"Quantum chemistry stubs" likely refers to small, incomplete entries or frameworks related to quantum chemistry in a database, research repository, or knowledge base. The term "stub" is commonly used in collaborative platforms like Wikipedia or scientific databases to denote articles that are underdeveloped or in need of expansion. Such stubs often provide a basic introduction to a topic, outlining fundamental concepts, key figures, or relevant theories without going into comprehensive detail.
AM1* (also referred to as AM1 or Austin Model 1) is a semi-empirical quantum chemistry method used for molecular modeling and calculations. It's an extension of the original AM1 method, which was developed to provide a balance between computational efficiency and accuracy for large molecules, particularly organic compounds. The AM1 method simplifies the quantum mechanical calculations by using empirical parameters derived from experimental data, allowing for the approximation of molecular orbitals and electronic structures.
AMPAC, or the American Pacific Corporation, is a company that operates in various sectors, primarily focusing on the aerospace and defense industries. However, the name "AMPAC" can also refer to different entities or organizations, depending on the context.
Ab initio multiple spawning (AIMS) is a computational method used in quantum chemistry and molecular dynamics to study the dynamics of quantum systems, particularly in situations where electronic states are coupled, such as in photochemical reactions or nonadiabatic processes. It combines concepts from the Born-Oppenheimer approximation and nonadiabatic dynamics, allowing for the simulation of complex processes involving multiple electronic states.
The Austin Model 1, often referred to simply as the Austin 1, is a car that was produced by the British automotive manufacturer Austin. It was part of the Austin Mini family, known for its compact size and distinctive design. The Mini was conceived in the late 1950s and aimed to provide an economical and efficient vehicle for urban driving. The Austin 1 was designed to be a small car with a front-wheel-drive layout, which allowed for a spacious interior despite its small footprint.
The Bohr model is primarily a model of the atom rather than specifically a model of chemical bonding. Proposed by Niels Bohr in 1913, it describes the structure of the hydrogen atom and explains how electrons inhabit quantized energy levels around the nucleus. In the Bohr model, electrons orbit the nucleus in fixed paths or orbits, and each orbit corresponds to a specific energy level. Electrons can jump from one orbit to another by absorbing or emitting energy in the form of photons.
CHELPG stands for "CHELPA," which is an acronym used in various contexts but does not specifically denote a widely recognized concept on its own. It’s possible that it could refer to something specific within a certain field, organization, or project that is not widely known.
CNDO/2, which stands for **Complete Neglect of Differential Overlap, version 2**, is a semi-empirical quantum chemistry method used to approximate the electronic structure of molecules. It is part of the broader class of semi-empirical molecular orbital (MO) methods, which simplify the full quantum mechanical calculations by making certain approximations to reduce computational demands.
Complete Active Space (CAS) is a concept used in quantum chemistry and computational chemistry to deal with electron correlation in many-body systems. It involves the selection of a specific subset of molecular orbitals considered "active" for the computational treatment of electrons while the rest of the orbitals are treated in a different way (often as filled or unfilled orbitals).
The Coulomb operator is a mathematical operator that describes the interaction between charged particles due to electrostatic forces. In the context of quantum mechanics and quantum chemistry, it is most commonly used to represent the potential energy arising from the Coulomb attraction or repulsion between charged particles, such as electrons and nuclei.
DFTB stands for Density Functional Tight Binding. It is a computational method used in quantum chemistry and solid-state physics to study the electronic structure of materials. DFTB is an approximate method that simplifies the calculations associated with Density Functional Theory (DFT) by combining aspects of tight-binding models with density functional approximations.
DMol3 is a computational chemistry software package used for molecular modeling and simulation, primarily based on density functional theory (DFT) and other quantum mechanical methods. It is part of the materials simulation suite of software developed by BIOVIA, which was formerly known as Accelrys. DMol3 allows researchers to perform calculations on molecular systems to study their electronic structure, molecular dynamics, and various properties.
"DP code" can refer to several different concepts, depending on the context in which it's used. Here are a few interpretations: 1. **Dynamic Programming (DP)**: In computer science, DP stands for dynamic programming, which is a method for solving complex problems by breaking them down into simpler subproblems. It is commonly used in algorithms and involves storing the results of subproblems to avoid redundant calculations.
Dirac is a versatile software framework designed primarily for the development, testing, and deployment of complex applications, typically in the fields of mathematical modeling, simulation, and data analysis. It is particularly known for its ability to manage dependencies and facilitate reproducibility in research environments.
Direct quantum chemistry, often referred to in the context of computational chemistry, involves methods that enable the direct calculation of molecular properties and reactions using quantum mechanical principles without relying on empirical parameters or pre-calculated data. This approach utilizes quantum mechanics to solve the Schrödinger equation for systems of many electrons and nuclei, allowing for highly accurate predictions of molecular behavior.
The double-exchange mechanism is a concept in solid-state physics and materials science that explains the behavior of electrons in certain types of materials, particularly in relation to ferromagnetism and electron transport. It describes how the movement of one type of electron can be coupled with the spin state of another electron, leading to unique magnetic and electrical properties.
