tcp -truncated Coulomb potential control variable
DESCRIPTION
The tcp variable determines the use of a truncated Coulomb
potential in the calculation of the electrostatic energy. If tcp
is set to ON, the Coulomb potential (1/r) used in the calculation
of the electrostatic energy is replaced by
v(r) = ( 1 / r ) * 0.5 * erfc( (r - tcp_rcut) / tcp_sigma )
The variable tcp_rcut limits the
range of the Coulomb potential. The variable tcp_sigma
determines
the width of the truncation region. The tcp variable can be used
to compute the energy of a charged system without including the electrostatic
energy of interaction between periodic replica of the system. Using the
tcp variable allows for a meaningful comparison of the energies
of charged and neutral systems. This is necessary e.g. for the determination
of ionization potentials or electron affinities.
DEFAULT VALUE
OFF
ALLOWED VALUES
ON, OFF
RELATED INFORMATION