Methane hydrates(MHs)play important roles in the fields of chemistry,energy,environ-mental sciences,etc.In this work,we em-ploy the generalized energy-based fragmenta-tion(GEBF)approach to compute the bind-ing energies and Raman spectra of various MH clusters.For the GEBF binding energies of var-ious MH clusters,we first evaluated the various functionals of density functional theory(DFT),and compared them with the results of explic-itly correlated combined coupled-cluster singles and doubles with noniterative triples correc-tions[CCSD(T)(F12*)]method.Our results show that the two best functionals are B3PW91-D3 and B97D,with mean absolute errors of only 0.27 and 0.47 kcal/mol,respectively.Then we employed GEBF-B3PW91-D3 to obtain the structures and Raman spectra of MH clusters with mono-and double-cages.Our results show that the B3PW91-D3 functional can well reproduce the experimental C-H stretching Raman spectra of methane in MH crystals,with errors less than 3 cm-1.As the size of the water cages increased,the C-H stretching Raman spectra exhibited a redshift,which is also in agreement with the experimental"loose cage-tight cage"model.In addition,the Raman spectra are only slightly affected by the neighboring environment(cages)of methane.The blueshifts of C-H stretching frequencies are no larger than 3 cm-1 for CH4 from monocages to doublecages.The Raman spectra of the MH clusters could be combined with the ex-perimental Raman spectra to investigate the structures of methane hydrates in the ocean bottom or in the interior of interstellar icy bodies.Based on the B3PW91-D3 or B97D functional and machine learning models,molecular dynamics simulations could be applied to the nucleation and growth mechanisms,and the phase transitions of methane hydrates.

Lei Zhang;Zheng Cheng;Wei Li;Shuhua Li

Key Laboratory of Mesoscopic Chemistry of Ministry of Education,Institute of Theoretical and Compu-tational Chemistry,School of Chemistry and Chemical Engineering,Nanjing University,Nanjing 210023,China

化学物理学报（英文版）

[1]Lei Zhang;Zheng Cheng;Wei Li;Shuhua Li-.Generalized Energy-Based Fragmentation Approach for Accurate Binding Energies and Raman Spectra of Methane Hydrate Clusters)[J].化学物理学报（英文版）,2022(01):167-176

MHs,ploy,GEBF,explic,itly,noniterative,B97D,blueshifts,monocages,doublecages

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