Showing papers on "Møller–Plesset perturbation theory published in 2008"

Accelerating Resolution-of-the-Identity Second-Order Moller-Plesset Quantum Chemistry Calculations with Graphical Processing Units

Abstract: The modification of a general purpose code for quantum mechanical calculations of molecular properties (Q-Chem) to use a graphical processing unit (GPU) is reported. A 4.3x speedup of the resolution-of-the-identity second-order Moller-Plesset perturbation theory (RI-MP2) execution time is observed in single point energy calculations of linear alkanes. The code modification is accomplished using the compute unified basic linear algebra subprograms (CUBLAS) library for an NVIDIA Quadro FX 5600 graphics card. Furthermore, speedups of other matrix algebra based electronic structure calculations are anticipated as a result of using a similar approach.

Improved supermolecular second order Møller-Plesset intermolecular interaction energies using time-dependent density functional response theory.

Abstract: The supermolecular second order Moller-Plesset (MP2) intermolecular interaction energy is corrected by employing time-dependent density functional (TDDFT) response theory. This is done by replacing the uncoupled second order dispersion contribution contained in the supermolecular MP2 energy with the coupled dispersion energy obtained from the TDDFT approach. Preliminary results for the rare gas dimers He2, Ne2, and Ar2 and a few structures of the (HF)2 and (H2O)2 dimers show that the conventional MP2 interaction energies are considerably improved by this procedure if compared to coupled cluster singles doubles with perturbative triples [CCSD(T)] interaction energies. However, the quality of the interaction energies obtained in this way strongly depends on the exchange-correlation potential employed in the monomer calculations: It is shown that an exact exchange-only potential surprisingly often performs better than an asymptotically corrected hybrid exchange-correlation potential. Therefore the method pro...

Consequences of Spin Contamination in Unrestricted Calculations on Open-Shell Species: Effect of Hartree-Fock and Møller-Plesset Contributions in Hybrid and Double-Hybrid Density Functional Theory Approaches

Abstract: The extent of spin contamination in unrestricted versions of pure, hybrid and double-hybrid density functional theory (DFT) methods, and its consequences, as manifested in the difference between unrestricted and restricted energies (U - R), has been investigated for 22 homolytic bond dissociation reactions. In accordance with previous studies, increasing the amount of Hartree-Fock (HF) exchange in unrestricted hybrid DFT procedures leads to an increase in the extent of spin contamination. However, in unrestricted double-hybrid DFT procedures, which include both a proportion of HF exchange and a perturbative correlation contribution (MP2), the opposing behavior of UHF and UMP2 with respect to spin contamination leads to smaller differences between the energies predicted by unrestricted and restricted variants. For example, for the most spin-contaminated radicals, a 30-100 kJ mol(-1) |U - R| difference at the HF and MP2 levels is reduced to just 0-5 kJ mol(-1) with the double-hybrid functionals. The double-hybrid UDFT procedures can thus benefit from the inclusion of UHF and UMP2 contributions without incurring to the same extent the problems associated with spin contamination.

Eliminating the domain error in local explicitly correlated second-order Møller-Plesset perturbation theory.

Abstract: A new explicitly correlated local MP2-F12 method is proposed in which the error caused by truncating the virtual orbital space to pair-specific local domains is almost entirely removed. This is achieved by a simple modification of the ansatz for the explicitly correlated wave function, which makes it possible that the explicitly correlated terms correct both for the basis set incompleteness error as well as for the domain error in the LMP2. Benchmark calculations are presented for 21 molecules and 16 chemical reactions. The results demonstrate that the local approximations have hardly any effect on the accuracy of the computed correlation energies and reaction energies, and the LMP2-F12 reaction energies agree within 0.1–0.2 kcal/mol with estimated MP2 basis set limits.

Minimax approximation for the decomposition of energy denominators in Laplace-transformed Møller–Plesset perturbation theories

Abstract: We implement the minimax approximation for the decomposition of energy denominators in Laplace-transformed Moller–Plesset perturbation theories. The best approximation is defined by minimizing the Chebyshev norm of the quadrature error. The application to the Laplace-transformed second order perturbation theory clearly shows that the present method is much more accurate than other numerical quadratures. It is also shown that the error in the energy decays almost exponentially with respect to the number of quadrature points.

An atomic orbital-based reformulation of energy gradients in second-order Møller-Plesset perturbation theory.

