  We introduce a new implementation of the coupled cluster method tailored by
matrix product states wave functions (DMRG-TCCSD), which employs the local pair
natural orbital approach (LPNO). By exploiting locality in the coupled cluster
stage of the calculation, we were able to remove some of the limitations that
hindered the application of the canonical version of the method to larger
systems and/or with larger basis sets. We assessed the accuracy of the
approximation using two systems: tetramethyleneethane (TME) and oxo-Mn(Salen).
Using the default cut-off parameters, we were able to recover over 99.7% and
99.8% of canonical correlation energy for the triplet and singlet state of TME
respectively. In case of oxo-Mn(Salen), we found out that the amount of
retrieved canonical correlation energy depends on the size of the active space
(CAS) - we retrieved over 99.6% for the larger 27 orbital CAS and over 99.8%
for the smaller 22 orbital CAS. The use of LPNO-TCCSD allowed us to perform
these calculations up to quadruple-$\zeta$ basis set amounting to 1178 basis
functions. Moreover, we examined dependance of the ground state of
oxo-Mn(Salen) on CAS composition. We found out that the inclusion of 4d$_{xy}$
orbital plays an important role in stabilizing the singlet state at the
DMRG-CASSCF level via double-shell effect. However, by including dynamic
correlation the ground state was found to be triplet regardless of the size of
the basis set or composition of CAS, which is in agreement with previous
findings by canonical DMRG-TCCSD in smaller basis.
