  A stochastic resolution of identity approach (sRI) is applied to the
second-order coupled cluster singles and doubles (CC2) model to calculate the
ground-state energy. Utilizing a set of stochastic orbitals to optimize the
expensive tensor contraction steps in CC2, we greatly reduce the overall
computational cost. Compared with the RI-CC2 model, the sRI-CC2 achieves
scaling reduction from O(N^5) to O(N^3), where N is a measure for the system
size. When applying the sRI-CC2 to a series of hydrogen dimer chains, we
demonstrate that the sRI-CC2 accurately reproduces RI-CC2 results for the
correlation energies and exhibits a scaling of O(NH^2.71), with NH being the
number of hydrogen atoms. Our calculations with different systems and basis
sets show small changes in standard deviations, which indicates a broad
applicability of our approach to various systems.
