The latest version of MRCC was released on July 1, 2026.
The important new features and changes are as follows.

1. A linear-scaling integral-direct explicitly correlated second-order MP2 approach. https://doi.org/10.1021/acs.jctc.5c02184

2. New CVS-IP-CIS(D), CVS-IP-ADC(2), and double hybrid methods have been implemented for the calculation of core binding energies. https://doi.org/10.1021/acs.jctc.6c00015

3. A general-order linear-scaling local coupled-cluster model (both closed and open-shell). https://doi.org/10.1021/acs.jpca.6c00607

4. Frozen natural orbital methods using coupled-cluster natural orbitals. https://doi.org/10.1021/acs.jctc.5c01424

5. A self-consistent approach for the basis-set extrapolation of Hartree-Fock energies. https://doi.org/10.1007/s11224-025-02542-2

6. Projection-based embedding techniques for open-shell systems. https://doi.org/10.1021/acs.jctc.5c00687

7. Implementation of the spin-free exact two-component one-electron (SFX2C-1e) relativistic approach. https://doi.org/10.1021/acs.jctc.6c00015

8. A domain-based local approximation has been implemented for IP-ADC(2)- and CVS-IP-ADC(2)-based methods, enabling efficient calculations for large molecular systems. https://doi.org/10.1021/acs.jctc.6c00634

9. Open-shell support has been added for CIS, TD-HF, and CIS(D) excited-state calculations.

10. The density-based basis-set correction (DBBSC) approach is now available for open-shell MP2, CCSD(T), and double-hybrid DFT calculations with local natural orbitals.

11. Local embedded subsystem (LESS) approach accelerating Huzinaga embedded HF and hybrid DFT via asymptotically constant AO and DF basis sets. https://doi.org/10.1021/acs.jctc.5c01121

12. Memory optimization for CABS and LNO-based DBBSC, especially notable for heavier elements.  

13. A couple of bugs have been fixed, and the manual has been improved.

It is recommended for every user to upgrade to this version.