Abstract: A fully atomic orbital (AO)-based reformulation of second-order Moller–Plesset perturbation theory (MP2) energy gradients is introduced, which provides the basis for reducing the computational scaling with the molecular size from the fifth power to linear Our formulation avoids any transformation between the AO and the molecular orbital (MO) basis and employs pseudodensity matrices similar to the AO-MP2 energy expressions within the Laplace scheme for energies The explicit computation of perturbed one-particle density matrices emerging in the new AO-based gradient expression is avoided by reformulating the Z-vector method of Handy and Schaefer [J Chem Phys 81, 5031 (1984)] within a density matrix-based scheme

Potential energy curve for isomerization of N2H2 and C2H4 using the improved virtual orbital multireference Møller–Plesset perturbation theory

Abstract: Multireference Moller–Plesset (MRMP) perturbation theory [K. Hirao, Chem. Phys. Lett. 190, 374 (1992)] is modified to use improved virtual orbitals (IVOs) and is applied to study ground state potential energy curves for isomerization and dissociation of the N2H2 and C2H4 molecules. In contrast to traditional MRMP or multistate multiconfiguration quasidegenerate perturbation theory where the reference functions are obtained from (often difficult to converge) state averaged multiconfiguration self-consistent field methods, our reference functions are represented in terms of computationally efficient IVOs. For convenience in comparisons with other methods, a first order complete active space configuration interaction (CASCI) calculation with the IVOs is followed by the use of the IVOs in MRMP to incorporate residual electron correlation effects. The potential energy curves calculated from the IVO-MRMP method are compared with computations using state-of-the-art coupled cluster singles and doubles (CCSD) meth...

Calculating stacking interactions in nucleic acid base-pair steps using spin-component scaling and local second order Møller-Plesset perturbation theory.

Abstract: Stacking interaction energies for ten B-DNA base-pair steps are computed with density fitted local second-order Moller–Plesset perturbation theory (DF-LMP2), and with the spin-component scaled (SCS) and spin-component scaled for nucleobases (SCSN) variants of DF-LMP2. Comparison with existing CBS(T) reference data indicates larger than expected energy differences for both SCS variants. After an analysis of the errors involved, an alternative method of producing reference data is proposed where DF-LMP2/aug-cc-pVTZ and DF-LMP2/aug-cc-pVQZ energies for the whole complex are extrapolated to produce interaction energies that do not require many-body correction and show reduced error in estimation of the basis set limit. A literature correction term from coupled cluster theory with perturbative triples is then added to the DF-LMP2 estimated basis set limit. These new reference data are consistently around 1 kcal mol−1 less than previous literature data. DF-SCSN-LMP2/aug-cc-pVTZ is found to reproduce the new reference interaction energies with a root mean square error (RMSE) of 0.71 kcal mol−1, while SCS consistently underestimates the binding energy.

Calculated interactions of a nitro group with aromatic rings of crystalline picryl bromide

Abstract: Several crystalline polymorphs have been discovered for picryl bromide. Among the several forces that control the formation of such polymorphs are the interactions among the nitro groups and phenyl rings of those crystals. Although there are >300 structures to be found in the Cambridge Structural Database displaying the nitro-phenyl interaction, nonetheless this interesting, and apparently important, interaction, seems not to have been discussed within any of the papers reporting the structures. In this article, quantum calculations are reported that assess the strength of these nitro-phenyl interactions within a crystal of picryl bromide. The rather flat molecules of picryl bromide are arranged in layered planes within the crystal, and we examine the attractive interactions that occur within a given plane, and between adjacent planes. Calculations of Hartree Fock and Moller Plesset perturbation theory carried to a second-order expansion are used. Both quantum mechanical approximations are implemented with 6–31G* basis functions.

Calculation of weakly polar interaction energies in polypeptides using density functional and local Møller‐Plesset perturbation theory

