- 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 Runtime 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 Density Functional Theory
- 4.5 SCF Initial Guess
- 4.6 Converging SCF Calculations
- 4.7 Large Molecules and Linear Scaling Methods
- 4.8 Dual-Basis Self-Consistent Field Calculations
- 4.9 Hartree-Fock and Density-Functional Perturbative Corrections
- 4.10 Methods Based on “Constrained” DFT
- 4.11 Unconventional SCF Calculations
- 4.12 Ground State Method Summary
- 5 Wave Function-Based Correlation Methods
- 5.1 Introduction
- 5.2 Møller-Plesset Perturbation Theory
- 5.3 Exact MP2 Methods
- 5.4 Local MP2 Methods
- 5.5 Auxiliary Basis Set (Resolution-of-Identity) MP2 Methods
- 5.6 Short-Range Correlation Methods
- 5.7 Coupled-Cluster Methods
- 5.8 Noniterative Corrections to Coupled Cluster Energies
- 5.9 Coupled Cluster Active Space Methods
- 5.10 Frozen Natural Orbitals in CCD, CCSD, OD, QCCD, and QCISD Calculations
- 5.11 Non-Hartree-Fock Orbitals in Correlated Calculations
- 5.12 Analytic Gradients and Properties for Coupled-Cluster Methods
- 5.13 Memory Options and Parallelization of Coupled-Cluster Calculations
- 5.14 Simplified Coupled-Cluster Methods Based on a Perfect-Pairing Active Space
- 5.15 Geminal Models
- 6 Open-Shell and Excited-State Methods
- 6.1 General Excited-State Features
- 6.2 Uncorrelated Wave Function Methods
- 6.3 Time-Dependent Density Functional Theory (TDDFT)
- 6.4 Maximum Overlap Method (MOM) for SCF Excited States
- 6.5 Restricted Open-Shell Kohn-Sham Method for
-SCF Calculations of Excited States
- 6.6 Correlated Excited State Methods: the CIS(D) Family
- 6.7 Coupled-Cluster Excited-State and Open-Shell Methods
- 6.8 Correlated Excited State Methods: ADC(
) Family
- 6.9 Restricted active space spin-flip (RAS-SF) and configuration interaction (RAS-CI) methods
- 6.10 Core Ionization Energies and Core-Excited States
- 6.11 Real-time SCF Methods (RT-TDDFT, RT-HF, OSCF2)
- 6.12 Visualization of Excited States
- 7 Basis Sets
- 8 Effective Core Potentials
- 9 Exploring Potential Energy Surfaces: Critical Points and Molecular Dynamics
- 9.1 Equilibrium Geometries and Transition-State Structures
- 9.2 Improved Algorithms for Transition-Structure Optimization
- 9.3 Constrained Optimization
- 9.4 Potential Energy Scans
- 9.5 Intrinsic Reaction Coordinate
- 9.6 Nonadiabatic Couplings and Optimization of Minimum-Energy Crossing Points
- 9.7 Ab Initio Molecular Dynamics
- 9.8 Ab initio Path Integrals
- 10 Molecular Properties and Analysis
- 10.1 Introduction
- 10.2 Wave Function Analysis
- 10.3 Interface to the NBO Package
- 10.4 Orbital Localization
- 10.5 Visualizing and Plotting Orbitals and Densities
- 10.6 Electrostatic Potentials
- 10.7 Spin and Charge Densities at the Nuclei
- 10.8 Atoms in Molecules
- 10.9 Intracules
- 10.10 Vibrational Analysis
- 10.11 Anharmonic Vibrational Frequencies
- 10.12 NMR Shielding Tensors
- 10.13 Linear-Scaling NMR Chemical Shifts: GIAO-HF and GIAO-DFT
- 10.14 Indirect Nuclear Spin–Spin Coupling Constants
- 10.15 Linear–Scaling Computation of Electric Properties
- 10.16 Electronic Couplings for Electron Transfer and Energy Transfer
- 10.17 Calculating the Population of Effectively Unpaired Electrons with DFT
- 10.18 Quantum Transport Properties via the Landauer Approximation
- 11 Molecules in Complex Environments: Solvent Models, QM/MM and QM/EFP Features, Density Embedding
- 12 Fragment-Based Methods
- 12.1 Introduction
- 12.2 Specifying Fragments in the $molecule Section
- 12.3 FRAGMO Initial Guess for SCF Methods
- 12.4 Locally-Projected SCF Methods
- 12.5 Energy Decomposition and Charge-Transfer Analysis
- 12.6 Job Control for Locally-Projected SCF Methods
- 12.7 The Explicit Polarization (XPol) Method
- 12.8 Symmetry-Adapted Perturbation Theory (SAPT)
- 12.9 The XPol+SAPT (XSAPT) Method
- 12.10 The Many-Body Expansion Method
- 12.11 Ab-Initio Frenkel Davydov Exciton Model (AIFDEM)
- 12.12 TDDFT for Molecular Interactions
- 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