The command Empty(R) returns the empty regular chain of R, that is the regular chain of R with no polynomials.

This command is part of the RegularChains[ChainTools] package, so it can be used in the form Empty(..) only after executing the command with(RegularChains[ChainTools]).  However, it can always be accessed through the long form of the command by using RegularChains[ChainTools][Empty](..).