A PRACTICAL METHOD TO AVOID POLYMER CHAIN BOND-CROSSING IN TWO DIMENSIONAL DISSIPATIVE PARTICLE DYNAMICS SIMULATIONS

摘要

@@Dissipative particle dynamics (DPD) simulation technique is a novel and effective method targeted on mesoscopic simulations, in which the interactions between particles are soft 1. As a result, it inevitably causes cross among different bonds and overlap between different particles. Here we develop a practical method based on the DPD model, which can reasonably avoid unphysical bond-crossing problem. In this method, we add a hard core to each particle by modifying the form of the conservative force in DPD so that the particles cannot overlap with each other. A preset maximum force with value Fmax is added to the conservative force when the distance between two particles are small enough, which is to insure that every DPD particle has a hard core which is impenetrable. Figure 1 shows the modified conservative force. When the distance between a pair of particles rif is less than the preset hard core diameter 2r0, both of the two particles will suffer the maximum force Fmax. The radial distribution function (RDF) is then used to check the actual value of the hard core radius, which is further used for fine tuning the hard core size. We refer to the simple geometry constraint conditions in three dimensions (Figure 2) and in two dimensions (Figure 3), respectively, to design the condition of bond uncrossibility in polymer chains.