1.3 Q-Chem Features

1.3.13 Summary of Features Prior to Q-Chem 3.0

(May 16, 2021)
  • Efficient algorithms for large-molecule density functional calculations:

    • CFMM for linear scaling Coulomb interactions (energies and gradients) (C. A. White).

    • Second-generation J-engine and J-force engine (Y. Shao).

    • LinK for exchange energies and forces (C. Ochsenfeld and C. A. White).

    • Linear scaling DFT exchange-correlation quadrature.

  • Local, gradient-corrected, and hybrid DFT functionals:

    • Slater, Becke, GGA91 and Gill ‘96 exchange functionals.

    • VWN, PZ81, Wigner, Perdew86, LYP and GGA91 correlation functionals.

    • EDF1 exchange-correlation functional (R. Adamson).

    • B3LYP, B3P and user-definable hybrid functionals.

    • Analytical gradients and analytical frequencies.

    • SG-0 standard quadrature grid (S.-H. Chien).

    • Lebedev grids up to 5294 points (S. T. Brown).

  • High level wave function-based electron correlation methods

    • Efficient semi-direct MP2 energies and gradients.

    • MP3, MP4, QCISD, CCSD energies.

    • OD and QCCD energies and analytical gradients.

    • Triples corrections (QCISD(T), CCSD(T) and OD(T) energies).

    • CCSD(2) and OD(2) energies.

    • Active space coupled cluster methods: VOD, VQCCD, VOD(2).

    • Local second order Møller-Plesset (MP2) methods (DIM and TRIM).

    • Improved definitions of core electrons for post-HF correlation (V. A. Rassolov).

  • Extensive excited state capabilities:

    • CIS energies, analytical gradients and analytical frequencies.

    • CIS(D) energies.

    • Time-dependent density functional theory energies (TDDFT).

    • Coupled cluster excited state energies, OD and VOD (A. I. Krylov).

    • Coupled-cluster excited-state geometry optimizations.

    • Coupled-cluster property calculations (dipoles, transition dipoles).

    • Spin-flip calculations for CCSD and TDDFT excited states (A. I. Krylov and Y. Shao).

  • High performance geometry and transition structure optimization (J. Baker):

    • Optimizes in Cartesian, Z-matrix or delocalized internal coordinates.

    • Impose bond angle, dihedral angle (torsion) or out-of-plane bend constraints.

    • Freezes atoms in Cartesian coordinates.

    • Constraints do not need to be satisfied in the starting structure.

    • Geometry optimization in the presence of fixed point charges.

    • Intrinsic reaction coordinate (IRC) following code.

  • Evaluation and visualization of molecular properties

    • Onsager, SS(V)PE and Langevin dipoles solvation models.

    • Evaluate densities, electrostatic potentials, orbitals over cubes for plotting.

    • Natural Bond Orbital (NBO) analysis.

    • Attachment/detachment densities for excited states via CIS, TDDFT.

    • Vibrational analysis after evaluation of the nuclear coordinate Hessian.

    • Isotopic substitution for frequency calculations (R. Doerksen).

    • NMR chemical shifts (J. Kussmann).

    • Atoms in Molecules (AIMPAC) support (J. Ritchie).

    • Stability analysis of SCF wave functions (Y. Shao).

    • Calculation of position and momentum molecular intracules A. Lee, N. A. Besley, and D. P. O’Neill).

  • Flexible basis set and effective core potential (ECP) functionality: (Ross Adamson and Peter Gill)

    • Wide range of built-in basis sets and ECPs.

    • Basis set superposition error correction.

    • Support for mixed and user-defined basis sets.

    • Effective core potentials for energies and gradients.

    • Highly efficient PRISM-based algorithms to evaluate ECP matrix elements.

    • Faster and more accurate ECP second derivatives for frequencies.