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Computational Theoretical Chemistry
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Gaussian
Gaussian
Gaussview
Gaussview
Draw/Edit Molecule
Submit Calculations
Single Point Energy
Single Point Energy
Prepare Input
Gaussian Input File
Gaussian Output File
How Single Point Energy Works
Mathematics for Nerds
Mathematics for Nerds
Born–Oppenheimer Approximation
Electronic Schrödinger Equation
Molecular Hamiltonian
Hartree Product
Slater Determinants
Hartree–Fock Approximation
Basis Set Expansion (LCAO Approximation)
Roothaan–Hall Equations
SCF Algorithm
Density Functional Theory
Hohenberg-Kohn Theorems
Kohn-Sham Equations
Exchange-Correlation Functionals
B3LYP Functional
Complete Single Point Energy Algorithm
Geometry Optimization
Geometry Optimization
Optimization Input File
Optimization Output File
How Optimization Works
Mathematics for Nerds
Mathematics for Nerds
Potential Energy Surface (PES)
Energy Gradient
Hessian Matrix
Taylor Series Expansion
Optimization Algorithm
Berny Optimization
Convergence Criteria
Complete Geometry Optimization Algorithm
Frequency Calculation
Frequency Calculation
Frequency Input File
Frequency Output File
How Optimization Works
Mathematics for Nerds
Mathematics for Nerds
Potential Energy Surface (PES) Near Equilibrium
The Harmonic Approximation
Hessian Matrix
Mass Weighted Coordinates
Normal Modes of Vibration
The Eigenvalue Problem
Vibrational Frequencies
IR Intensities
Thermodynamic Properties
Complete Frequency Algorithm
Optimization+Frequency Calculation
Optimization+Frequency Calculation
Input File
Output File
How Optimization+Frequency Works
Mathematics for Nerds
Mathematics for Nerds
Transition State Optimization
Transition State Optimization
Input File
Output File
How Optimization+Frequency Works
Mathematics for Nerds
Mathematics for Nerds
Potential Energy Surface (PES) and Stationary Points
First-Order Saddle Points
Reaction Coordinate
Hessian Matrix and Negative Curvature
Rational Function Optimization
Berny Transition State Optimization
Initial Hessian and CalcFC
Transition State Verification Using Frequency Analysis
Complete Transition State Search Algorithm
Intrinsic Reaction Coordinate (IRC)
Intrinsic Reaction Coordinate (IRC)
Input File
Output File
How IRC Works
Mathematics for Nerds
Mathematics for Nerds
Minimum Energy Path (MEP)
Reaction Path Following
Mass Weighted Coordinates
Predictor-Corrector Algorithm
Step Size and Hessian Updates.
Complete IRC Algorithm
GAMESS
GAMESS
RHF
RHF
Input
Output
How RHF Works
Mathematics for Nerds
Mathematics for Nerds
Electronic Schrödinger Equation
Born–Oppenheimer Approximation
Slater Determinants
Hartree–Fock Approximation
Fock Operator
Roothaan–Hall Equations
SCF Algorithm
Water Molecule Example
CIS
CIS
Input
Output
How CIS Works
Mathematics for Nerds
Mathematics for Nerds
From RHF to CIS
Singly Excited Slater Determinants
Configuration Interaction Wavefunction
The CIS Hamiltonian
The CIS Secular Equation
Diagonalization and Excited States
Limitations of CIS
CASSCF
CASSCF
Active Space??
Input
Output
Output
Set Up
MCSCF Iterations
Electronic States and Configuration State Functions
Optimized Orbitals and Natural Orbitals
How CASSCF Works
Mathematics for Nerds
Mathematics for Nerds
Why Hartree–Fock Fails
The Active Space Concept
Configuration State Functions (CSFs)
The CASSCF Wavefunction
The CASSCF Hamiltonian
Solving the Configuration Interaction Problem
Orbital Optimization
State-Averaged CASSCF
Density Matrices
Natural Orbitals
The Complete CASSCF Algorithm
XMCQDPT
XMCQDPT
Input
Output
How XMCQDPT Works
Mathematics for Nerds
Mathematics for Nerds
Zeroth-Order Hamiltonian
Perturbation Expansion
Effective Hamiltonian
Intermediate-State Formalism
Second-Order Energy Corrections
Final XMCQDPT Energies
The Complete XMCQDPT Algorithm
ORCA
ORCA
RHF
RHF
Input
Output
How RHF Works
Mathematics for Nerds
Mathematics for Nerds
Complete RHF Algorithm
MCTDH
MCTDH
Operator
Operator
Prerequisites
Operator-make.sh
Script Explained
Operator.f90
Generated Operator File
Mathematics for Nerds
Mathematics for Nerds
Vibrational Hamiltonian
Electronic Hamiltonian
Linear Vibronic Coupling
Quadratic Vibronic Coupling
Complete Vibronic Hamiltonian
Operator File Interpretation
Wavepacket Propagation
Wavepacket Propagation
Input
Output
Population Analysis
Absorption Spectrum
How Wave Packet Propagation Works
Mathematics for Nerds
Mathematics for Nerds
Time-Dependent Schrödinger Equation
Molecular Hamiltonian
Vibronic Hamiltonian
Linear Vibronic Coupling
Quadratic Vibronic Coupling
MCTDH Wavefunction Expansion
Single Particle Functions
Multi-Layer MCTDH (ML-MCTDH)
Dirac–Frenkel Variational Principle
Equations of Motion
Numerical Propagation Algorithms
Population Analysis
Autocorrelation Function
Absorption Spectrum
Complete Ml-MCTDH Wavepacket Propagation Algorithm
Featured Tutorials
Featured Tutorials
Featured Tutorials
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Research Areas
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Available Resources
Available Resources
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Featured Publications
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Jitendra Singh
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