|
MNDO
MNDO, or Modified Neglect of Diatomic Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Neglect of Diatomic Differential Overlap integral approximation. Similarly, this method replaced the earlier MINDO method. It is part of the MOPAC program and was developed in the group of Michael Dewar. It is also part of the AMPAC, GAMESS (US), PC GAMESS, GAMESS (UK), Gaussian, ORCA and CP2K programs. Later, it was essentially replaced by two new methods, PM3 and AM1, which are similar but have different parameterisation methods. The extension by W. Thiel's group, called MNDO/d, which adds d functions, is widely used for organometallic compounds. It is included in GAMESS (UK). MNDOC, also from W. Thiel's group, explicitly adds correlation effects though second order perturbation theory In mathematics and applied mathematics, perturbation theory comprises methods for finding an app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Austin Model 1
Austin Model 1, or AM1, is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Neglect of Differential Diatomic Overlap integral approximation. Specifically, it is a generalization of the modified neglect of differential diatomic overlap approximation. Related methods are PM3 and the older MINDO. AM1 was developed by Michael Dewar and co-workers and published in 1985. AM1 is an attempt to improve the MNDO model by reducing the repulsion of atoms at close separation distances. The atomic core-atomic core terms in the MNDO equations were modified through the addition of off-center attractive and repulsive Gaussian functions. The complexity of the parameterization problem increased in AM1 as the number of parameters per atom increased from 7 in MNDO to 13-16 per atom in AM1. The results of AM1 calculations are sometimes used as the starting points for parameterizations of forcefields in molec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AMPAC
AMPAC is a general-purpose semiempirical quantum chemistry program. It is marketed by Semichem, Inc. and was developed originally by Michael Dewar and his group. The first version of AMPAC (2.1) was made available in 1985 through the Quantum Chemistry Program Exchange (QCPE). Subsequent versions were released through the same source, representing minor updates and optimized versions for other platforms. In 1992, Semichem, Inc. was formed at Professor Dewar's urging to maintain and market the program. ''AMPAC 4.0 with Graphical User Interface'' was released in August of that year. Semichem's current version of AMPAC is 10.http://www.semichem.com/ AMPAC current implements the SAM1, AM1, MNDO, MNDO/d, PM3, MNDOC MINDO/3, RM1 and PM6 semi-empirical methods and AMSOL and COSMO salvation models. See also * Quantum chemistry computer programs Quantum chemistry computer programs are used in computational chemistry to implement the methods of quantum chemistry. Most include the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PM3 (chemistry)
PM3, or Parametric Method 3, is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Neglect of Differential Diatomic Overlap integral approximation. The PM3 method uses the same formalism and equations as the AM1 method. The only differences are: 1) PM3 uses two Gaussian functions for the core repulsion function, instead of the variable number used by AM1 (which uses between one and four Gaussians per element); 2) the numerical values of the parameters are different. The other differences lie in the philosophy and methodology used during the parameterization: whereas AM1 takes some of the parameter values from spectroscopical measurements, PM3 treats them as optimizable values. The method was developed by J. J. P. Stewart and first published in 1989. It is implemented in the MOPAC program (of which the older versions are public domain), along with the related RM1, AM1, MNDO and MINDO meth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CP2K
CP2K is a freely available ( GPL) quantum chemistry and solid state physics program package, written in Fortran 2008, to perform atomistic simulations of solid state, liquid, molecular, periodic, material, crystal, and biological systems. It provides a general framework for different methods: density functional theory (DFT) using a mixed Gaussian and plane waves approach (GPW) via LDA, GGA, MP2, or RPA levels of theory, classical pair and many-body potentials, semi-empirical ( AM1, PM3, MNDO, MNDOd, PM6) and tight-binding Hamiltonians, as well as Quantum Mechanics/Molecular Mechanics (QM/MM) hybrid schemes relying on the Gaussian Expansion of the Electrostatic Potential (GEEP). The Gaussian and Augmented Plane Waves method (GAPW) as an extension of the GPW method allows for all-electron calculations. CP2K can do simulations of molecular dynamics, metadynamics, Monte Carlo, Ehrenfest dynamics, vibrational analysis, core level spectroscopy, energy minimization, and transition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gaussian (software)
Gaussian is a general purpose computational chemistry software package initially released in 1970 by John Pople and his research group at Carnegie Mellon University as Gaussian 70. It has been continuously updated since then. The name originates from Pople's use of Gaussian orbitals to speed up molecular electronic structure calculations as opposed to using Slater-type orbitals, a choice made to improve performance on the limited computing capacities of then-current computer hardware for Hartree–Fock calculations. The current version of the program is Gaussian 16. Originally available through the Quantum Chemistry Program Exchange, it was later licensed out of Carnegie Mellon University, and since 1987 has been developed and licensed by Gaussian, Inc. Standard abilities According to the most recent Gaussian manual, the package can do: *Molecular mechanics **AMBER ** Universal force field (UFF) **DREIDING force field *Semi-empirical quantum chemistry method calculations **Aus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NDDO
