Spartan (chemistry software)

Spartan is a molecular modelling and computational chemistry application from Wavefunction. It contains code for molecular mechanics, semi-empirical methods, ab initio models, density functional models, post-Hartree–Fock models, thermochemical recipes including G3(MP2) and T1, and machine learning models like corrected MMFF and Est. Density Functional. Quantum chemistry calculations in Spartan are powered by Q-Chem. Primary functions are to supply information about structures, relative stabilities and other properties of isolated molecules. Molecular mechanics calculations on complex molecules are common in the chemical community. Quantum chemical calculations, including Hartree–Fock method molecular orbital calculations, but especially calculations that include electronic correlation, are more time-consuming in comparison. Quantum chemical calculations are also called upon to furnish information about mechanisms and product distributions of chemical reactions, either directly by calculations on transition states, or based on Hammond's postulate, by modeling the steric and electronic demands of the reactants. Quantitative calculations, leading directly to information about the geometries of transition states, and about reaction mechanisms in general, are increasingly common, while qualitative models are still needed for systems that are too large to be subjected to more rigorous treatments. Quantum chemical calculations can supply information to complement existing experimental data or replace it altogether, for example, atomic charges for quantitative structure-activity relationship (QSAR) analyses, and intermolecular potentials for molecular mechanics and molecular dynamics calculations. Spartan applies computational chemistry methods (theoretical models) to many standard tasks that provide calculated data applicable to the determination of molecular shape conformation, structure (equilibrium and transition state geometry), NMR, IR, Raman, and UV-visible spectra, molecular (and atomic) properties, reactivity, and selectivity.

Computational abilities This software provides the molecular mechanics, Merck Molecular Force Field (MMFF), (for validation test suite), MMFF with extensions, and SYBYL, force fields calculation, Semi-empirical calculations, MNDO/MNDO(D), Austin Model 1 (AM1), PM3, Recife Model 1 (RM1) PM6.

Hartree–Fock, self-consistent field (SCF) methods, available with implicit solvent (SM8). Restricted, unrestricted, and restricted open-shell Hartree–Fock Density functional theory (DFT) methods, available with implicit solvent (SM8). Standard functionals: BP, BLYP, B3LYP, EDF1, EDF2, M06, ωB97X-D

Exchange functionals: HF, Slater-Dirac, Becke88, Gill96, GG99, B(EDF1), PW91 Correlation functionals: VWN, LYP, PW91, P86, PZ81, PBE. Combination or hybrid functionals: B3PW91, B3LYP, B3LYP5, EDF1, EDF2, BMK Truhlar group functionals: M05, M05-2X, M06, M06-L M06-2X, M06-HF Head-Gordon group functionals: ωB97, ωB97X, ωB97X-D Coupled cluster methods. CCSD, CCSD(T), CCSD(2), OD, OD(T), OD(2), QCCD, VOD, VOD(2), VQCCD Møller–Plesset methods. MP2, MP3, MP4, RI-MP2 Excited state methods. Time-dependent density functional theory (TDDFT) Configuration interaction: CIS, CIS(D), QCIS(D), quadratic configuration interaction (QCISD(T)), RI-CIS(D) Quantum chemistry composite methods, thermochemical recipes. T1, G2, G3, G3(MP2)

Tasks performed Available computational models provide molecular, thermodynamic, QSAR, atomic, graphical, and spectral properties. A calculation dialogue provides access to the following computational tasks:

Energy – For a given geometry, provides energy and associated properties of a molecule or system. If quantum chemical models are employed, the wave function is calculated. Equilibrium molecular geometry - Locates the nearest local minimum and provides energy and associated properties. Transition state geometry - Locates the nearest first-order saddle point (a maximum in a single dimension and minima in all others) and provides energy and associated properties. Equilibrium conformer – Locates lowest-energy conformation. Often performed before calculating structure using a quantum chemical model. Conformer distribution – Obtains a selection of low-energy conformers. Commonly used to identify the shapes a specific molecule is likely to adopt and to determine a Boltzmann distribution for calculating average molecular properties. Conformer library – Locates lowest-energy conformer and associates this with a set of conformers spanning all shapes accessible to the molecule without regard to energy. Used to build libraries for similarity analysis. Energy profile – Steps a molecule or system through a user defined coordinate set, providing equilibrium geometries for each step (subject to user-specified constraints). Similarity analysis – quantifies the likeness of molecules (and optionally their conformers) based on either structure or chemical function (Hydrogen bond acceptors–donors, positive–negative ionizables, hydrophobes, aromatics). Quantifies likeness of a molecule (and optionally its conformers) to a pharmacophore.

Graphical user interface The software contains an integrated graphical user interface. Touch screen operations are supported for Windows 7 and 8 devices. Construction of molecules in 3D is facilitated with molecule builders (included are organic, inorganic, peptide, nucleotide, and substituent builders). 2D construction is supported for organic molecules with a 2D sketch palette. The Windows version interface can access ChemDraw; which versions 9.0 or later may also be used for molecule building in 2D. A calculations dialogue is used for specification of task and computational method. Data from calculations are displayed in dialogues, or as text output. Additional data analysis, including linear regression, is possible from an internal spreadsheet.

Graphical models

Graphical models, especially molecular orbitals, electron density, and electrostatic potential maps, are a routine means of molecular visualization in chemistry education.

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