Configuration interactionConfiguration interaction (CI) is a post-Hartree–Fock linear variational method for solving the nonrelativistic Schrödinger equation within the Born–Oppenheimer approximation for a quantum chemical multi-electron system. Mathematically, configuration simply describes the linear combination of Slater determinants used for the wave function.
Multi-configurational self-consistent fieldMulti-configurational self-consistent field (MCSCF) is a method in quantum chemistry used to generate qualitatively correct reference states of molecules in cases where Hartree–Fock and density functional theory are not adequate (e.g., for molecular ground states which are quasi-degenerate with low-lying excited states or in bond-breaking situations).
Good quantum numberIn quantum mechanics, the eigenvalue q{\displaystyle q} of an observableO{\displaystyle O} is said to be a good quantum number if the observable O{\displaystyle O} is a constant of motion. In other words, the quantum number is good if the corresponding observable commutes with the Hamiltonian.
Electron configurationIn atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom is 1s 2s 2p, meaning that the 1s, 2s, and 2p subshells are occupied by two, two, and six electrons, respectively.
Slater determinantIn quantum mechanics, a Slater determinant is an expression that describes the wave function of a multi-fermionic system. It satisfies anti-symmetry requirements, and consequently the Pauli principle, by changing sign upon exchange of two fermions. Only a small subset of all possible many-body fermionic wave functions can be written as a single Slater determinant, but those form an important and useful subset because of their simplicity.
Wave functionMathematical description of quantum stateQuantum harmonic oscillators for a single spinless particle. The oscillations have no trajectory, but are instead represented each as waves; the vertical axis shows the real part (blue) and imaginary part (red) of the wave function. Panels A–D show four different standing-wave solutions of the Schrödinger equation.
Angular momentumAngular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of linear momentum. It is an important physical quantity because it is a conserved quantity – the total angular momentum of an isolated system remains constant. Angular momentum has both a direction and a magnitude, and both are conserved. Bicycles and motorcycles, flying discs, rifled bullets, and gyroscopes owe their useful properties to conservation of angular momentum.
CombinationIn mathematics, a combination is a selection of items from a set that has distinct members, such that the order of selection does not matter (unlike permutations). For example, given three fruits, say an apple, an orange and a pear, there are three combinations of two that can be drawn from this set: an apple and a pear; an apple and an orange; or a pear and an orange.
Linear combinationIn mathematics, a linear combination or superposition is an expression constructed from a set of terms by multiplying each term by a constant and adding the results (e.g. a linear combination of x and y would be any expression of the form ax + by, where a and b are constants). The concept of linear combinations is central to linear algebra and related fields of mathematics.
Spin (physics)Intrinsic quantum property of particlesSpin is an intrinsic form of angular momentum carried by elementary particles, and thus by composite particles such as hadrons, atomic nuclei, and atoms. Spin is quantized, and accurate models for the interaction with spin require relativistic quantum mechanics or quantum field theory.
Quantum chemistryQuantum chemistry, or molecular quantum mechanics, is a branch of physical chemistry which applies quantum mechanics to chemical systems to predict physical and chemical properties of molecules and materials. It often involves calculating electronic wave functions at the atomic level.Hamiltonian matrixIn mathematics, a Hamiltonian matrix is a 2n-by-2n matrix A such that JA is symmetric, where J is the skew-symmetric matrix J = [ 0 n I n − I n 0 n ] {\displaystyle J={\begin{bmatrix}0_{n}&I_{n}\\-I_{n}&0_{n}\end{bmatrix}}} and In is the n-by-n identity matrix. In other words, A is Hamiltonian if and only if (JA)T = JA where ( )T denotes the transpose.
Multi-configurational self-consistent fieldMulti-configurational self-consistent field (MCSCF) is a method in quantum chemistry used to generate qualitatively correct reference states of molecules in cases where Hartree–Fock and density functional theory are not adequate (e.g., for molecular ground states which are quasi-degenerate with low-lying excited states or in bond-breaking situations).Good quantum numberIn quantum mechanics, the eigenvalue q{\displaystyle q} of an observableO{\displaystyle O} is said to be a good quantum number if the observable O{\displaystyle O} is a constant of motion. In other words, the quantum number is good if the corresponding observable commutes with the Hamiltonian.Electron configurationIn atomic physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom is 1s 2s 2p, meaning that the 1s, 2s, and 2p subshells are occupied by two, two, and six electrons, respectively.Slater determinantIn quantum mechanics, a Slater determinant is an expression that describes the wave function of a multi-fermionic system. It satisfies anti-symmetry requirements, and consequently the Pauli principle, by changing sign upon exchange of two fermions. Only a small subset of all possible many-body fermionic wave functions can be written as a single Slater determinant, but those form an important and useful subset because of their simplicity.Wave functionMathematical description of quantum stateQuantum harmonic oscillators for a single spinless particle. The oscillations have no trajectory, but are instead represented each as waves; the vertical axis shows the real part (blue) and imaginary part (red) of the wave function. Panels A–D show four different standing-wave solutions of the Schrödinger equation.Angular momentumAngular momentum (sometimes called moment of momentum or rotational momentum) is the rotational analog of linear momentum. It is an important physical quantity because it is a conserved quantity – the total angular momentum of an isolated system remains constant. Angular momentum has both a direction and a magnitude, and both are conserved. Bicycles and motorcycles, flying discs, rifled bullets, and gyroscopes owe their useful properties to conservation of angular momentum.CombinationIn mathematics, a combination is a selection of items from a set that has distinct members, such that the order of selection does not matter (unlike permutations). For example, given three fruits, say an apple, an orange and a pear, there are three combinations of two that can be drawn from this set: an apple and a pear; an apple and an orange; or a pear and an orange.Linear combinationIn mathematics, a linear combination or superposition is an expression constructed from a set of terms by multiplying each term by a constant and adding the results (e.g. a linear combination of x and y would be any expression of the form ax + by, where a and b are constants). The concept of linear combinations is central to linear algebra and related fields of mathematics.Spin (physics)Intrinsic quantum property of particlesSpin is an intrinsic form of angular momentum carried by elementary particles, and thus by composite particles such as hadrons, atomic nuclei, and atoms. Spin is quantized, and accurate models for the interaction with spin require relativistic quantum mechanics or quantum field theory.Quantum chemistryQuantum chemistry, or molecular quantum mechanics, is a branch of physical chemistry which applies quantum mechanics to chemical systems to predict physical and chemical properties of molecules and materials. It often involves calculating electronic wave functions at the atomic level.Hamiltonian matrixIn mathematics, a Hamiltonian matrix is a 2n-by-2n matrix A such that JA is symmetric, where J is the skew-symmetric matrix J = [ 0 n I n − I n 0 n ] {\displaystyle J={\begin{bmatrix}0_{n}&I_{n}\\-I_{n}&0_{n}\end{bmatrix}}} and In is the n-by-n identity matrix. In other words, A is Hamiltonian if and only if (JA)T = JA where ( )T denotes the transpose.*As an Amazon Associate I earn from qualifying purchases.