How large are post-CCSD(T) contributions to the total atomization energies of medium-sized alkanes?

• We calculate post-CCSD(T) atomization energies of n-alkanes by means of W4 theory.
• Post-CCSD(T) contributions to the TAE increase linearly with the size of the n-alkane.
• The post-CCSD(T) contributions to the TAE of hexane reach 0.65 kcal/mol.
• Post-CCSD(T) contributions to the TAE of decane are expected to exceed 1 kcal/mol.