An Ab Initio Pseudopotential Study of MnPo (M = Cu, Ag, Au; n = 1, 2) Systems

2005 ◽  
Vol 58 (11) ◽  
pp. 792 ◽  
Author(s):  
Qi-Mu Surong ◽  
Yongfang Zhao ◽  
Xiaogong Jing ◽  
Fengli Liu ◽  
Xinying Li ◽  
...  
Keyword(s):  
Bond Length ◽  
Electron Correlation ◽  
Bond Angle ◽  
Relativistic Effects ◽  
Cluster Method ◽  
Coinage Metal ◽  
Hartree Fock ◽  
Electron Correlation Effects ◽  
Moller Plesset ◽  
Correlation Corrections

The small coinage-metal polonium compounds MPo and M2Po, (M = Cu, Ag, Au) are studied at Hartree–Fock (HF), second-order Møller–Plesset perturbation theory (MP2), and coupled cluster method CCSD(T) levels using relativistic and non-relativistic pseudopotentials. The calculated geometries indicate that the M2Po (M = Cu, Ag, Au) systems have bent structures of ~64° angles. Electron correlation corrections to the bond length M–Po are extremely small, but to the bond angle M–Po–M are significant; in general, it was reduced from 86° to 64°. Relativistic effects on bond angle are small, but on bond length are distinct. Both electron correlation effects and relativistic effects are essential to determine the geometry and relative stability of the systems. It can be predicted that Au2Po is relatively stable compared with Ag2Po.

scholarly journals Ab Initio Simulation of the IR Spectrum of Hydrated Kaolinite

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1146
Author(s):  
Victor Yavna ◽  
Tatiana Nazdracheva ◽  
Andrey Morozov ◽  
Yakov Ermolov ◽  
Andrei Kochur
Keyword(s):  
Ir Spectrum ◽  
Cluster Method ◽  
Water Molecules ◽  
Ab Initio Simulation ◽  
Theoretical Methods ◽  
Hartree Fock ◽  
Wave Numbers ◽  
Adsorption Energies ◽  
Moller Plesset ◽  
Correlation Corrections

The hydration of the basal surfaces of kaolinite is studied by theoretical methods. The cluster method was used to simulate the positions of atoms. The positions of the atoms of the basal surfaces of dry and hydrated minerals are optimized by minimizing the total energy in the Hartree–Fock approximation. The adsorption energies of water molecules were calculated taking into account the fourth-order correlation corrections of Møller–Plesset perturbation theory. The formation of the IR spectrum of kaolinite in the range of wave numbers 2500–4500 cm−1 is studied. The experimentally observed effect of the change in relative intensity and position of the band with a change in the moisture content of the sample is interpreted.

Energy spectra of the tungsten ion 4s24pN, 4s24N–14d and 4s4pN+1 configurations

2015 ◽  
Vol 55 (3) ◽  
Author(s):  
Pavel Bogdanovich ◽  
Rasa Karpuškienė ◽  
Romualdas Kisielius
Keyword(s):  
Energy Level ◽  
Configuration Interaction ◽  
Electron Correlation ◽  
Relativistic Effects ◽  
Energy Spectra ◽  
Correlation Effects ◽  
Interaction Method ◽  
Configuration Interaction Method ◽  
Hartree Fock ◽  
Electron Correlation Effects

The ab initio quasirelativistic Hartree–Fock approximation was used to determine spectroscopic parameters for the multicharged tungsten ions with an open 4p shell. The configuration interaction method based on the transformed radial orbitals was applied to include the electron-correlation effects. The relativistic effects were taken into account in the Breit–Pauli approximation for the quasirelativistic Hartree–Fock radial orbitals. The complete energy level spectra were calculated for the 4s24pN, 4s24pN–14d and 4s4pN+1 configurations of the tungsten ions from W43+ to W38+.

