Correlation regimes in systems of soft spherical particles studied by their Lyapunov exponents

We performed molecular dynamics simulations of soft spherical particles over wide ranges of densities and temperatures corresponding to fluids, glasses and crystalline solids, and calculated the full Lyapunov spectra of these systems. For either phase corresponding exponents essentially scale with the square-root of the temperature in accordance with kinetic theory. The density dependence is more pronounced and less systematic. The shape of the spectrum of a glass is different from that of a crystalline solid at the same density and temperature and resembles the spectrum of the initial dense liquid-like phase. For dilute gases the sum of the positive exponents approaches zero and is increasingly dominated by the largest exponent. Although systematic changes of the Lyapunov spectra were observed, it seems that the spectral shape does not uniquely determine the phase of the system.