The Ground State Potential for the Chromium Dimer Revisited

2003 ◽  
Vol 68 (2) ◽  
pp. 265-274 ◽  
Author(s):  
Björn O. Roos
Keyword(s):  
Ground State ◽  
Theoretical Study ◽  
Relativistic Effects ◽  
Basis Set ◽  
Spectroscopic Constants ◽  
Natural Orbital ◽  
State Potential ◽  
Experimental Values ◽  
Atomic Natural Orbital ◽  
Caspt2 Calculations

Results are presented from a new theoretical study of the ground state potential curve of the chromium dimer using multiconfiguration second-order perturbation theory. A new basis set of the atomic natural orbital type is used where the construction includes correlation of the semi-core 3p orbitals and scalar relativistic effects are added using the Douglas-Kroll Hamiltonian. The active space used in the CASSCF/CASPT2 calculations comprised 16 orbitals with 12 active electrons. The resulting ground state potential is in agreement with experiment. Computed spectroscopic constants are (with experimental values within parentheses): Re = 1.66 (1.68) Å, D0 = 1.65 (1.53 ± 0.06) eV, ∆G1/2 = 413 (452) cm-1. Higher vibrational frequencies are also well reproduced.

A CASSCF/CASPT2 STUDY ON THE LOW-LYING ELECTRONIC STATES OF THE (CH3)2CHS AND ITS CATION

2013 ◽  
Vol 12 (06) ◽  
pp. 1350047
Author(s):  
FAN-XIA WANG ◽  
ZENG-XIA ZHAO ◽  
HONG-XING ZHANG
Keyword(s):  
Ground State ◽  
Spectroscopic Data ◽  
Geometry Optimization ◽  
Electronic States ◽  
Vibrational Frequencies ◽  
Geometric Parameters ◽  
Basis Set ◽  
Natural Orbital ◽  
Atomic Natural Orbital ◽  
Good Agreement

The multireference approach (CASSCF/CASPT2) combined with the contracted with atomic natural orbital (ANO-RCC-VTZP) basis set has been used to investigate systematically, the low-lying electronic states of ( CH 3)2 CHS in Cs symmetry. The result of geometry optimization using CASSCF/ANO-RCC-VTZP shows that the theoretically determined geometric parameters and harmonic vibrational frequencies for the ground state X2A′ of ( CH 3)2 CHS are in good agreement with previous studies. In addition, we also explored several cationic states adiabatically and found that the 11A′ state of ( CH 3)2 CHS + is unstable and converts to ( CH 3)2 CSH +. The vertical and adiabatic ionization energies were obtained to compare with photoelectron spectroscopic data.

Electron Affinities of BN, NO and NF: Coupled Cluster and Multireference Configuration Interaction Calculations

2005 ◽  
Vol 70 (7) ◽  
pp. 923-940 ◽  
Author(s):  
Jiří Fišer ◽  
Rudolf Polák
Keyword(s):  
Configuration Interaction ◽  
Relativistic Effects ◽  
Basis Set ◽  
Basis Sets ◽  
Spectroscopic Constants ◽  
Coupled Cluster ◽  
Electron Affinities ◽  
Complete Basis Set ◽  
Correlation Consistent ◽  
Consistent Basis

The accurate adiabatic electron affinities (EA) of the BN, NO and NF molecules have been determined using the coupled cluster approach and multireference configuration interaction methods. By combining large doubly augmented correlation-consistent basis sets (through the sextuple zeta) and complete basis set extrapolations with corrections for core-valence correlation and relativistic effects, we find that the RCCSD(T) method gives EA(BN) = 3.153 eV in very close agreement with experiment and predicts EA(NF) = 0.247 eV. The RCCSD(T) and UCCSD(T) EA(NO) results, 0.008 and 0.031 eV, bracket the experimental value. For both the neutral and anionic ground state species the usual spectroscopic constants were derived.