Ab Initio Study of Structure and Stability of M2Al2 (M = Cu, Ag, and Au) Clusters

2007 ◽  
Vol 60 (3) ◽  
pp. 184 ◽  
Author(s):  
FengLi Liu ◽  
YongFang Zhao ◽  
XinYing Li ◽  
FengYou Hao
Keyword(s):  
Molecular Orbital ◽  
Relativistic Effects ◽  
Binding Energies ◽  
Present Species ◽  
Coinage Metal ◽  
Hartree Fock ◽  
Au Clusters ◽  
Highest Occupied Molecular Orbital ◽  
Lowest Unoccupied Molecular Orbital ◽  
Moller Plesset

Coinage metal aluminium clusters M2Al2 (M = Cu, Ag, and Au) were studied by Hartree–Fock (HF) and second-order Møller–Plesset perturbation theory (MP2) with pseudopotentials. It was found that the butterfly structure with C2v (1A1) symmetry is more stable than the planar structure, and Au2Al2 is the most stable of the title species. The binding energies and the highest occupied molecular orbital and the lowest unoccupied molecular orbital (HOMO–LUMO) gap are evaluated, which indicates that doping clusters M2Al2 are more stable than the pure clusters M4 (M = Cu, Ag, and Au). Electron correlation and relativistic effects stabilize the present species.

Relativistic and Electron Correlation Effects as a Tool for Explaining Some Trends in Molecular Properties and Interactions

2006 ◽  
Vol 1 (1) ◽  
pp. 259-265 ◽  
Author(s):  
Miroslav Urban ◽  
Vladimír Kellö
Keyword(s):  
Electron Affinity ◽  
Electron Correlation ◽  
Heavy Atom ◽  
Lone Pair ◽  
Relativistic Effects ◽  
Electric Properties ◽  
Molecular Properties ◽  
Cluster Method ◽  
Correlation Effects ◽  
Electron Correlation Effects

In this paper we discuss relatively routine Douglas–Kroll–Hess spin–free relativistic calculations as a tool for understanding some trends of molecular properties within the series of related molecules. Electron correlation effects are considered by the Coupled Cluster method with iterative treatment of the single and double excitation operators and perturbative treatment of triples, CCSD(T). For our analysis we use accumulated data on relativistic effects on ionization potentials, electron affinities and polarizabilities of the coinage elements, Cu, Ag, and Au and related series like Ia and IIa group elements. Next we analyze electric properties of diatomic molecules as CuF, AgF, and AuF, and compare electric properties and bonding energies of these molecules with intermetalics CuAl, AgAl, AuAl. Electric dipole moments and dipole polarizabilities of the series of oxides including a heavy atom, GeO, SnO, and PbO in their 1∑ ground states are also analyzed. Particular attention is paid to the dissociation energy of PbO and its electron affinity. The bonding character of the MeL series of complexes (Me=Cu, Ag, Au; L=H2O, NH3, and H2S) is explained by stressing the importance of the charge transfer from the lone pair of the ligand to the metal element. Relativistic effects which affect the Me electron affinity and polarizability facilitate understanding the trends of Me interactions with different ligands. We also mention using of the optimized virtual orbital space (OVOS) as an instrument which allows to circumvent problems with proper contraction needed for a specific approximate relativistic Hamiltonian. OVOS allows to reduce the computer time of correlated relativistic calculation by an order of magnitude.

Quantifying electron-correlation effects in small coinage-metal clusters by ab initio calculations

2021 ◽  
Author(s):  
Victor Giovanni de Pina ◽  
Bráulio Gabriel Alencar Brito ◽  
Guo -Q Hai ◽  
Ladir Cândido
Keyword(s):  
Monte Carlo ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Metal Clusters ◽  
Correlation Effects ◽  
Diffusion Monte Carlo ◽  
Coinage Metal ◽  
Electron Correlation Effects ◽  
Fixed Node

We investigate many-electron correlation effects in neutral and charged coinage-metal clusters Cun, Agn, and Aun (n = 1 − 4) by ab initio calculations using fixed-node diffusion Monte Carlo (FN-DMC)...

The structures and stabilities of singlet and triplet dithiatriazines: a computational study

1988 ◽  
Vol 66 (9) ◽  
pp. 2279-2284 ◽  
Author(s):  
R. E. Hoffmeyer ◽  
W.-T. Chan ◽  
J. D. Goddard ◽  
R. T. Oakley
Keyword(s):  
Excited States ◽  
Electron Correlation ◽  
Computational Study ◽  
Geometry Optimization ◽  
Hartree Fock ◽  
Structural Distortions ◽  
Energy Gaps ◽  
Jahn Teller ◽  
Moller Plesset ◽  
Triplet Excited States

Ab initio molecular orbital and Møller–Plesset perturbation theory calculations have been carried out on two model dithiatriazines RCN3S2 (R = H, NH2). With geometry optimization and the inclusion of electron correlation both of these dithiatriazines are predicted to be ground state singlets. Both molecules have low-lying triplet excited states, with energy gaps of 6.6 (R = H) and 13.0 (R = NH2) kcal mol−1. The singlet dithiatriazines distort from high (C2v) to low (Cs) symmetry, and these changes are important in determining the relative energies of the singlet and triplet molecules. The structural distortions experienced by these molecules are related to Hartree–Fock and Jahn–Teller instabilities in other thiazene heterocycles.

