TRIPLET CORRELATION-FUNCTIONS FOR HARD-SPHERES - COMPUTER-SIMULATION RESULTS

We present results for the triplet distribution function g(3)(r,s,t) o f hard-spheres obtained in extensive molecular-dynamics simulations; t he packing fractions we have investigated range from 0. 15 to 0.45. Th e simulation data have been compared to results for g(3) (r,s,t) which we calculated via some recently proposed analytical and numerical met hods; two of these methods are based on density-functional theory and the Wertheim-Thiele solution of the Percus-Yevick equation; another me thod, proposed by Barrat, Hansen, and Pastore uses a factorization ans atz for the pair direct correlation function and the last approximatio n is based on a formal density expansion of g(3) (r,s,t), truncated af ter second order. Furthermore we compared, simulation results to data obtained by the ''source-particle method'' (or PY3 method) proposed a few years ago by Attard. Attard's method shows an extremely good agree ment not only for general configurations, but in particular for partic les at direct contact; this approximation has to be considered as the most reliable method available for the numerical determination of the triplet-structure of a simple liquid. Concerning the results of the ot her methods discrepancies with the simulation data are observed in par ticular near the contact and for very close triplet-configurations. Ap art from Attard's approximation the second order density expansion giv es the best agreement. For less close configurations, i.e., if particl es are separated by 1.5 to 2 hard-sphere diameters, the results of all the methods investigated practically coincide.