Molecular dynamics of polymers with explicit but frozen hydrogens

A new form of holonomic constraint, called a conic constraint, is introduced for the purpose of eliminating the fast vibrations of hydrogen atoms in molecular simulations of systems of aliphatic chains. It can easily be combined with bond constraints in SHAKE/RATTLE algorithms for which a unified tolerance criterion is defined. The new form of constraint allows the use of rather large time steps (in the 2–3 fs range). The procedure is illustrated for a full atomic model of polypropylene.