Theoretical Studies On Vibration And Electronic Structure In Intermolecular Systems

Intermolecular interaction is an important origin of the variety in nature world.It constructs the relatively flat but complex intermolecular potential energy surface(PES)that allows complexes to express molecular-level flexibility,holds the delicate balance among monomers and implements various cooperation among different molecules.Correspondingly,the matter transportation,energy transfer and phase transition could emerge as well as the life processes under mild environments.On the other hand,its relatively weak interaction strength permits sensitive responses to monomeric morphology,electronic structure and external physical and chemical conditions,thus provides paths towards manipulation on microscopic world.However,the side effect of above flexibility and sensitivity brings challenge to comprehensive understanding on the intermolecular behavior.On one hand,as the intrinsic nature of all physical systems,the occurrence of vibration in intermolecular freedom inclines to move nuclei with relatively large spatial amplitude due to the flatness of PES,thus may remarkably change the key factors like intermolecular distance and complex conformation then induce corresponding non-equilibrium evolution of electronic structure.This suggests the corresponding physical nature maybe beyond the capability of conventional static models.On the other hand,the pursuit towards atomic-level operability and bottom-up construction of nanostructures urges the design and manufacture of monomers with novel electronic structures.However,as one of the key characteristics that can probe the structure of corresponding assemblies,the response of intermolecular vibrations to the emerging freedom of intermolecular coupling between monomeric electronic structures still needs systematic investigations.In this work,aiming at above two problems that are of both fundamental significance and application potentials,first-principles methods with electronic-structure analysis in the dynamic angle are conducted to explore two topics.Respectively,they are dependence of characteristic interlayer vibrations to interlayer spin arrangements in typical small-sized stacked graphene nanofragments and the dynamic effect of intrinsic zero-point vibration to the elementary H-bond in a ground-state water dimer.Stacking is one of the key effects to be relied on in bottom-up assembling and device design based on nanostructure building-blocks.The freedom of interlayer spin coupling could emerge when assembling small-sized graphene-based nanostructures through stacking.Its possible influence on interlayer vibrations could be significant for developing Raman probes towards small complexes and device design involving intermolecular vibronic process.In this paper,using density-functional-theory calculations on bilayer and trilayer rhombic graphene fragments,finite-size analogues to interlayer shear and breathing modes are compared regarding to ferromagnetic and antiferromagnetic interlayer spin arrangements.For bilayer units,the antiferromagnetic configuration further separates two shear mode components by around 10 cm-1,inducing a Raman peak splitting.This response is robust regarding to slightly enlarging the fragment and increasing layer number to three.Layer breathing mode is spin-arrangement robust in bilayers but show different arrangement-sensitivity in ABA-like and ABC-like trilayers.Visualization of interface electron density reveals the dependence of anisotropic interface environment to interlayer spin arrangement and unambiguously correlates the arrangement style with shearing responses.Further application of this analysis clarifies the arrangement-based phase-cooperation in trilayer shearing.Results and analysis in this work may contribute to the characterization and design of graphene-based nanostructures as well as understanding the interfacial nature beneath their intermolecular varieties in dynamic processes.Among various kinds of intermolecular interactions,hydrogen bonding(H-bonding)facilitates those gentle but sophisticated phenomena in H-bond networks diversely presenting in solvation,crystal,interface and organic complexes.Secondly,within quasi-classical frame,we try providing mode-specific intuitive interpretation of ZPV dynamic effects on an elementary H-bond in water dimer.Current theoretical architecture shaping the dynamic template of elementary H-bond sits on an infirm quasi-classical base,where temporal-spatial fluctuations from the intrinsic zero-point vibration(ZPV)have scarce mode-specific resolution in fundamental dimensions of geometry,electronic-structure and interaction energy.Here,based on ab initio molecular dynamics simulation of a ground-state water dimer,temporally separated fluctuation features as the long-time weakening and the minor short-time strengthening are respectively assigned to two low-frequency intermolecular ZPV modes and two O-H stretching ones,with the geometric effect of former modes instantaneously lengthening H-bond up to 0.19 ?.Moreover,accompanied electronic-structure fluctuation crosses criteria borders dividing partially covalent and noncovalent H-bonding established for equilibrium models,as indicated by electron density and electron energy density at H-bonding critical points.Meanwhile,as results from the simultaneous fluctuation of all geometric freedoms under the guidance of ZPV in 12 normal modes,the evolution of interaction energy and corresponding decomposed terms with respect to fundamental parameters like H-bond length is qualitatively distinct from conventional experiences from quasi-static dragging models,which even breaks the “U” shape profile conventionally anchored at the equilibrium state.Further assignment of electronic-structure and energy fluctuation to contributions from all modes reclaims the importance of those two intermolecular modes in implementing the intrinsic dynamic behavior.Extended quasi-classical understandings on ground-state water dimer further approach the dynamic nature of H-bond meanwhile support upper-building explorations towards ultrafast and mode-specific manipulation as well as interpretations involving intuition from normal-mode disclosure.Through above atomic-level researches,in typical intermolecular scenario as stacking and H-bonding,we respectively and preliminarily investigated the influence of intermolecular electronic-structure coupling on nuclei vibrations and the reversed electronic-structure evolution driven by intrinsic zero-point nuclei motions.Through the intercourse between dynamic behaviors of nuclei and electronic structure in vibration processes,we glanced at the beauty of dynamic nature of intermolecular interaction.The view angle and study experiences is expected to inspire researchers to further pursuit the figure of intermolecular interaction and we wish the specific regulations obtain in our journey to promote technology advance in device design based on stacked nanostructure and ultrafast manipulation of H-bonded systems.