CONCENTRATED, SEMIFLEXIBLE LATTICE CHAIN SYSTEMS AND CRITICISM OF THESCANNING TECHNIQUE

The thermodynamics of concentrated, semiflexible lattice chain systems are determined by computer simulation. An order-disorder transition i s observed in both two and three dimensions. In two dimensions the tra nsition is second-order and critical. In three dimensions it is first- order. The entropy is obtained as a function of temperature with suffi cient accuracy to test the scanning technique, a procedure devised to simulate the entropy of lattice chains. The scanning procedure cannot approximate the entropy of the systems considered here. Scanning is un reliable whenever interactions occur between parts of the system const ructed at widely different times. Unfortunately, this includes all sys tems to which it is now being routinely applied. The problem is most s evere in concentrated multiple chain systems and less so in isolated s elf-avoiding walks.