- 1 Introduction
- 2 Installation, Customization, and Execution
- 2.1 Installation Requirements
- 2.2 Installing Q-Chem
- 2.3 Q-Chem Auxiliary files ($QCAUX)
- 2.4 Q-Chem Run-time Environment Variables
- 2.5 User Account Adjustments
- 2.6 Further Customization: .qchemrc and preferences Files
- 2.7 Running Q-Chem
- 2.8 Parallel Q-Chem Jobs
- 2.9 IQmol Installation Requirements
- 2.10 Testing and Exploring Q-Chem
- 3 Q-Chem Inputs
- 4 Self-Consistent Field Ground-State Methods
- 4.1 Overview
- 4.2 Theoretical Background
- 4.3 Basic SCF Job Control
- 4.4 SCF Initial Guess
- 4.5 Converging SCF Calculations
- 4.6 Large Molecules and Linear Scaling Methods
- 4.7 Dual-Basis Self-Consistent Field Calculations
- 4.8 Hartree-Fock and Density-Functional Perturbative Corrections
- 4.9 Unconventional SCF Calculations
- 4.10 Ground State Method Summary
- 5 Density Functional Theory
- 5.1 Introduction
- 5.2 Kohn-Sham Density Functional Theory
- 5.3 Overview of Available Functionals
- 5.4 Basic DFT Job Control
- 5.5 DFT Numerical Quadrature
- 5.6 Range-Separated Hybrid Density Functionals
- 5.7 DFT Methods for van der Waals Interactions
- 5.8 Empirical Corrections for Basis Set Superposition Error
- 5.9 Double-Hybrid Density Functional Theory
- 5.10 Asymptotically Corrected Exchange-Correlation Potentials
- 5.11 Derivative Discontinuity Restoration
- 5.12 Thermally-Assisted-Occupation Density Functional Theory (TAO-DFT)
- 5.13 Methods Based on “Constrained” DFT
- 6 Wave Function-Based Correlation Methods
- 6.1 Introduction
- 6.2 Treatment and the Definition of Core Electrons
- 6.3 Møller-Plesset Perturbation Theory
- 6.4 Exact MP2 Methods
- 6.5 Local MP2 Methods
- 6.6 Auxiliary Basis (Resolution of the Identity) MP2 Methods
- 6.7 Attenuated MP2
- 6.8 Coupled-Cluster Methods
- 6.9 Non-iterative Corrections to Coupled Cluster Energies
- 6.10 Coupled Cluster Active Space Methods
- 6.11 Frozen Natural Orbitals in CCD, CCSD, OD, QCCD, and QCISD Calculations
- 6.12 Non-Hartree-Fock Orbitals in Correlated Calculations
- 6.13 Analytic Gradients and Properties for Coupled-Cluster Methods
- 6.14 Memory Options and Parallelization of Coupled-Cluster Calculations
- 6.15 Simplified Coupled-Cluster Methods Based on a Perfect-Pairing Active Space
- 6.16 Geminal Models
- 7 Open-Shell and Excited-State Methods
- 7.1 General Excited-State Features
- 7.2 Uncorrelated Wave Function Methods
- 7.3 Time-Dependent Density Functional Theory (TDDFT)
- 7.4 Maximum Overlap Method (MOM) for SCF Excited States
- 7.5 Restricted Open-Shell Kohn-Sham Method for
-SCF Calculations of Excited States
- 7.6 Correlated Excited State Methods: The CIS(D) Family
- 7.7 Coupled-Cluster Excited-State and Open-Shell Methods
- 7.8 Correlated Excited State Methods: The ADC(
) Family
- 7.9 Restricted Active Space Spin-Flip (RAS-SF) and Configuration Interaction (RAS-CI)
- 7.10 Core Ionization Energies and Core-Excited States
- 7.11 Real-Time SCF Methods (RT-TDDFT, RT-HF, OSCF2)
- 7.12 Visualization of Excited States
- 8 Basis Sets
- 9 Effective Core Potentials
- 10 Exploring Potential Energy Surfaces: Critical Points and Molecular Dynamics
- 10.1 Equilibrium Geometries and Transition-State Structures
- 10.2 Improved Algorithms for Transition-Structure Optimization
- 10.3 Constrained Optimization
- 10.4 Potential Energy Scans
- 10.5 Intrinsic Reaction Coordinate
- 10.6 Nonadiabatic Couplings and Optimization of Minimum-Energy Crossing Points
- 10.7 Ab Initio Molecular Dynamics
- 10.8 Ab initio Path Integrals
- 11 Molecular Properties and Analysis
- 11.1 Introduction
- 11.2 Wave Function Analysis
- 11.3 Interface to the NBO Package
- 11.4 Orbital Localization
- 11.5 Visualizing and Plotting Orbitals, Densities, and Other Volumetric Data
- 11.6 Spin and Charge Densities at the Nuclei
- 11.7 Atoms in Molecules
- 11.8 Distributed Multipole Analysis
- 11.9 Intracules
- 11.10 Harmonic Vibrational Analysis
- 11.11 Anharmonic Vibrational Frequencies
- 11.12 Linear-Scaling Computation of Electric Properties
- 11.13 NMR and Other Magnetic Properties
- 11.14 Finite-Field Calculation of (Hyper)Polarizabilities
- 11.15 General Response Theory
- 11.16 Electronic Couplings for Electron- and Energy Transfer
- 11.17 Population of Effectively Unpaired Electrons
- 11.18 Molecular Junctions
- 12 Molecules in Complex Environments: Solvent Models, QM/MM and QM/EFP Features, Density Embedding
- 13 Fragment-Based Methods
- 13.1 Introduction
- 13.2 Specifying Fragments in the $molecule Section
- 13.3 FRAGMO Initial Guess for SCF Methods
- 13.4 Locally-Projected SCF Methods
- 13.5 The First-Generation ALMO-EDA and Charge-Transfer Analysis (CTA)
- 13.6 Job Control for Locally-Projected SCF Methods
- 13.7 The Second-Generation ALMO-EDA Method
- 13.8 The MP2 ALMO-EDA Method
- 13.9 The Adiabatic ALMO-EDA Method
- 13.10 The Explicit Polarization (XPol) Method
- 13.11 Symmetry-Adapted Perturbation Theory (SAPT)
- 13.12 The XPol+SAPT (XSAPT) Method
- 13.13 Energy Decomposition Analysis based on SAPT/cDFT
- 13.14 The Many-Body Expansion Method
- 13.15 Ab Initio Frenkel Davydov Exciton Model (AIFDEM)
- 13.16 TDDFT for Molecular Interactions
- 13.17 The ALMO-CIS and ALMO-CIS+CT methods
- A Geometry Optimization with Q-Chem
- B AOInts
- B.1 Introduction
- B.2 Historical Perspective
- B.3 AOInts: Calculating ERIs with Q-Chem
- B.4 Shell-Pair Data
- B.5 Shell-Quartets and Integral Classes
- B.6 Fundamental ERI
- B.7 Angular Momentum Problem
- B.8 Contraction Problem
- B.9 Quadratic Scaling
- B.10 Algorithm Selection
- B.11 More Efficient Hartree–Fock Gradient and Hessian Evaluations
- B.12 User-Controllable Variables
- C Q-Chem Quick Reference
- D References and Further Reading