  Using the classical molecular dynamics and the semiempirical Brenner's
potential, we theoretically study the interlayer sigma bond formation, as
cooperative and nonlinear phenomena induced by visible light excitations of a
graphite crystal. We have found several cases, wherein the excitations of
certain lattice sites result in new interlayer bonds even at non-excited sites.
We have also found that, a new interlayer bond is easier to be formed around a
bond, if it is already existing. As many more sites are going to be excited,
the number of interlayer bonds increases nonlinearly with the number of excited
sites. This nonlinearity shows 1.7 power of the total number of excited sites,
corresponding to about three- or four-photon process.
