DFT AND TDDFT EXCHANGE-CORRELATION FUNCTIONALS

A large set of innovative functionals and algorithms for ground, excited, and ionized states, including:

• Dispersion Corrections:
• Becke-Johnson XDM model
• DF-04, VV09, VV10 van der Waals
• DFT-D3 long-range corrections


• General Purpose Functionals:
• M11 and M11-L hybrid meta GGAs
• Becke-05 nondynamic correlation model
• MCY2 hyper-GGA functional of Yang et al


• Double Hybrid Density Functionals
• XYG3 and XYG3-OS double hybrids
• wB97X-2 double hybrid

New functionals yield smaller errors in the barrier heights for HTBH38/04 reactions than B3LYP.

POST HARTREE-FOCK FEATURES

• Coupled-Cluster, Equation-of-Motion, and Adiabatic Diagrammatic Construction Methods:
• Significantly enhanced coupled-cluster codes rewritten for better performance on multicore systems
• Energy, gradient, and properties for CCSD, EOM-EE/SF/IP/EA-CCSD
• New EOM methods (2SF, DIP) and triples corrections for chemical accuracy


• New Approaches for Strong Correlation:
• Perfect quadruples and perfect hextuples methods for strong correlation problems
• Coupled Cluster Valence Bond (CCVB) and related methods for multiple bond breaking

EXCITED STATES AND OPEN-SHELL SPECIES

• EOM-CC Methods for Excited (EE), Ionized/Electron-Attached (IP/EA), and Diradical States (SF, DIP)
• Analytical gradients, multicore parallelization, interface with Effective Fragment Potential Method


• ADC Family of Methods Including ADC(2X)


• RI-SOS-CIS(D): N^4 Excited State Method


• Restricted Active Space Double SF Method for Polyradicals and Multiple Bond Breaking


• Non-Collinear SF-DFT (improved accuracy for multi-configurational species)


• Analytical Gradient and Hessian for TDDFT/TDA and Full TDDFT

PROPERTY ANALYSIS

• Energy Decomposition Analysis Based on Absolutely Localized MO's
• Interaction energy between fragments is divided into frozen density (Coulomb + exchange), polarization, and charge-transfer terms.


• In organometallic compunds, it shows the electron donation from ligand to metal (above left) and back donation from metal to ligand (above right).


• Electron Transfer and Excitation Energy Transfer
• CDFT leads to charge-constrained states. CDFT-CI describes configuration interaction among these constrained states.


• Direct coupling method, in its ‘1+1’ version, uses the product of fragment wavefunctions to compute the coupling.


• Fragment charge (or excitation or spin) difference methods compute ET and EET couplings between eigenstates.


• Diabatization schemes, overlap analysis


• Fast NMR Shifts Calculations (made possible with advanced solvers of reponse equations) and Much More.

The analysis shows the electron donation
from ligand to metal (above left)
and back donation from metal to ligand.

OPTIMIZATIONS, REACTION PATH, VIBRATIONAL ANALYSIS AND SIMULATION

• Automated Reaction Path Finding
• Freezing and Growing String methods


• Local Vibrational Modes with Partial Hessian Vibrational Analysis


• Tunneling and Anharmonic Effects
• Path integral Monte Carlo simulates both electronic and nuclear motions with quantum mechanics


• Simulating IR and Photoelectron Spectra
• Quasiclassical trajectories AIMD by incorporating vibrational zero-point energies into intial velocities

ENVIRONMENTAL EFFECTS: SOLVATION MODELS, EFP AND QM/MM

• Popular Solvent Models Describing Implicit Solvation Effects
• SM8, COSMO, C-PCM, SS(V)PE, IEF-PCM, and more
• C-PCM/SIWG with smooth potential energy surfaces


• Effective Fragment Potential Method Explicit Solvent Molecules Such as Water
• For both the ground and excited states
• Interfaced with DFT and wave-function based methods
• Unique feature:  Built-in library of standard effective fragments


• QM/MM Methods Treating Environment Atoms as Classical Potential
• Internal QM/MM for ground and excited states calculations
• Q-Chem’s unique Yin-Yang atom interface for QM/MM
• Integration with PCM models (QC/MM/PCM)
• External interface with CHARMM for full QM/MM hessian (or its mobile-block-hessian approximation), which allows studying vibrational entropic effects or large-scale conformational changes

COMPUTATIONAL EFFICIENCY

• Fast Algorithms for DFT Calculations
• Algorithms for Coulomb (Continuous Fast Multipole Method, J engine, Fourier Transform Coulomb, Quantum Ewald Mesh)
• Algorithms for Hartree-Fock exchange (LinK, ARI-K) and numerical integration (mrXC).


• Perturbation Theory Calculations
• Fast integral transformations, Resolution-of-Identity approximation, scaling of different spin components, Laplace transform, dual-basis extrapolation, and the use of localized orbitals.


• Coupled-Cluster Calculations
• Enhanced by a modern tensor library, Resolution-of-Identity approximation, and Cholesky decomposition.


• Efficient Implementation on Shared-Memory Multicore Machines and Computer Clusters