mechanism of Polycyclic Arenes from Benzene Precursors

The free-radical growth mechanisms for the formation of polycyclic arenes (PCAs) were constructed based on the block unit of benzene, and were calculated by the quantum chemistry PM3 method. Two kinds of reaction paths are proposed and discussed. The calculation results show that the formation of PCAs is only controlled by the elimination of H atom from benzene, and the corresponding activation energy is 307.60 kJ·mol-1. H2 is only the ef-fluent gas in our proposed reaction mechanism, and the calculation results are in accord with the experimental facts.

The Application of SCC-DV-X_a Computational Method of Quantum Chemistry in Cement Chemistry

It has been explored why quantum chemistry is applied to the research field of cement chemistry. The fundamental theory of SCC-DV-Xα computational method of quantum chemistry is synopsized. The results obtained by computational quantum chemistry method in recent years of valence-bond structures and hydration activity of some cement clinker minerals, mechanical strength and stabilization, of some hydrates are summarized and evaluated. Finally the prospects of the future application of quantum chemistry to cement chemistry are depicted.

The Quantum Chemistry Calculation and Thermoelectricsof Bi-Sb-Te Series

The density junction theory and discrete variation method ( DFT - DVM) was used to study correlation between composition, structure, chemical bond, and property of thermoelectrics of Bi-Sb-Te series. 8 models of Bi20-xSbxTe32(x = 0,2,6,8,12,14,18 and 20) were calculated. The results show that there is less difference in the ionic bonds between Te( I)-Bi(Sb) and Te(Ⅱ)-Bi(Sb) , but the covalent bond of Te(Ⅰ)-Bi( Sb ) is stronger than that of Te(Ⅱ)-Bi( Sb ) . The interaction between Te(Ⅰ) and Te(Ⅰ) in different layers is the weakest and the interaction should be Van Der Wools power. The charge of Sb is lower than that of Bi, and the ionic bond of Te-Sb is weaker than that of Te-Bi. The covalent bond of Te-Sb is also weaker than that of Te-Bi. Therefore, the thermoelectric property may be imfiroved by adjusting the electrical conductivity and thermal conductivity through changing the composition in the compounds of Bi-Sb-Te. The calculated results are consistent with the experiments.

Quantum Chemistry Calculation on Oxygen and Nitrogen Adsorption in Carbon Nanotude

Oxygen and nitrogen adsorption in single walled carbon nanotube (SWCNT) is studied by density function and discrete variational (DFT-DVM) method.The models of O 2 and N 2 adsorption in the SWCNT are optimized based on the energy minimization.The calculated results of density of state,populations and energy gaps of the molecular orbitals show that oxygen adsorption in SWCNT increases the carbon nanotube`s electrical conductivity more notably than nitrogen adsorption,which is consistent with the experiment.

STUDIES OF QUANTUM CHEMISTRY CALCULATION ON VALENCE-BOND STRUCTURE AND HYDRATION ACTIVTY OF C_(12)A_7

The structure, chemical bonds and hydra-tion activity of C12A were studied by SCC-DV-Xa method of computational quantum chemistry. The calculated results show that Ca-O bond will be first broken off when C12A hydrates, the reactivity of Al(2)O4 tetrahedron is superior to that of Al(1)O4 tet, thedron and the rupture of the Al-O-Al chain composed of two types of AlO4 tetrahedra under the action of water lies in the very weak Al(2)-O(2) bonds. the Al-O bond strength of C12A7 is between C3A and C11A7·CaF2.

Structure and Quantum Chemistry Study on Hexaacetyl D-Mannose Hydrazine

Hexaacetyl D-mannose hydrazine is one type of important intermediates in saccharide chemistry. In this paper, its single crystal was obtained and furthermore, X-ray diffraction and quantum chemistry calculation were performed. It belongs to orthorhombic system, space group P212121, with a=16.267（3）, b=19.263（3）, c=7.1948（12）A, Mr=446.41, Dc=1.315 g/cm^3, V=2254.5（6）A^3 and Z=4. Meanwhile, the experimental results also provide information for designing a kind of molecular switch based on the mannose nitrogenous derivatives.

Mechanism studies of 5-HMF pyrolysis by quantum chemistry

The pyrolysis of 5-HMF was investigated using density functional theory methods at B3LYP/6-31 G++(d, p) level. Two possible pyrolytic pathways were proposed and full optimization of the energy gradient for the structures of reactants, products, intermediates and transition states of various reactions was implemented. The standard kinetic parameters in each reaction pathway were calculated and the formation and evolution mechanism of main pyrolysis products were analyzed. Bond dissociation energies calculation results show that the bond dissociation energy of CH_3—OH of 5-HMF is the lowest and the order of all kinds of bond dissociation energy is CH_3—OH<C—H<CH_3 OH—C_(aromatic)<CHO—C_(aromatic)<C_(aromatic)—H. In pathway(1), the energy barrier of furfural is 322.8 kJ/mol, the energy barrier of 2-furfuryl alcohol is 375.4 kJ/mol; the energy barrier of furan-2,5-dicarbaldehyde is 496.1 kJ/mol; the energy barrier of 5-methyl furfural is 375.8 kJ/mol, and the energy barrier of 2-methyl furan is 375.8 kJ/mol. In pathway(2), the activation energy required for open-loop with H_2O is higher.

Quantum Chemistry Studies on the Difference of Structures and Electronic Properties of Polyacene,Polypyridinopyridine and Paracyanogen

Polyacene (PAS), polypyridinopyridine (PPyPy) obtained by substitution of -N = for -CH = in PAS, and paracyanogen (Pc) molecules have been studied using quantum chemistry MNDO, 1D tight-binding CNDO/2-CD methods. The analyses of the energy band structures indicate that the substitution of N atoms changes the molecular structures and increases the activity points of electrophilic or nucleophilic doping, but intrinsical conductivity is not improved.