General atomic and molecular electronic structure system (2025)

Recent developments in the general atomic and molecular electronic structure system

Journal of Chemical Physics, 2020

A discussion of many of the recently implemented features of GAMESS (General Atomic and Molecular Electronic Structure System) and LibCChem (the C++ CPU/GPU library associated with GAMESS) is presented. These features include fragmentation methods like the fragment molecular orbital, effective fragment potential and effective fragment molecular orbital methods, hybrid MPI/OpenMP approaches to Hartree-Fock and resolution of the identity second order perturbation theory. Many new coupled cluster theory methods have been implemented in GAMESS, as have multiple levels of density functional/tight binding theory. The role of accelerators, especially graphical processing units, is discussed in the context of the new features of LibCChem, as is the associated problem of power consumption as the power of computers increases dramatically. The process by which a complex program suite like GAMESS is maintained and developed is considered. Future developments are briefly summarized. I. Overview/Background GAMESS (General Atomic and Molecular Electronic Structure System) was originally developed by Dupuis and co-workers in the late 1970s under the auspices of the National Resource for Computational Chemistry (NRCC), an organization that was sponsored by the National Science Foundation. GAMESS is a multi-functional electronic structure program with users in more than 100 countries and is run on nearly every available architecture, ranging from MacOS and Windows to the pre-exascale system Summit at Oak Ridge National Laboratory. GAMESS is a "cousin" of the HONDO program which continues to be

Generalised Atomic and Molecular Electronic Structure System

Molecular Modeling and Electronic Structure Calculations

2017

This laboratory is designed to use the program GAMESS (General Atomic Molecular Electronic Structure System, developed in Gordon research group at Iowa State) through a website called nanoHUB (www.nanoHUB.org) to determine the geometric and electronic properties of numerous small molecules. GAMESS uses ab initio and semi-empirical calculations to determine these properties. Ab initio (“from first principles”) calculations solve the Schrödinger equation using the exact computational expression for the energy of the electrons. The particular ab initio method that we will use for this lab is called HartreeFock (HF). HF uses an approximate wavefunction to solve Schrödinger, so the resulting molecular properties are approximate, but for many applications the accuracy is adequate for interpreting experiments. Semi-empirical calculations use an approximate energy expression for the electrons, but solve for the exact wavefunction associated with this expression. Usually the energy expressio...

Journal of Molecular Structure

Synthesis, spectral analysis (FT-IR, 1 HNMR, 13 CNMR and UV-visible) and quantum chemical studies on molecular geometry, NBO, NLO, chemical reactivity and thermodynamic properties of novel 2-Synthesis, spectral analysis (FT-IR, 1 HNMR, 13 CNMR and UV-visible) and quantum chemical studies on molecular geometry, NBO, NLO, chemical reactivity and thermodynamic properties of novel 2-amino-4-(4-(dimethylamino)phenyl)-5-oxo-6-phenyl-5,6-dihydro-4Hpyrano[3,2-c]quinoline-3-carbonitrile, Journal of Molecular Structure (2015), doi: http://dx.

Understanding the bulk electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Ca</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="...

Physical Review B, 2006

We investigate the electronic structure of Ca1−xSrxVO3 using careful state-of-the-art experiments and calculations. Photoemission spectra using synchrotron radiation reveal a hitherto unnoticed polarization dependence of the photoemission matrix elements for the surface component leading to a substantial suppression of its intensity. Bulk spectra extracted with the help of experimentally determined electron escape depth and estimated suppression of surface contributions resolve outstanding puzzles concerning the electronic structure in Ca1−xSrxVO3.

Theoretical study of structural and electronic properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">VH</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

Physical review, 1998

We have calculated the change in the electronic structure and the distortion of the lattice in vanadium upon hydrogenation from first principles using the full-potential linear muffin-tin-orbital method and the linear augmented plane-wave method in the local-density approximation. The calculated hydrogen induced volume expansions agree with experiment and the change in the c/a ratio is also in good agreement with observations where such are available for single phase VH x. Among several changes in the electronic structure, we note a hybridization of the d band of vanadium with the hydrogen 1s band. We also observe an antiferromagnetically ordered moment at V/V exp ϭ1.08. The possibility of producing magnetic V by means of hydrogenation in combination with epitaxial growth is suggested. ͓S0163-1829͑98͒05433-2͔

