Noise-driven numerical irreversibility in molecular dynamics technique

It is widely believed that, in molecular dynamics (MD) simulations, round-off errors can cause numerical irreversibility since, in the standard MD, floating-point real number arithmetic is employed and round-off errors cannot be avoided. To investigate the characteristic of this numerical irreversibility, the 'bit-reversible algorithm', which is completely time-reversible and is free from any round-off error, is made use of as a test bed. Through this study, it is clearly demonstrated that, other than the extent of the stability of the system, the appearance of irreversibility is related to the 'quantity' of the controlled noise. By means of the bit-reversible simulation added to the controlled noise of an appropriate 'quantity', the characteristic of the numerical irreversibility in the standard MD is revealed.