1.3 Q-Chem Features

1.3.3 New Features in Q-Chem 5.0

  • Enhancements to the coupled-cluster package:

    • Analytic gradients for Cholesky-decomposed CCSD and EOM-CCSD; efficiency improvement for canonical CCSD and EOM-CCSD gradients (X. Feng, E. Epifanovsky).

    • CAP-EOM-CCSD analytic gradients (Z. Benda and T.-C. Jagau) and Dyson orbitals for metastable states (T.-C. Jagau, A.I. Krylov), Section 7.8.6).

    • CAP-EOM-MP2 method (A. Kunitsa, K. Bravaya).

    • Evaluation of polarizabilities using CCSD and EOM-CCSD (EE and SF) wave functions using full derivative formulation (K. Nanda and A. Krylov, Section 7.8.16.4).

    • Evaluation of S2 for EOM-CCSD wave functions (X. Feng).

    • Evaluation of NACs for EOM-CCSD wave functions (S. Faraji, A. Krylov, E. Epifanovski, X. Feng, Section 7.8.16.3).

    • Efficiency improvement and new multicore-parallel code for (T) correction (I. Kaliman).

    • New coupled-cluster based methods for core states (A. Krylov).

  • New capabilities for implicit solvation modeling:

    • PCM capabilities for computing vertical excitation, ionization, and electron attachment energies at EOM-CC and MP2 levels (Section 7.8.11).

    • State-specific equilibrium and non-equilibrium solvation for all orders and variants of ADC (J. M. Mewes and A. Dreuw; Section 7.9.7).

    • Poisson equation boundary conditions allowing use of an arbitrary, anisotropic dielectric function ε(𝐫), with full treatment of volume polarization (M. P. Coons and J. M. Herbert; Section 12.2.10).

    • Composite Model for Implicit Representation of Solvent (CMIRS), an accurate model for free energies of solvation (Section 12.2.6)

  • New density functionals (N. Mardirossian and M. Head-Gordon; Section 5.3):

    • GGA functionals: BEEF-vdW, HLE16, KT1, KT2, KT3, rVV10

    • Meta-GGA functionals: B97M-rV, BLOC, mBEEF, oTPSS, TM

    • Hybrids: CAM-QTP(00), CAM-QTP(01), HSE-HJS, LC-ωPBE08, MN15, rCAM-B3LYP, WC04, WP04

    • Double hybrids: B2GP-PLYP, DSD-PBEB95-D3, DSD-PBEP86-D3, DSD-PBEPBE-D3, LS1DH-PBE, PBE-QIDH, PTPSS-D3, PWPB95-D3

    • Grimme’s PBEh-3c “low-cost” composite method

    • rVV10 non-local correlation functional

  • Additional DFT developments:

    • New forms of DFT-D3 (J. Witte; Section 5.7.2).

    • New standard integration grids, SG-2 and SG-3 (S. Dasgupta and J. M. Herbert; Section 5.5.2).

    • More efficient propagator algorithms for real-time TDDFT (Y. Zhu and J. M. Herbert; Section 7.12).

  • New integral package for for computing effective core potential (ECP) integrals (S. C. McKenzie, E. Epifanovsky; Chapter 9).

    • More efficient analytic algorithms for energies and first derivatives.

    • Support for arbitrary projector angular momentum.

    • Support up to h angular momentum in the basis set.

  • Analytic derivative couplings for the ab initio Frenkel-Davydov exciton model (A. F. Morrison and J. M. Herbert; Section 13.16).

  • New ALMO-based energy decomposition analysis (EDA) methods:

    • The second-generation ALMO-EDA methods for DFT (P. R. Horn, Y. Mao and M. Head-Gordon; Section 13.7)

    • The extension of ALMO-EDA to RIMP2 theory (J. Thirman and M. Head-Gordon; Section 13.8)

    • The “adiabatic" EDA method for decomposing changes in molecular properties (Y. Mao, P. R. Horn and M. Head-Gordon; Section 13.9)

  • Wave function correlation capabilities:

    • Coupled cluster valence bond (CCVB) method for describing open-shell molecules with strong spin correlations (D. W. Small and M. Head-Gordon; Section 6.16.2).

    • Implementation of coupled-cluster valence bond with singles and doubles (CCVB-SD) for closed-shell species (J. Lee, D. W. Small and M. Head-Gordon; Section 6.10.4).

Note:  Several important changes in Q-Chem’s default settings have occurred since version 4.4. Core electrons are now frozen by default in most post-Hartree-Fock calculations; see Section 6.2. The keywords for calculation of SOCs and NACs were renamed for consistency between different methods. Some newer density functionals now use either the SG-2 or SG-3 quadrature grid by default, whereas all functionals used SG-1 by default in v. 4.4. Table 5.3 lists the default grid for various classes of functionals.