In computational chemistry, NDDO (neglect of diatomic differential overlap) is a formalism that was first introduced by John Pople; it is the basis for most semiempirical methods. While INDO added all one-centre two electron integrals to the CNDO/2 formalism, NDDO adds all two centre integrals for repulsion between a charge distribution on one centre and a charge distribution on another centre.J. Pople and D. Beveridge, ''Approximate Molecular Orbital Theory'', McGraw-Hill, 1970 Otherwise, the zero-differential overlap approximation is used. The common software program is MOPAC (Molecular Orbital PACkage). In the NDDO method, the overlap matrix ''S'' is replaced by the unit matrix. This allows the Hartree–Fock secular equation , H-ES, = 0 to be replaced with a simpler equation, , H-E, = 0. The two-electron integrals from the NDDO approximation can either be one-, two-, three- or four-centered. The one- and two-centered integrals are evaluated approximately or parameteriz ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MINDO
MINDO, or Modified Intermediate Neglect of Differential Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Intermediate Neglect of Differential Overlap ( INDO) method of John Pople. It was developed by the group of Michael Dewar and was the original method in the MOPAC program. The method should actually be referred to as MINDO/3. It was later replaced by the MNDO MNDO, or Modified Neglect of Diatomic Overlap is a semi-empirical method for the quantum calculation of molecular electronic structure in computational chemistry. It is based on the Neglect of Diatomic Differential Overlap integral approximation. ... method, which in turn was replaced by the PM3 and AM1 methods. References * Semiempirical quantum chemistry methods {{quantum-chemistry-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOPAC
MOPAC is a computational chemistry software package that implements a variety of semi-empirical quantum chemistry methods based on the neglect of diatomic differential overlap (NDDO) approximation and fit primarily for gas-phase thermochemistry. Modern versions of MOPAC support 83 elements of the periodic table (H-La, Lu-Bi as atoms, Ce-Yb as ionic ''sparkles'') and have expanded functionality for solvated molecules, crystalline solids, and proteins. MOPAC was originally developed in Michael Dewar's research group in the early 1980s and released as public domain software on the Quantum Chemistry Program Exchange in 1983. It became commercial software in 1993, developed and distributed by Fujitsu, and Stewart Computational Chemistry took over commercial development and distribution in 2007. In 2022, it was released as open-source software on GitHub. Functionality MOPAC is primarily a serial command-line program. Its default behavior is to take a molecular geometry specifie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computational Chemistry
Computational chemistry is a branch of chemistry that uses computer simulations to assist in solving chemical problems. It uses methods of theoretical chemistry incorporated into computer programs to calculate the structures and properties of molecules, groups of molecules, and solids. The importance of this subject stems from the fact that, with the exception of some relatively recent findings related to the hydrogen molecular ion (dihydrogen cation), achieving an accurate quantum mechanical depiction of chemical systems analytically, or in a closed form, is not feasible. The complexity inherent in the many-body problem exacerbates the challenge of providing detailed descriptions of quantum mechanical systems. While computational results normally complement information obtained by chemical experiments, it can occasionally predict unobserved chemical phenomena. Overview Computational chemistry differs from theoretical chemistry, which involves a mathematical description of chem ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organometallic
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and sometimes broadened to include metalloids like boron, silicon, and selenium, as well. Aside from bonds to organyl fragments or molecules, bonds to 'inorganic' carbon, like carbon monoxide (Metal carbonyl, metal carbonyls), cyanide, or carbide, are generally considered to be organometallic as well. Some related compounds such as transition metal hydrides and metal phosphine complexes are often included in discussions of organometallic compounds, though strictly speaking, they are not necessarily organometallic. The related but distinct term "metalorganics, metalorganic compound" refers to metal-containing compounds lacking direct metal-carbon bonds but which contain organic ligands. Metal β-diketonates, alkoxides, dialkylamides, and metal p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PC GAMESS
Firefly, formerly named PC GAMESS, is an ab initio computational chemistry program for Intel-compatible x86, x86-64 processors based on GAMESS (US) sources. However, it has been mostly rewritten (60-70% of the code), especially in platform-specific parts (memory allocation, disk input/output, network), mathematic functions (e.g., matrix operations), and quantum chemistry methods (such as Hartree–Fock method, Møller–Plesset perturbation theory, and density functional theory). Thus, it is significantly faster than the original GAMESS. The main maintainer of the program was Alex Granovsky. Since October 2008, the project is no longer associated with GAMESS (US) and the Firefly rename occurred. Until October 17, 2009, both names could be used, but thereafter, the package should be referred to as Firefly exclusively. History On December 4, 2009, the support of any PC GAMESS versions earlier than the first PC GAMESS Firefly version 7.1.C was abandoned, and any and all licenses to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