Theoretical studies on the absorption and luminescent properties of a series of derivatives of 1,3-diphenyl-5-pyrene-2-yl-4,5-dihydro-1H-pyrazole

2005 ◽  
Vol 83 (2) ◽  
pp. 166-173 ◽  
Author(s):  
Xiao-Juan Liu ◽  
Ji-Kang Feng ◽  
Ai-Min Ren ◽  
Xin Zhou ◽  
Hong Cheng
Keyword(s):  
Ground State ◽  
Emission Spectra ◽  
Luminescent Properties ◽  
Basis Set ◽  
Basis Sets ◽  
Absorption And Emission ◽  
Reaction Field ◽  
Hartree Fock ◽  
Polarized Continuum Model ◽  
Experimental Values

The absorption and emission spectra for a series of substituted 1,3-diphenyl-5-pyrene-2-yl-4,5-dihydro-1H-pyrazole (DPPyP) molecules are computed by TDDFT methods. The solvent effect is modeled using the self-consistent reaction field (SCRF) method with Tomasi's polarized continuum model (PCM). The ground-state geometries were optimized by the Hartree–Fock method with the 6-31G basis set (and also with 3-21G* for molecule A) (HF/6-31G), and the lowest singlet excited-state geometries were optimized at the ab initio CIS level with the 6-31G basis set (CIS/6-31G). The calculated results indicate that the TDDFT method can reproduce the experimental values. We consider the effects of different basis sets on the optimization of the ground-state geometries. Specially, some insights on the differences observed for these compounds in changing the substituted donors (H, CH3, and NH2) and acceptor group (CN) are given; the results indicate that introduction of the donor groups will lead emission to be red-shifted, while introduction of the acceptor will induce the emission to be blue-shifted, which provides useful information for modulating light-emitting material colors.Key words: absorption and emission, TDDFT, CIS, SCRF–PCM.

Saddle-point geometries and barriers to internal rotation of formamide : an ab initio study

1980 ◽  
Vol 33 (2) ◽  
pp. 249 ◽  
Author(s):  
L Radom ◽  
NV Riggs
Keyword(s):  
Transition State ◽  
Ground State ◽  
Energy Surface ◽  
Saddle Points ◽  
Geometry Optimization ◽  
Internal Motion ◽  
Basis Set ◽  
Minimal Basis ◽  
Experimental Values ◽  
Extended Basis

By use of a direct transition-state program and the STO-3G minimal basis set, two saddle-points are detected on the energy surface for internal motion of formamide. These correspond mainly to rotation about the C-N bond along with some lengthening of this bond and increased pyramidal distortion at nitrogen as compared with that in the ground state. The STO-3G estimates of the barrier height (34-39 kJ mol-1) are in very poor agreement with experimental values (70-90 kJ mol-1), but 4- 31G energy evaluations for the STO-3G-optimized structures give much better estimates (62-80 kJ mol-1). Contrary to a previous report, use of the 4-31G extended basis set for geometry optimization suggests that only the lower-energy member (NH2 cis to CO) of the above pair is a true transition state for internal motion of formamide; its energy relative to that of the 4-31G-optimized ground state (planar) is 83.5 kJ mol-1, very close to the midpoint of the experimental range. The transition state appears to lie in a region of the 4-31G energy surface that is relatively flat with respect to pyramidal distortion at nitrogen; constraining the amino group to planarity raises the calculated energy by only 6.5kJmol-1.

scholarly journals Theoretical Study for Potential Energy Curves, Dissociation Energy and Molecular Properties for (LiH, H2, HF) Molecules

2015 ◽  
Vol 59 ◽  
pp. 137-146
Author(s):  
Adil Nameh Ayaash
Keyword(s):  
Binding Energy ◽  
Potential Energy ◽  
Electronic Properties ◽  
Ground State ◽  
Theoretical Study ◽  
Potential Energy Curves ◽  
Spectroscopic Constants ◽  
Electron Affinities ◽  
Dissociation Energies ◽  
Gaussian Program

A theoretical study has been carried out of calculating dissociation energies and potential energy curves (Deng-Fan potential and Varshni potential) and molecular parameters of of ground state of diatomic molecules (LiH, H2, HF). Dissociation energies and potential energy curves depended on spectroscopic constants (ωe, ωexe, re, α, μ, β ,) and our results has been compared with experimental results. Molecular and electronic properties as εHOMO, εLUMO, ionization potentials (IP), electron affinities (EA) and binding energy was performed by using B3P86/6-311++g** method and Gaussian program 03, the results is well in a agreement with that of other researchers.

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