The Dyall Hamiltonian is a mathematical formulation used in quantum chemistry, particularly in the context of relativistic effects in the study of heavy atoms and molecules. It is named after the physicist and chemist Prof. G. M. Dyall, who contributed to the development of methods for incorporating relativity in electronic structure calculations.
Electronic structure refers to the arrangement and behavior of electrons in an atom or molecule. It encompasses the distribution of electrons among various energy levels, subshells, and orbitals, as well as their interactions with one another. The electronic structure is fundamental to understanding the chemical properties and reactivity of elements and compounds.
Gaussian Quantum Monte Carlo (GQMC) is a computational technique used to perform quantum simulations, particularly of many-body quantum systems. It blends principles from quantum mechanics and Monte Carlo methods, with a focus on leveraging Gaussian states and distributions to simplify calculations or enhance efficiency. ### Key Aspects of Gaussian Quantum Monte Carlo: 1. **Quantum States**: GQMC typically works within the framework of Gaussian states, which are quantum states characterized by their first and second moments (mean and covariance).
Generalized Valence Bond (GVB) theory is a theoretical framework used in quantum chemistry to describe the electronic structure of molecules. It can be viewed as a hybrid approach that combines aspects of both valence bond (VB) theory and molecular orbital (MO) theory to provide a more accurate description of molecular bonding and electron correlation.
The graphical unitary group approach is a concept that arises in the context of quantum mechanics and quantum computing, particularly in the study of quantum gates and operations. This approach combines elements of graph theory with the mathematical structure of unitary groups, which are central to the formulation of quantum mechanics. ### Key Concepts: 1. **Unitary Groups**: In quantum mechanics, operations on quantum states are represented by unitary operators.
The Grimm–Sommerfeld rule is a principle used in quantum mechanics that helps to estimate the transition rates between quantum states, particularly in the context of atomic and molecular transitions. It provides a way to understand the selection rules governing the allowed or forbidden transitions between different energy levels of a quantum system. The rule was formulated by the physicists Wilhelm Grimm and Arnold Sommerfeld, and it applies primarily to electric dipole transitions.
HOMO and LUMO are terms used in molecular orbital theory to describe the highest occupied molecular orbital and the lowest unoccupied molecular orbital, respectively. These concepts are important in understanding the electronic structure of molecules, particularly in fields like chemistry and materials science. 1. **HOMO (Highest Occupied Molecular Orbital)**: - The HOMO is the molecular orbital that contains the highest energy electrons in a molecule. It is the most energetic orbital that is completely filled with electrons.
"INDO" can refer to different things depending on the context: 1. **Geographical Reference**: It often refers to India and the Indian subcontinent, sometimes used in discussions about culture, geography, or politics. 2. **Stock Market**: INDO is also the ticker symbol for the Indo Global Exchange, which can represent financial instruments like stocks or indices related to Indian markets.
The **International Journal of Quantum Chemistry** is a peer-reviewed scientific journal that focuses on the field of quantum chemistry, which involves the application of quantum mechanics to chemical systems. The journal publishes original research articles, reviews, and theoretical studies that contribute to the understanding of molecular structure, dynamics, and interactions at a quantum mechanical level. Topics covered may include computational methods, quantum chemical theories, and various applications of quantum chemistry in areas like materials science, biochemistry, and nanotechnology.
The term "local structure" can have different meanings depending on the context in which it is used. Here are a few common interpretations: 1. **Mathematics/Geometry**: In this context, local structure refers to the properties or behavior of a space or object in a small neighborhood around a point.
MINDO, which stands for MInimal N-on-Diagonal Order, is a theoretical model used in computational chemistry, specifically for estimating molecular energies and properties. It is part of the larger family of semi-empirical quantum chemistry methods, which simplify the computational process by approximating certain integrals and parameters based on experimental data or simpler calculations.
Multireference Configuration Interaction (MRCI) is a sophisticated computational chemistry method used to account for electronic correlation in molecular systems, particularly when dealing with situations where single-reference methods (like Configuration Interaction, CI, or Hartree-Fock) fail to adequately describe the electronic structure. This typically occurs in systems where there are multiple nearly-degenerate states or when the system exhibits strong correlation effects, such as in transition states, excited states, or systems with open shells.
NDDO can refer to several things, depending on the context. However, the most common references are: 1. **NDDO (National Digital Data Outlet)**: This may refer to platforms or organizations that provide access to digital data related to various fields, such as health, education, or environmental information. 2. **Network Data Distribution Object**: In computer science, this term might relate to frameworks or protocols used in data distribution across networked systems.
ONIOM (Our own N-layered Integrated molecular Orbital and molecular Mechanics) is a computational methodology used in quantum chemistry and computational chemistry to model large molecular systems. It is particularly useful for studying systems where certain regions require high-level quantum mechanical treatment, while others can be approximated with lower-level methods. The ONIOM approach divides the molecular system into different layers, each treated with a different level of theory.
