MM CALCULATIONS OF THE METAL-PROTEIN MODEL COMPLEXES Ⅰ.MOLECULAR FORCE FIELD FOR COBALT COMPEXES

Cobalt-protein complexes play an important role in biochemical processes.The structure of the model molecule,Co(H_2O)_3SO_4(phen) has been studied by molecular mechanics.The molecular force field (MM2) parameters have been developed for the particular class of the complexes.

Molecular simulation studies of hydrocarbon and carbon dioxide adsorption on coal

Sorption isotherms of hydrocarbon and carbon dioxide （CO2） provide crucial information for designing processes to sequester CO2 and recover natural gas from unmineable coal beds. Methane （CH4）, ethane （C2H6）, and CO2 adsorption isotherms on dry coal and the temperature effect on their maximum sorption capacity have been studied by performing combined Monte Carlo （MC） and molecular dynamics （MD） simulations at temperatures of 308 and 370 K （35 and 97 ~C） and at pressures up to 10 MPa. Simulation results demonstrate that absolute sorption （expressed as a mass basis） divided by bulk gas density has negligible temperature effect on CH4, C2H6, and CO2 sorption on dry coal when pressure is over 6 MPa. CO2 is more closely packed due to stronger interaction with coal and the stronger interaction between CO2 mole- cules compared, respectively, with the interactions between hydrocarbons and coal and between hydrocarbons. The results of this work suggest that the ＂a＂ constant （pro- portional to TcPc） in the Peng-Robinson equation of state is an important factor affecting the sorption behavior of hydrocarbons. CO2 injection pressures of lower than 8 MPa may be desirable for CH4 recovery and CO2 sequestration. This study provides a quantitative under- standing of the effects of temperature on coal sorptioncapacity for CH4, C2H6, and CO2 from a microscopic perspective.

Microscopic mechanism study and process optimization of dimethyl carbonate production coupled biomass chemical looping gasification system

Biomass chemical looping gasification technology is one of the essential ways to utilize abundant biomass resources.At the same time,dimethyl carbonate can replace phosgene as an environmentfriendly organic material for the synthesis of polycarbonate.In this paper,a novel system coupling biomass chemical looping gasification with dimethyl carbonate synthesis with methanol as an intermediate is designed through microscopic mechanism analysis and process optimization.Firstly,reactive force field molecular dynamics simulation is performed to explore the reaction mechanism of biomass chemical looping gasification to determine the optimal gasification temperature range.Secondly,steady-state simulations of the process based on molecular dynamics simulation results are carried out to investigate the effects of temperature,steam to biomass ratio,and oxygen carrier to biomass ratio on the syngas yield and compositions.In addition,the main energy indicators of biomass chemical looping gasification process including lower heating value and cold gas efficiency are analyzed based on the above optimum parameters.Then,two synthesis stages are simulated and optimized with the following results obtained:the optimal temperature and pressure of methanol synthesis stage are 150℃ and 4 MPa;the optimal temperature and pressure of dimethyl carbonate synthesis stage are 140℃ and 0.3 MPa.Finally,the pre-separation-extraction-decantation process separates the mixture of dimethyl carbonate and methanol generated in the synthesis stage with 99.11%purity of dimethyl carbonate.Above results verify the feasibility of producing dimethyl carbonate from the perspective of multi-scale simulation and realize the multi-level utilization of biomass resources.

Atomistic understanding of rough surface on the interfacial friction behavior during the chemical mechanical polishing process of diamond

The roughness of the contact surface exerts a vital role in rubbing.It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level.Herein,the rough surface with a special root mean square(RMS)value is constructed by multivariate Weierstrass–Mandelbrot(W–M)function and the rubbing process during that the chemical mechanical polishing(CMP)process of diamond is mimicked utilizing the reactive force field molecular dynamics(ReaxFF MD)simulation.It is found that the contact area A/A0 is positively related with the load,and the friction force F depends on the number of interfacial bridge bonds.Increasing the surface roughness will increase the friction force and friction coefficient.The model with low roughness and high lubrication has less friction force,and the presence of polishing liquid molecules can decrease the friction force and friction coefficient.The RMS value and the degree of damage show a functional relationship with the applied load and lubrication,i.e.,the RMS value decreases more under larger load and higher lubrication,and the diamond substrate occurs severer damage under larger load and lower lubrication.This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.

Impact of lithium nitrate additives on the solid electrolyte interphase in lithium metal batteries

Lithium metal batteries(LMBs)represent a promising frontier in energy storage technology,offering high energy density but facing significant challenges.In this work,we address the critical challenge of lithium dendrite for-mation in LMBs,a key barrier to their efficiency and safety.Focusing on the potential of electrolyte additives,specifically lithium nitrate,to inhibit dendritic growth,we employ advanced multi-scale simulation techniques to explore the formation and properties of the solid electrolyte interphase(SEI)on the anode surface.Our study introduces a novel hybrid simulation methodology,HAIR(Hybrid ab initio and Reactive force field Molecular Dynamics),which combines ab initio molecular dynamics(AIMD)and reactive force field molecular dynamics(RMD).This approach allows for a more precise and reliable examination of the interaction mechanisms of nitrate additives within LMBs.Our findings demonstrate that lithium nitrate contributes to the formation of a stable and fast ionic conductor interface,effectively suppressing dendrite growth.These insights not only advance our un-derstanding of dendrite formation and mitigation strategies in lithium metal batteries,but also highlight the efficacy of HAIR as a pioneering tool for simulating complex chemical interactions in battery materials,offering significant implications for the broader field of energy storage technology.

3D-QSAR Studies on the Imidazopyrimidine Derivatives

Comparative molecular field analysis(CoMFA) and comparative molecular similarity indices analysis(CoMSIA) for imidazopyrimidine derivatives were performed to get the molecular active conformation selection, molecular alignment, as well as the establishment of corresponding 3 D-QSAR model. The model established by this method has good ability to predict such compounds. For CoMFA model, the cross-validated q2 and non-cross-validated r2 values are 0.665 and 0.872, respectively. The best q2 value for CoMSIA model is 0.632 and r2 value is 0.923. Using this information and the three-dimensional equipotential map for molecular design can theoretically obtain some new antibacterial drugs with higher activity. There are two newly designed molecules with activity values of 7.921 and 7.872, which are higher than that of the template molecule No. 12 with an activity value of 7.850, and the QSAR research results can provide a theoretical reference for the synthesis of new drugs.