The structural transformation and reburning characteristics of gas coal in Ningwu coalfield fire

With the expansion of the scale of coal mining, the safety problems caused by the reburning of coal are becoming more and more serious. In this paper, the pyrolysis characteristics of gas coal and the exothermic characteristics of reoxidation of residues were studied by using a synchronous thermal analyzer. The functional groups of pyrolysis residues were tested, and the group content and characteristic structural parameters were calculated based on quantum chemistry method. The results show that with the increase of pyrolysis temperature, Volatile maximum separation rate (Vmax) and the change in the residual weight of the coal sample (ΔWvp) increase. The increase of temperature will lead to the decrease of hydroxyl and aliphatic hydrocarbon content in coal, and the increase of aromatic hydrocarbon. With the deepening of pyrolysis, the ignition point temperature of coal samples decreases first and then rises, the combustion intensity and combustion concentration are strengthened. The pyrolysis results show that 462.8°C is the critical temperature for the transition during pyrolysis. The ignition point of the residue is less affected by the pyrolysis conditions, and the ignition temperature of the raw coal and the pyrolysis residue varies within 330.57°C–334.98°C.

Exploration of Chemical Compound, Conformer, and Reaction Space with Meta-Dynamics Simulations Based on Tight-Binding Quantum Chemical Calculations

The semi-empirical tight-binding based quantum chemistry method GFN2-xTB is used in the framework of meta-dynamics (MTD) to globally explore chemical compound, conformer, and reaction space. The approach us used for three common problems, i.e., conformer search, chemical reaction space exploration in a virtual nanoreactor, and for guessing reaction paths. <div>For typical conformational search problems of drug-like organic molecules, the new MTD(RMSD) algorithm yields lower energy structures and more complete conformer ensembles at reduced computational effort compared with its already well performing predecessor.<br><br></div>

Exploration of Chemical Compound, Conformer, and Reaction Space with Meta-Dynamics Simulations Based on Tight-Binding Quantum Chemical Calculations

The semi-empirical tight-binding based quantum chemistry method GFN2-xTB is used in the framework of meta-dynamics (MTD) to globally explore chemical compound, conformer, and reaction space. The approach us used for three common problems, i.e., conformer search, chemical reaction space exploration in a virtual nanoreactor, and for guessing reaction paths. <div>For typical conformational search problems of drug-like organic molecules, the new MTD(RMSD) algorithm yields lower energy structures and more complete conformer ensembles at reduced computational effort compared with its already well performing predecessor.<br><br></div>

Double-helix PnLin chains: novel potential nonlinear optical materials

The structures, circular dichroism (CD) spectra and nonlinear optical (NLO) responses of a series of inorganic double-helix chains, PnLin (n = 6–12), have been investigated using the quantum chemistry method.

Exploring what prompts ITIC to become a superior acceptor in organic solar cell by combining molecular dynamics simulation with quantum chemistry calculation

A comparison on charge transfer process in OSC between non-fullerene electron acceptor ITIC and PC71BM was taken by microscopic analysis based on the molecular dynamics and quantum chemistry method.

Abnormally high oscillator strengths of the graphene nanoribbons electronic spectrum: quantum chemistry calculations

Armchair-edged narrow graphene nanoribbons (GNRs) are modelled by semi-empirical Hartree–Fock based quantum chemistry method ZINDO/S-CI. ​Abnormally high oscillator strengths of over 200 are found in long GNRs (length > 150 hexagonal carbon rings).

The effect of nitrido, azide, and nitrosyl ligands on magnetization densities and magnetic properties of iridium PNP pincer-type complexes

The magnetisation density of different iridium PNP pincer-type complexes depends on the chosen quantum chemistry method.

Crystal, molecular and electron structure of (2R,3R,4aS,5S,7R,10aS,10bS)-5-ethyl- 2,3-dimethoxy-2,3,7-trimethyl-decahydro-2H- [1,4]dioxino[2,3-g]indolizin-7-ium iodide hydrate

The title compound, C17H32NO4I・H2O, is chiral molecule with seven stereogenic centres. The absolute configuration was assigned from the synthesis and confirmed by the structure determination. The central six-membered ring of the indolizine moiety and 1,4-dioxane ring adopt a chair conformation, with two atoms displaced by -0.530(3), 0.712(3) and -0.631(2), 0.602(2) Å, respectively, from the plane of the other four atoms. The conformation of the pyrrolidine ring is close to that of a envelope, with the flap atom displaced by -0.600(3) A from the plane through the remaining four atoms. The electron structure was calculated by the semiempirical quantum chemistry method PM3. The crystal structure of compound is stabilized by O-H・・・I and O-H・・・O hydrogen bonds.