# KINETIC=n.nnn

In a DRC calculation n.nnn kcal/mol of excess kinetic energy is added to the system.  At the start of a DRC calculation, the atoms are initially at rest.  So kinetic energy cannot be added to the system.  When KINETIC=n.nn is used, the DRC is first run for a few steps until the atoms have a significant velocity.  This is when the kinetic energy amounts to 0.2 kcal/mol.  When that happens, the kinetic energy is increased suddenly by n.nn kcal/mol.  The next few steps will show errors in the output as the energy is added to the system.  The use of 0.2 kcal/mol is arbitrary - any small number could be used.

If a system starts off with an energy of -100 kcal/mol, and KINETIC=10 is used, the DRC will be run with a total (kinetic plus potential) of -90 kcal/mol.

In an IRC=1 or IRC=-1 calculation, at the start of the run, the geometry is shifted by an amount proportional to n.nnn. Try using 20 to begin with, in the direction of the reaction normal coordinate. A sufficiently large value will ensure that the IRC will follow the correct path, but an excessively large value will distort the shape of the top of the reaction barrier.

See VELOCITY and Dynamic and Intrinsic Reaction Coordinates for more details.