CAJ | 학술논문

采用分子动力学方法对液态金属钠的凝固过程进行了模拟计算，运用团簇结构表征新方法――团簇类型指数法（ CTIM）对凝固过程中的团簇结构进行了识别。为了阐明CTIM在识别团簇结构上的准确性和效率，将其与广为采用的Voronoi 多面体方法（ VPM）进行比较。结果表明：当采用CTIM 和VPM分别对液态金属钠凝固结构中的原子团簇结构进行表征时，它们所得到的微观结构特征是一致的。非晶态结构中，原子团簇类型的分布呈现明显的区段特征，每一区段都存在一种主要团簇类型，它们分别是二十面体或其缺陷结构。晶体结构中，体系形成以BCC团簇为主体的晶态结构。同时发现， VPM不易区分不同团簇构型之间的细微差别，不同构型的原子团簇可能被归为同种结构类型；而CTIM根据近邻原子之间相对位置关系，直接准确描述原子团簇的构型。不但由CTIM分析获得的凝固体系结构特征与VPM的分析结果一致；而且CTIM抓住了体系微观结构特征的主要方面，简化了团簇结构的表征形式，这在大尺度模拟体系的结构分析中将具有较高效率。
채용분자동역학방법대액태금속납적응고과정진행료모의계산，운용단족결구표정신방법――단족류형지수법（ CTIM）대응고과정중적단족결구진행료식별。위료천명CTIM재식별단족결구상적준학성화효솔，장기여엄위채용적Voronoi 다면체방법（ VPM）진행비교。결과표명：당채용CTIM 화VPM분별대액태금속납응고결구중적원자단족결구진행표정시，타문소득도적미관결구특정시일치적。비정태결구중，원자단족류형적분포정현명현적구단특정，매일구단도존재일충주요단족류형，타문분별시이십면체혹기결함결구。정체결구중，체계형성이BCC단족위주체적정태결구。동시발현， VPM불역구분불동단족구형지간적세미차별，불동구형적원자단족가능피귀위동충결구류형；이CTIM근거근린원자지간상대위치관계，직접준학묘술원자단족적구형。불단유CTIM분석획득적응고체계결구특정여VPM적분석결과일치；이차CTIM조주료체계미관결구특정적주요방면，간화료단족결구적표정형식，저재대척도모의체계적결구분석중장구유교고효솔。
A molecular dynamics simulation has been performed on the solidification process of liquid Na , and the atomic clusters in the solidification process have been identified by means of a new characterization method --cluster-type index method ( CTIM) proposed by us .In order to evaluate the reliability and efficiency of CTIM , it is compared with the widely used Voronoi polyhedron method (VPM).Our results show that when the atomic clusters in the solidification structures of liquid Na are characterized by the VPM and CTIM , respectively , their structural features are identical .The distributions of atomic clusters in the amorphous structure characterized by the two different methods both display several broad peaks , and each peak corresponds to one favorable cluster type .The favorable cluster types both are icosahedron and its defective cases .The dominated cluster type in the crystal structure characterized by the two different methods both is bcc crystal unit .It is also found that the VPM is difficult to distinguish the small differences between cluster configurations according to the shapes of Voronoi polyhedra , and different cluster configurations may be classified into the same type .The CTIM directly describes cluster configurations according to the position relations of neighbor atoms .CTIM simplifies the representation format of atomic clusters by means of outstanding the principal ones .This will be efficient in the structural analy-sis of larger-scale simulation systems .