| Hydrogen bond(O-H···O),which exists in liquid,crystal and some other systems widespreadly,it exhibits the gentle but complex intermolecular interaction in hydrogen-bonded systems.The hydrogen bonds in the water can affect many structures of biological substance's properties such as protein,DNA.There are also other peculiar phenomena as anomalous expansion of water is also related to hydrogen bonds,which attracts the researchers in different fields to explore the mystery of water and obtained many achievements.For example,the cooperative effect of hydrogen bond was established in the middle of last century,which shows the O-H bond length,and the bond energy of H-bond(H···O)increases with the decreases of intermolecular distance.Besides water,it exists in hydrogen-bonded systems widely and affects the geometry,energy,vibration as well as the arrangement of monomers in the molecules.For the theoretical approaches applied on hydrogen-bonded systems at the atomic level,there are ab initio,density function theory(DFT),tight-binding density function theory(DFTB)as the representative method of semiempirical approaches,force field(FF)methods.It indicates that the theoretical study of hydrogen bond has been contained in all theoretical methods at atomic level,and there are abundant theoretical tools can be used for describing and explaining the phenomena of hydrogen bond.In our work,we mainly study the properties of hydrogen bond in water system with coupled-cluster singles and doubles with perturbative triple excitations(CCSD(T))method,we find the opposite change trend of bond length and energy with CCSD(T)method,which can be seen as the uncooperative effect of hydrogen bond.The finding can be further explained from perspective of electron correlation.Most importantly,by comparing the geometry obtained in methods of DFT and CCSD(T),we adjust the parameters in DFT method and further analysis the properties of molecular interaction in complex systems.The researches in the paper uncovered the macroeconomic effect of electronic correction in the intermolecular interaction especially the hydrogen bond in water system,it also promotes the development of parameterized theoretical methods.Firstly,we investigated the water dimer with ab initio CCSD(T)and other diverse methods including DFT,force field methods as well as DFTB method with different dispersion,and obtained the nature of the structure and bond energy with the decrease of intermolecular distance.With the intermolecular distance in the stable structure reduces in the range of 0.24 (?),we find that the O-H bond length decreases and H-bond(H···O)is weaker with coupled-cluster singles and doubles with perturbative triple excitations)CCSD(T))method,even with explicitly correlated coupled-cluster singles and doubles with perturbative triple excitations)CCSD(T)-F12)methods.It is opposite with the cooperative effect of hydrogen bond raised in the middle of last century,which can be seen as the uncooperative effect of hydrogen bond.The finding can be explained by the exchange repulsion of electrons decomposed in energy decomposition based on the high-level Symmetry-Adapted Perturbation Theory,and can be attributed to the Coulomb dynamic correction of electrons considered in the ab initio CCSD(T)method that the electrons with opposite spin can't occupy the same position,which is contained in the exchange repulsion term.With the decrease of intermolecular distance,the percentage of exchange repulsion of electrons increases and dominates the interaction of monomers.The existence of uncooperative effect of hydrogen bond in water dimer prevents more hydrogen bonds connecting other molecules to be formed,which can explain the stable existence of water dimer in vapor phase.Besides,it provides reference for the develop of DFT methods and other diverse approaches and it is beneficial for opening the researches field of electron correlation on geometry of hydrogen-bonded system.Secondly,we further researched the small water clusters,comparing the stable structure of water trimer and water tetramer with ab initio CCSD(T)method,we observed the cooperative effect of hydrogen bond,with the increase of water monomers' numbers,the O-H bond length and H-bond(H···O)energy increase with decrease of intermolecular distance and H-bond(H···O)bond length.While with the O···O distance decrease in the stable structure of water trimer,tetramer,pentamer,hexamer respectively,we find the transfer process of the uncooperative effect of hydrogen bond to cooperative effect of hydrogen bond with the increase of water monomers.The O-H bond length increase first but decrease later in water trimer,while in the tetramer,the O-H bond length increase continually.For the pentamer and hexamer,the change trend of O-H bond length is consistent with the tetramer.Besides the change of geometry,the decreasing bond energy of H-bond(H···O)in the water trimer changes to increase in the tetramer.It can conclude that the(H2O)n(n=3,4)can be seen as the transition region of the uncooperative to cooperative effect of hydrogen bond in water system.The transfer process of uncooperative effect of hydrogen bond can be explained by the electrostatic interaction between the non-adjacent water monomers added in the water tetramer,the value and percentage in the total interaction is much larger than the electrostatic interaction between adjacent water monomers in the trimer.It can account for the different change trend of geometry and energy in two sides of transition region.It makes a deeper understanding of cooperative effect's boundary in hydrogen bond of water from quantum perspective.Thirdly,considering the compute with CCSD(T)method consumes large resources,the complex systems are difficult to be computed with CCSD(T)method,it is necessary to develop the adjusting parameters in DFT methods based on first-principles.By adjusting the parameters of DFT,reducing the value and percentage of the Hartree-Fock(HF)exchange term in the B3LYP,we found the repulsion interaction is enhanced between monomers in the water dimer.The regular of geometry with parameter obtained in B3LYP is applied on wB97X.Because of there is long-range exchange term further considered in wB97X,the geometry and energy of water dimer applied with wB97X were close to the corresponding results of CCSD(T)with the value of HF exchange term reduced to 0.4.Besides,the parameter-adjusted wB97X is performed in the scanning of hydrogen bond connecting base-pairs(A-T,C-G)in DNA,we find that the reduction of HF exchange term doesn't change the cooperative effect of hydrogen bond,which shows the difference of hydrogen bond between base-pairs in DNA and water system at atomic level and consistent with the recognition of DNA in the past.The wB97X with parameters adjusted is also applied on theoretical study of the nanotubes adsorbed with small molecules.The adsorption energy and charge transfer obtained by wB97X with parameters adjusted is consistent with other DFT as well as DFTB methods.It shows that the ad-atom and vacant defective nanotubes adsorbed with NH3 is chemical adsorption,which is accompanied with large charge transfer and adsorption energy.Besides,we find that the value of the HF exchange term is reduced,the intermolecular distance in the stable structure of chemical adsorption is increased,it indicates the repulsion effect is enhanced,demonstrating the parameters adjusted in DFT method is not only appropriate for studying the process of complex systems' compression,but also can be applied for the researches about defective nanotubes adsorbed with small molecules.By the systematic study,the uncooperative effect of hydrogen bond is found.We further investigate the transfer process of uncooperative to cooperative effect in the water system.Besides,the adjusted parameters in the DFT method achieves the same change trend of geometry and energy with CCSD(T)method in the compression of water,which also shows applicability in base-pairs in DNA and adsorption of small molecules on defective nanotubes.The researches of the paper can be the important puzzle for understanding the mechanism of hydrogen bond,promoting the research progress for electron correlation on complex intermolecular interaction. |
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