Simulational analysis of glasses prepared via different interatomic potentials

All glasses and amorphous solids have common characteristics; That is to say, they have no long-range order (LRO), but maintain the short-range order (SRO) reflecting the types of cohesion. In order to classify glasses beyond this common feature, therefore, it is necessary to introduce some other measure by which we can distinguish different atomic structures of glasses. Under this situation, it is the purpose of the present article to propose such a quantity. To this end, we first carry out, by means of molecular-dynamics (MD) method, rapid-quench simulations to construct glassy structures of the Lennard-Jones (LJ) systems and of the systems with the Stillinger-Weber (SW) potentials. Secondly, we evaluate several physical properties of the glasses thus obtained. Note that the crystalline phase of an LJ system is fcc which is the closest-packing structure, while that of an SW system is bcc where the atoms are more sparsed than in fcc. Among several quantities we calculate, we pay special attention to the pair-distribution function g(r), r being the interatomic distance, the bond orientational parameter W 6 , and the frequency spectrum F(ω),ω being the vibrational frequency. The behavior of g(r) confirms the absence of the LRO. On the other hand, the behaviors of W6 for the nearest-neighbor atoms show the existence of the SRO in the form that the nearest-neighbor configurations are icosahedral as expected for these glasses. Interesting results are found in F(ω) in the sense that, in some glasses, the peaks appear in F(ω) at almost the same to at the peak position in the case of an fcc crystal. From the analyses of W6 for atoms in the second-neighbor shell of each central atom, we find that the origin of the peaks in F(ω) comes from the cubic-like configurations of the atoms in the second-neighbor shell. We discuss this problem in detail and propose that F(ω), which is a macroscopically-observable quantity, is used as a measure to detect the degree of the IRO.