Abstract: The interaction energies of ubiquitous weakly polar interactions in proteins are comparable with those of hydrogen bonds, consequently, they stabilize local, secondary, and tertiary structures. However, the most widely-used density functionals fail to describe the weakly polar interactions. Thus, it is important to find and test functionals which adequately describe and quantify the energetics of such interactions. For this purpose, interaction energies in the hydrophobic core of rubredoxin (PDB id: 1rb9) and in the S22 subset of the JSCH-2005 benchmark database were computed with the BHandHLYP and PWPW91 functionals and with the pseudospectral implementation of the local MP2 (PS-LMP2) method. The cc-pVDZ, cc-pVTZ(-f), cc-pVTZ, cc-pVQZ(-g), aug-cc-pVDZ, aug-cc-VTZ(-f), and aug-cc-pVTZ basis sets were used for the calculations. In the S22 subset the PS-LMP2 results were extrapolated to the complete basis set limit. Furthermore, the a posteriori counterpoise method of Boys and Bernardi was used to correct the basis set superposition errors in the calculation of interaction energies. Calculations using the BHandHLYP functional, both for the various weakly polar interactions in rubredoxin and for the dispersion interactions in the S22 subset, were in good agreement with those using the coupled cluster (CCSD(T)) and the resolution of identity MP2 (RIMP2) methods and clearly outperformed both the PWPW91 functional and the PS-LMP2 method. The results for the S22 hydrogen bonded subset, obtained with PWPW91 calculations, were closest to those of the reference high level calculations. For the "mixed" (hydrogen bonded and dispersive) interactions in the S22 subset, results obtained with the BHandHLYP and PS-LMP2 calculations agreed well with the reference calculations.

Assessment of multicoefficient correlation methods, second-order Møller-Plesset perturbation theory, and density functional theory for H3O(+)(H2O)n (n = 1-5) and OH(-)(H2O)n (n = 1-4).

Abstract: We have assessed the ability of 52 methods including 15 multicoefficient correlation methods (MCCMs), two complete basis set (CBS) methods, second-order Moller−Plesset perturbation theory (MP2) with 5 basis sets, the popular B3LYP hybrid functional with 6 basis sets, and 24 combinations of local density functional and basis set to accurately reproduce reaction energies obtained at the Weizmann-1 level of theory for hydronium, hydroxide, and pure water clusters. The three best methods overall are BMC-CCSD, G3SX(MP3), and M06-L/aug-cc-pVTZ. If only microsolvated ion data is included, M06-L/aug-cc-pVTZ is the best method; it has errors only half as large as the other density functionals. The deviations between the three best performing methods are larger for the larger hydronium- and hydroxide-containing clusters, despite a decrease in the average reaction energy, making it impossible to determine which of the three methods is overall the best, so they might be ranked in order of increasing cost, with BMC−CC...

Second-order Møller–Plesset calculations on the water molecule using Gaussian-type orbital and Gaussian-type geminal theory

Abstract: The Gaussian-type orbital and Gaussian-type geminal (GGn) model is applied to the water molecule, at the level of second-order Moller–Plesset (MP2) theory. In GGn theory, correlation factors are attached to all doubly-occupied orbital pairs (GG0), to all doubly-occupied and singly-excited pairs (GG1), or to all orbital pairs (GG2). Optimizing the GG2 model using a weak-orthogonality functional, we obtain the current best estimate of the all-electron MP2 correlation energy of water, −361.95 mEh. In agreement with previous observations, the GG1 model performs almost as well as the GG2 model (−361.26 mEh), whereas the GG0 model is poorer (−351.36 mEh). For the barrier to linearity of water, we obtain an MP2 correlation contribution of −463 ± 5 cm−1.

Energy density analysis for second-order Møller-Plesset perturbation theory and coupled-cluster theory with singles and doubles: application to C2H4--CH4 complexes.

Abstract: Grid-based energy density analysis (EDA), in which numerical integration is performed for two-electron integrals by the pseudospectral method (Imamura et al., J. Chem. Phys. 2007, 126, 034103), is extended to correlated methods: second-order Moller-Plesset (MP2) perturbation and coupled-cluster singles and doubles (CCSD). Using EDA for MP2 and CCSD, we estimate atomic correlation energy differences and correlation energy density difference maps for C2H4CH4 complexes. The analyses confirm that polarization and diffuse functions essentially contribute to the descriptions of weak interaction around the nuclei and in the area between C2H4 and CH4, respectively. © 2008 Wiley Periodicals, Inc. J Comput Chem 29: 1555–1563, 2008

Natural bond orbital‐based energy density analysis for correlated methods: Second‐order Møller–Plesset perturbation and coupled‐cluster singles and doubles

Abstract: Natural bond orbital-based energy density analysis (NBO-EDA), which split energies into atomic and bonding contributions, is proposed for correlated methods such as coupled-cluster singles and doubles (CCSD) and second-order Moller–Plesset (MP2) perturbation. Applying NBO-EDA for CCSD and MP2 to ethylene and the Diels–Alder reaction, we are successful in obtaining useful knowledge regarding electron correlation of π- and σ-type orbitals, and clarifying the difference of the reaction barriers and heat of reaction calculated by CCSD and MP2. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008

Improved virtual orbital multireference Møller-Plesset study of the ground and excited electronic states of protonated acetylene, C2H3+.

