1.3 Q-Chem Features

1.3.1 New Features in Q-Chem 5.2

  • Changes in default settings:

    • Single-node shared-memory parallelism becomes default and recommended for most jobs. New command line key -mpi is required to use distributed-memory MPI-parallel features (Section 2.8).

    • Pure basis functions are used by default with BASIS=GEN.

    • Default number of grid points in Lebedev grids in solvent models changed from 302 to 194 points (non-Hydrogen) and 110 points (Hydrogen) atoms.

    • Use of SWIG charges for SMx models.

    • Input format for XPol, SAPT and XSAPT, and MBE jobs has changed.

    • Use EDA2 as the default driver for ALMO-EDA.

    • Frozen core approximation no longer applied by default in RAS-CI calculations.

  • General improvements:

    • Increased availability of basis sets: High angular momentum basis functions (up to k-functions) supported for most SCF, RI-MP2, CC, EOM-CC, ADC calculations.

    • Streamlined input format for RI-SCF calculations.

    • Added the def2- family of density fitted (RI) basis sets for SCF and post-SCF calculations (Courtesy of Dr. Florian Weigend).

    • On-the-fly generation for the superposition of atomic densities guess for SCF (K. Fenk, J. Herbert).

    • Reintroduction of legacy ECPs without fitting.

    • Easy specification of basis sets on fragments, reading of basis sets from an external file (Z. Pei and Y. Shao).

  • Improvements to the DFT capabilities:

    • Support for analytic frequency calculations using meta-GGA density functinoals (available only with shared-memory parallelism).

    • Support for analytic frequency calculations using resolution-of-the-identity (density-fitted) Coulomb (available only with shared-memory parallelism).

    • Improved performance of analytic partial hessian calculations using DFT.

    • New density functionals: revM06, revM11 (P. Morgante and R. Peverati).

  • Improvements in implicit solvation models:

    • Revised PCM tessellation grids for improved performance (J. Herbert).

    • Improved performance of the general SCF program with SMx solvation models (Y. Mao).

  • New MP2 features:

    • Addition of regularized orbital-optimized second-order Møller-Plesset perturbation theory (κ-OOMP2) (J. Lee, M. Head-Gordon; Section 6.6.5).

  • Enhancements to the coupled-cluster package:

    • Mixed-precision CCSD and EOM-CCSD (P. Pokhilko, E. Epifanovsky, A.I. Krylov, with contributions from I. Kaliman, K. Nanda, M. Vidal, S. Coriani; Sections 6.15 and 7.8.5.1).

    • Damped response, dynamic polarizabilities for two-electron absorption using EOM-CC (K. Nanda and A.I. Krylov).

    • Improved evaluation of spin-orbit coupling constants across EOM-CC states (P. Pokhilko and A.I. Krylov).

    • Better handling of linear point groups in ADC and CC methods.

    • Improved performance of disk-based ADC/CC algorithms.

    • Projected and Voronoi CAP for CAP-EOM-CC/CC calculations (K. Bravaya, A. Kunitsa; Section 7.8.6).

    • Dynamic polarizabilities for CCSD and EOM-CCSD (K. Nanda, A.I. Krylov; Section 7.8.16.4).

    • New feaures for SOC calculation and analysis (P. Pokhilko, A.I. Krylov; Section 7.8.16.2).

    • Dyson orbitals for CVS-EOM-CCSD (M. Vidal, S. Coriani, A.I. Krylov; Section 7.8.5).

  • Improvements in energy decomposition analysis methods:

    • Added electron density difference (EDD) plots and the ETS-NOCV analysis (Y. Mao).

    • Added support for PCM and SMD solvation models in ALMO-EDA (Y. Mao).

    • Resolved several issues that caused instabilities in MP2-EDA calculations (Y. Mao).

  • New capabilities for explicit solvation modeling:

    • Polarizable Embedding (PE) Model for ground-state and ADC calculations (M. Scheurer; Section 12.8).

  • Other new methods and capabilities:

    • Incremental FCI method (P. Zimmerman).

    • Transition potential DFT for core-valence excitations.

    • Analytic evaluation of Raman intensities (Z. Pei and Y. Shao).