Electron correlation and relativistic effects in the coinage metal compounds.

1995 ◽  
Vol 92 (4) ◽  
pp. 253 ◽  
Author(s):  
Vladimir Kellö ◽  
Andrzej J. Sadlej
Keyword(s):  
Electron Correlation ◽  
Relativistic Effects ◽  
Metal Compounds ◽  
Coinage Metal

The 1,2,3,5-ditelluradiazolyl [HCN2Te2] species. Theoretical characterizations of the cation, radical, and radical dimers

1996 ◽  
Vol 74 (6) ◽  
pp. 810-818 ◽  
Author(s):  
William M. Davis ◽  
John D. Goddard
Keyword(s):  
Ab Initio ◽  
Electron Correlation ◽  
Cation Radical ◽  
Building Blocks ◽  
Molecular Conductors ◽  
Face To Face ◽  
Hartree Fock ◽  
Symmetry Constraints ◽  
Moller Plesset ◽  
Low Dimensional

Dithia- and diselena-diazolyl radicals (HCN2E2 E = S, Se) and dimers are important building blocks in the design of low-dimensional molecular conductors. Research on the tellurium-based analogues is much rarer. This work reports the molecular and electronic structures of the cation, radical, and radical dimers of 1,2,3,5-ditelluradiazolyl using ab initio theory including electron correlation by Møller–Plesset perturbation theory up to partial fourth order (MP4SDQ). A face-to-face C2v dimer is predicted to be bound with respect to two radicals by approximately 18 kcal/mol. A C2h, dimer also has been studied and is ca. 2 kcal/mol less stable than the C2v conformer. Relaxing symmetry constraints on the dimers led to more energetically stable structures at the Hartree–Fock level but the C2v structure remains the most stable at a level of theory including electron correlation effects. The results for the Te compounds along with our earlier research on the S and Se analogues provide predictions for the geometries, vibrational frequencies, and ionization potentials for the Te species to assist in future experiments. Key words: tellurium, ab initio, ditelluradiazolyl, dimers, binding.

Calculations of Perovskite Surface Relaxation

2000 ◽  
Vol 654 ◽  
Author(s):  
E. Heifets ◽  
E.A. Kotominc ◽  
R.I. Eglitisc ◽  
R.E. Cohen
Keyword(s):  
Thin Films ◽  
Surface Energy ◽  
Ab Initio ◽  
Shell Model ◽  
Electron Correlation ◽  
Surface Relaxation ◽  
Hartree Fock ◽  
Semi Empirical ◽  
Good Agreement ◽  
Correlation Corrections

AbstractThe (100) and (110) surface relaxations are calculated for SrTiO3 and BaTiO3 perovskite thin films by means of a semi-empirical shell model (SM) for different surface terminations. Our SM results for the (100) surface structure are in good agreement with our present ab initio Hartree-Fock calculations with electron correlation corrections, previous ab initio pseudopotential calculationsand LEED experiments. The surface energy for the Ba-, Sr-, TiO- terminated (110) surfaces is found much larger than that for the (100) one. In contrast, the surface energy for the asymmetric O-termination, where outermost O atoms are strongly on-plane displaced, is the lowest for all (110) terminations and thus the most stable.

Calculation of Second- and Higher-Order Force Constants Including Electron Correlation Effects and Hartree-Fock Force Constant Scaling

2003 ◽  
Vol 44 (4) ◽  
pp. 538-545
Author(s):  
B. K. Novosadov ◽  
Yu. I. Tarasov ◽  
D. M. Kovtun ◽  
I. V. Kochikov
Keyword(s):  
Force Constant ◽  
Electron Correlation ◽  
Higher Order ◽  
Force Constants ◽  
Correlation Effects ◽  
Hartree Fock ◽  
Electron Correlation Effects
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