1996Crystallisation and glass formation in liquid lead a molecular.pdfVIP

ELSEVIER Computer Physics Communications 97 (1996) 185-190 Computer Physics Communications Crystallisation and glass formation in liquid lead: a molecular dynamics study J. Rybicki 1, R. Laskowski l, S. Feliziani lstituto di Matematica e Fisica, Universita di Camerino, Italy Abstract The molecular dynamics (MD) simulations of crystallisation and glass formation in liquid lead have been performed. Two series of calculations are presented. 1. Isochoric quenches down to 1 K of liquid densified and rarefied lead at various cooling rates; 2. Isothermal (at 600K) compression and decompression at various compression rates. The resulting structures at 1K are analysed within the stochastic geometry methods. The changes of the potential energy, and of the diffusion coefficient during the pressure induced solidification are discussed. 1. Introduction We present the preliminary results of the molecu- lar dynamics (MD) simulation of crystallisation and glass formation processes in liquid lead (Pb). The simulations were performed in the microcanonical (NVT) and in the isoenthalpic-isobaric (NpH) en- sembles [1], using an experimental pair interaction potential [2,5], obtained by careful fitting of the MD results to the static structure factor S(k) at 623 K (23 K above the melting temperature). The interaction potential contains hard-core and soft-core repulsion terms and an oscillatory long-range Friedel compo- nent: V ( r ) = Vl(r) + V2(r) + V3(r) , Vl(r ) a , ( b J r ) 12 e x p [ ( r - c l ) - l], =- r c l , V l ( r ) - - 0 , r_c l, V 2 ( r ) = a 2 ( b 2 / r - c 2 ) e x p [ ( r - b 2 ) - ] , r b 2 , V2(r)=O, r ~ b 2, l Permanent address: Faculty of Technical Physics and Applied Mathematics, Technical University of Gdafisk, 80-952 Gdafisk, Poland. V3(r ) = a3 r-3 cos (2KFr ) , with the following, parameter values: a I = 102.5 meV, b 1=3.284 A, c 1=5.72 ,~, a 2 = 9 0 meV, * 03 b 2 = 4.83 A, c 2 = 0.5, a 3 =-418.3 meV A , K