Abstract: The ground state geometries and associated normal mode frequencies of the classical and nonclassical protonated acetylene ion, i.e., the vinyl cation C(2)H(3) (+), are computed using the complete active space self-consistent field and improved virtual orbital (IVO) complete active space configuration interaction methods. In addition, the minimum-energy reaction path for the classical to nonclassical interconversion is determined (as are excitation energies) using the IVO modification of multireference Moller-Plesset (MRMP) perturbation theory. The IVO-MRMP treatment predicts the nonclassical structure to be 4.8 kcalmol more stable than the classical one, which is consistent with other high level theoretical estimates. The proton affinity of acetylene from the IVO-MRMP treatment (154.8 kcalmol) also agrees well with experiment (153.3 kcalmol) and with earlier CASPT2 calculations (154.8 kcalmol). We further report geometries and vibrational frequencies of low lying excited states of C(2)H(3) (+), which have not been observed and/or studied before. Comparisons with previous highly correlated calculations further demonstrate the computational efficiency of the IVO-MRPT methods.

Conformational and vibrational analysis of 2-, 3- and 4-trifluoromethylbenzaldehyde by ab initio Hartree–Fock, density functional theory and Moller–Plesset pertubasyon theory calculations

Abstract: The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments of the two planar O-cis and O-trans rotomers of 2-, 3- and 4-trifluoromethylbenzaldehydes have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-311++G(d,p) basis set level. The calculations were adapted to the Cs symmetries of all the molecules. The O-trans rotomers with lower energy of all the compounds have been found as preferential rotomers in the ground state. The mean vibrational deviations between the calculated vibrational frequency values of the two conformers of all the compounds have been shown to increase while the relative energies increase, and so it has been concluded that the higher the relative energy between the two conformers the bigger is the mean vibrational deviation. It has also been found that HF method is superior to B3LYP for the geometric parameters and vibrational frequencies. For comparison electron correlation effect the geometries have also been optimized using Moller-Plesset (MP2) theory with 6-311++G(d,p) basis set level. The energies and bond lengths calculated at MP2 level are found to be slightly bigger than those calculated at HF level. This was attributed that the inclusion of the electron correlation effect causes the bond lengths more close to the experimental values. © 2008 Elsevier B. V. All rights reserved.

A Comparison of Møller-Plesset and Coupled Cluster Linear Response Theory Methods for the Calculation of Dipole Oscillator Strength Sum Rules and C6 Dispersion Coefficients

Abstract: Four correlated linear response theory methods - the second order polarization propagator approximation (SOPPA), the second order polarization propagator approximation with coupled cluster singles and doubles amplitudes, SOPPA(CCSD), the CC2 and coupled cluster singles doubles (CCSD) linear response theory - were used to determine the dipole oscillator strength sum rules of the hydrogen halides HX (with X = F, Cl, Br and I) and the C 6 dispersion coefficient for all pairs of interacting HX molecules via numerical integration of the Casimir-Polder formula. The dependence of the polarizabilities, their frequency dependence and the C 6 coefficients on the level of correlation and the dependence of the C 6 coefficients on the two intramolecular bond lengths were studied.

From exact-WKB toward singular quantum perturbation theory II

Abstract: Following earlier studies, several new features of singular perturbation theory for one-dimensional quantum anharmonic oscillators are computed by exact WKB analysis; former results are thus validated.

Modeling intercalation through the sandwich‐type interactions between benzene and 14 polyaromatic molecules: DFT and ab initio results

Abstract: We use second order Moller Plesset perturbation theory and several density functional theory methods to calculate the counterpoise corrected electronic interaction energies between benzene and a series of polyaromatic molecules. These systems serve as a simple model for DNA intercalation. We show that addition of nitrogen atoms to the polyaromatic molecules always increases sandwich-type interactions, and that, of the density functional theory methods studied, only SVWN can mimic the interaction energies and optimal separations obtained with perturbation theory. SVWN reproduces the optimal molecular distances obtained with perturbation theory very well, and often comes within less than 10% of the interaction energy. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008