PSI3: An open-sourceAb Initio electronic structure package

Journal of Computational Chemistry, 2007

PSI3 is a program system and development platform for ab initio molecular electronic structure computations. The package includes mature programming interfaces for parsing user input, accessing commonly used data such as basis-set information or molecular orbital coefficients, and retrieving and storing binary data (with no software limitations on file sizes or file-system-sizes), especially multi-index quantities such as electron repulsion integrals. This platform is useful for the rapid implementation of both standard quantum chemical methods, as well as the development of new models. Features that have already been implemented include Hartree-Fock, multiconfigurational self-consistentfield, second-order Møller-Plesset perturbation theory, coupled cluster, and configuration interaction wave functions. Distinctive capabilities include the ability to employ Gaussian basis functions with arbitrary angular momentum levels; linear R12 second-order perturbation theory; coupled cluster frequency-dependent response properties, including dipole polarizabilities and optical rotation; and diagonal Born-Oppenheimer corrections with correlated wave functions. This article describes the programming infrastructure and main features of the package. PSI3 is available free of charge through the open-source, GNU General Public License.

Psi4 1.1: An Open-Source Electronic Structure Program Emphasizing Automation, Advanced Libraries, and Interoperability

Journal of chemical theory and computation, 2017

Psi4 is an ab initio electronic structure program providing methods such as Hartree-Fock, density functional theory, configuration interaction, and coupled-cluster theory. The 1.1 release represents a major update meant to automate complex tasks, such as geometry optimization using complete-basis-set extrapolation or focal-point methods. Conversion of the top-level code to a Python module means that Psi4 can now be used in complex workflows alongside other Python tools. Several new features have been added with the aid of libraries providing easy access to techniques such as density fitting, Cholesky decomposition, and Laplace denominators. The build system has been completely rewritten to simplify interoperability with independent, reusable software components for quantum chemistry. Finally, a wide range of new theoretical methods and analyses have been added to the code base, including functional-group and open-shell symmetry adapted perturbation theory (F-SAPT and O-SAPT), densit...

Janus-AT bases: Synthesis, self-assembly, and solid state structures

The Journal of Organic …, 2007

Position 38.03 mm 2θ max 44.9 o No. of Reflections Measured Total: 71210 Unique: 6772 (R int = 0.077) Corrections Absorption (T min = 0.878, T max = 0.990) Lorentz-polarization S29 C. Structure Solution and Refinement Structure Solution Direct Methods (SIR92) Refinement Full-matrix least-squares on F 2 Function Minimized Σ w (Fo 2-Fc 2) 2 Least Squares Weights w=1/(σ 2 (Fo 2)+(0.0871P) 2 +8.3126P) Anomalous Dispersion All non-hydrogen atoms No. Observations (I>0.00σ(I)) 6772 No. Variables 805 Reflection/Parameter Ratio 8.41 Residuals (refined on F 2 , all data): R1; wR2 0.110; 0.185 Goodness of Fit Indicator 1.03 No. Observations (I>2.00σ(I)) 4285 Residuals (refined on F): R1; wR2 0.062; 0.155 Max Shift/Error in Final Cycle 0.00 Maximum peak in Final Diff. Map 0.88 e-/Å 3 Minimum peak in Final Diff. Map-0.38 e-/Å 3

The GAMESS-UK electronic structure package: algorithms, developments and applications

Molecular Physics, 2005

A description of the ab initio quantum chemistry package GAMESS-UK is presented. The package offers a wide range of quantum mechanical wavefunctions, capable of treating systems ranging from closed-shell molecules through to the species involved in complex reaction mechanisms. The availability of a wide variety of correlation methods provides the necessary functionality to tackle a number of chemically important tasks, ranging from geometry optimization and transition-state location to the treatment of solvation effects and the prediction of excited state spectra. With the availability of relativistic ECPs and the development of ZORA, such calculations may be performed on the entire Periodic including the lanthanides. Emphasis is given to the DFT module, which has been extensively developed in recent years, and a number of other, novel features of the program. The parallelization strategy used in the program is outlined, and detailed speedup results are given. Applications of the code in the areas of enzyme and zeolite catalysis and in spectroscopy are described.