关键词: 力常数, 一般价力场, M(CSe(NH₂)₂)₄²⁺ (M=Pd(Ⅱ), Pt(Ⅱ))

Abstract: At first, the method for defining the force constants of GVFFfrom that of UBFFhas been set up in this paper.Through a serial transforms,we can conveniently obtain F_s force constants matrix in symmetric coordinates in UBFF. According to the idea that in the local symmetry force field there is the . transferability of force constants related to different functional groups in the molecules having similar structure, and we transfer the F_S matrix from UBFFto GVFFfor the same molecule, that is: (F_S)_GVFF = (F_S)_UBFF. Then the (F_S)_GVFF is transformed by the-converse transform of the Umatrix to the Fr in GVFF, which--is used as the initial force constant F° in Wilson's equation. In this paper, we still further study the method of kinematically defined fore constants. This method starts from the determination of force constants by the factorization of Gmatrix and vibrational frequencies. Yan Guosin etc. have discussed the., problem of- the-ordering of eigenvalues λ_i in Λ matrix. The advance- here for it has made in the two respects; in the using, the higher dimensional matrix F_S has- calculated, by an above rule, and the dimension of symmetry species have expanded to 16.In the method,we give a solution on the new problem that two frequencies belong tothe same symmetric coordinates, if frequencies v_i and v_i belong to S_i and S_i, while v_k and v_l to S_k and S_l,the four possible orderings were considered and the correspond force constants were calculated by those orderings respectively. It had been shown that in Born-Oppenheimer approximation the force constants of the molecule due to isotopic substitution are invariable, then, we calculate .the vibration-al frequencies of the isotopic molecule with the several set of force condtants given above and compare them with the observed isotopic frequencies respectively. The ordering in which the frequency error is smallest would be choosed. The normal vibrational analyses of the molecules M(NH₂CSeNH₂)₄²⁺, {M = Pd(Ⅱ), Pt(Ⅱ)} are carried out by the above methods.

Key words: force constant, GVFF, M(NH₂CSeNH₂)₄²⁺{M = Pd(Ⅱ),Pt(Ⅱ)}