ORCA is a computational quantum chemistry program designed to perform a variety of quantum mechanical calculations on molecular systems. It is particularly known for its versatility and efficiency and is used by researchers in fields such as chemistry, material science, and biochemistry. The package is capable of performing a range of methods, including: 1. **Density Functional Theory (DFT)**: ORCA supports numerous DFT functionals, making it suitable for studying electron densities and energy landscapes.
Orbital-free density functional theory (OF-DFT) is a computational approach within the framework of density functional theory (DFT) that aims to describe the electronic structure of systems without explicitly considering the electronic wavefunctions (orbitals). Traditional DFT typically relies on the Kohn-Sham equations, which involve solving for the single-particle orbitals of electrons in a potential determined by electronic density.
QMC@Home is a distributed computing project that aims to harness the power of volunteer computing resources to perform quantum Monte Carlo (QMC) calculations. These calculations are crucial for simulating quantum systems, which can be highly complex and resource-intensive. By allowing volunteers to contribute their computing power, QMC@Home seeks to make significant advancements in the field of quantum physics and materials science.
Quadratic Configuration Interaction (QCI) is a method used in quantum chemistry to describe electronic correlation effects in many-body systems, particularly in the context of molecular electronic structure calculations. It is an extension of Configuration Interaction (CI) methods, aiming to improve the accuracy of predictions regarding the electronic properties of molecules. ### Key Features of QCI: 1. **Configuration Interaction Framework**: - CI methods involve the linear combination of various electronic configurations (determinants) to capture electron correlation.
Reptation Monte Carlo (RMC) is a computational method used primarily in the study of polymer dynamics. It combines elements of Monte Carlo simulations with concepts from reptation theory, which describes the motion of polymer chains as they move through a complex medium, often mimicking the behavior of entangled polymers.
Restricted open-shell Hartree-Fock (ROHF) is a computational chemistry method used to approximate the electronic structure of molecules, particularly those that contain unpaired electrons and may have an open-shell configuration. It is a variation of the Hartree-Fock (HF) method, which solves the Hartree-Fock equations to determine the wave function and energy of a multi-electron system. Here's a breakdown of the key aspects of ROHF: 1. **Open-shell vs.
The Roothaan equations are a set of integral equations that arise in the context of Hartree-Fock (HF) theory, which is a fundamental method in quantum chemistry for approximating the electronic structure of atoms and molecules. The Roothaan equations specifically provide a way to solve for molecular orbitals in a self-consistent field approximation. In essence, the Roothaan equations are derived from the variational principle applied to the Hartree-Fock method and can be written in matrix form.
"SAM1" could refer to several different things depending on the context. Here are a few possibilities: 1. **Scientific Research**: In various fields, SAM1 might refer to a specific protein, gene, or molecule, particularly in genetic and biochemical studies. 2. **Software or Technical Terminology**: It could be a name or designation for a software application, system, or protocol.
SINDO can refer to different things depending on the context. One well-known meaning is "Sindone," often associated with the Shroud of Turin, an ancient linen cloth believed by some to bear the image of Jesus Christ. Additionally, "SINDO" could refer to an abbreviation or an acronym in a specific field, organization, or community, but without more context, it's hard to identify its exact meaning in your case.
Size consistency and size extensivity are two important concepts in the context of quantum mechanics and many-body physics, particularly concerning the properties of wave functions and the calculation of observables. ### Size Consistency **Size Consistency** refers to the requirement that the physical description of a many-body system should not depend on the size of the subsystem being considered.
Slater integrals are important quantities in the fields of atomic and solid-state physics, particularly in the context of multi-electron atomic systems and solid-state materials. They are used to describe the effects of electron-electron interactions in systems with multiple electrons, such as atoms and molecules. In quantum mechanics, the interaction between electrons is governed by their Coulomb repulsion.
State-universal coupled cluster (SUCC) theory is an extension of traditional coupled cluster (CC) methods in quantum chemistry that aims to systematically describe excited states and ground states of many-body quantum systems. **Traditional Coupled Cluster Theory**: Coupled cluster methods are widely used in quantum chemistry to solve the many-body Schrödinger equation. They are particularly powerful for calculating ground state properties of quantum systems.
An unpaired electron refers to an electron in an atom or molecule that is alone in its orbital and does not have a corresponding electron with opposite spin. Electrons occupy atomic orbitals in pairs, with one electron spinning in one direction (spin-up) and the other in the opposite direction (spin-down). When an orbital contains a single electron, that electron is considered an unpaired electron. Unpaired electrons are significant in determining the chemical properties and reactivity of atoms and molecules.
Vacuum level refers to the measure of pressure in a vacuum system relative to atmospheric pressure. It indicates how much lower the pressure is compared to the surrounding atmospheric pressure. Vacuum levels are typically expressed in units of pressure such as pascals (Pa), torr, millimeters of mercury (mmHg), or inches of mercury (inHg). In practical terms, vacuum levels can be categorized into different ranges: 1. **Low Vacuum**: Approximately 0.
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