Polarization Gaussian p Functions for the Beryllium Atom: Ab initio Calculations on BeH2 and BeH+

1975 ◽  
Vol 53 (22) ◽  
pp. 2512-2516 ◽  
Author(s):  
P. G. Mezey ◽  
I. G. Csizmadia ◽  
O. P. Strausz
Keyword(s):  
Excited State ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Ground State ◽  
Optimization Procedure ◽  
Energy Functional ◽  
Basis Set ◽  
Negative Ion ◽  
Gaussian Basis Set ◽  
Orbital Exponents

A set of Gaussian p orbital exponents was obtained by optimizing a (9s5p) Gaussian basis set for an excited state of the beryllium atom and the ground state of the beryllium negative ion. In the optimization procedure the method of conjugate gradients was applied for the energy functional. The optimum (9s5p) basis set was tested on the BeH2 and BeH+ structures.

Ammonia oxide. I. Geometry and stability

1976 ◽  
Vol 29 (2) ◽  
pp. 231 ◽  
Author(s):  
BT Hart
Keyword(s):  
Excited State ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Bond Length ◽  
Ground State ◽  
Tautomeric Form ◽  
Potential Curve ◽  
Repulsive Potential ◽  
Means Of Production

Ab initio calculations, utilizing Gaussian lobe functions, are reported for the molecule ammonia oxide, NH3O. Results indicate that ammonia oxide has a bound ground state, an abnormally long NO bond length (169 pm) and is 125.9 kJ mol-1 less stable than the tautomeric form hydroxylamine, NH2OH. Possible means of production of the molecule are discussed. The 3E excited state of ammonia oxide was found to have a repulsive potential curve. Possible reasons for this instability are advanced.

Optimum Gaussian basis set for the Bromine atom. Ab initio calculations on the HBr molecule

1975 ◽  
Vol 40 (1) ◽  
pp. 75-80 ◽  
Author(s):  
Paul G. Mezey ◽  
Min H. Lien ◽  
Keith Yates ◽  
Imre G. Csizmadia
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Bromine Atom ◽  
Basis Set ◽  
Gaussian Basis Set

Ab initio electronic structure and direct dynamics simulations of CH3OCl

2009 ◽  
Vol 87 (7) ◽  
pp. 1022-1029
Author(s):  
Stephanie Y. Y. Wong ◽  
Pierre-Nicholas Roy ◽  
Alex Brown
Keyword(s):  
Electronic Structure ◽  
Excited State ◽  
Ab Initio ◽  
Ground State ◽  
Basis Set ◽  
Ab Initio Molecular Dynamics ◽  
Basis Sets ◽  
Excitation Energies ◽  
Direct Dynamics ◽  
Ab Initio Electronic Structure

The ground (X1A′) and two lowest lying excited singlet states (11A″ and 21A′) of methyl hypochlorite have been examined using ab initio electronic structure techniques to validate computationally efficient methods, upon which direct dynamics can be based, versus high-level ones, for which direct dynamics would be intractable. Ground-state equilibrium geometries and vibrational frequencies determined using density functional theory (DFT) with the 6-31G(d) basis set are tested against coupled-cluster theory (CCSD(T)) results from the literature. Vertical excitation energies and transition dipole moments calculated at the complete active space self-consistent field CASSCF/6-31+G(d) level of theory are benchmarked against multireference configuration interaction (MRCI) results with the aug-cc-pVXZ (X = D, T, Q) family of basis sets. The excited-state gradients that will govern the classical dynamics are compared for CASSCF/6-31+G(d) versus MRCI/aug-cc-pVXZ (X = D, T). To carry out the ab initio molecular dynamics (AIMD), existing electronic structure codes have been interfaced with the molecular modelling toolkit (MMTK), an open-source program library for molecular simulation applications. We use two examples to demonstrate the use of direct dynamics in MMTK: a canonical ground-state trajectory to sample positions and momenta, and an excited-state microcanonical trajectory based on CASSCF. The work presented here forms the basis for future study of the photodissociation of CH3OCl. As well, the implementation of AIMD within MMTK provides a useful tool for examining a variety of other research problems.

The negative ion BN−and its role in determining the ground state of BN via photodetachment. An MRDCI ab initio study

1993 ◽  
Vol 71 (10) ◽  
pp. 1581-1594 ◽  
Author(s):  
Robert C. Mawhinney ◽  
Pablo J. Bruna ◽  
Friedrich Grein
Keyword(s):  
Excited States ◽  
Ground State ◽  
Experimental Studies ◽  
Electron Attachment ◽  
Radiative Properties ◽  
Basis Set ◽  
Negative Ion ◽  
Resonant States ◽  
Gaussian Basis Set ◽  
Ci Calculations

Extensive multireference CI calculations using a contracted 6s5p3d1f Gaussian basis set on the B and N atoms indicate that the X2∑+, A2Π, and B2∑+ states of BN− are bound with respect to the electron attachment BN + e−. The 14∑+, 14Δ, 14∑−, and 14Π states of BN− are resonant states, all autodetaching into neutral BN. The electron affinity X3Π → X2∑+ is predicted to be 2.84 eV (with a best estimate of 3.10 eV). Other features studied for BN− include the infrared spectrum of the X2∑+ ground state as well as the electronic radiative properties involving the excited states A2Π and B2∑+. The present study supports a X3Π ground state for BN, with a1∑+ lying about 0.03 eV higher. As an alternative to optical spectroscopy on BN, experimental studies of the photodetachment spectrum of BN− are proposed in order to find the ordering and energetic separation of the lowest 3Π and 1∑+ states of BN.

Vicinal proton—proton coupling constants. Basis set dependence in SCF ab initio calculations

1993 ◽  
Vol 206 (1-4) ◽  
pp. 253-259 ◽  
Author(s):  
Jesús San-Fabián ◽  
Joaquín Guilleme ◽  
Ernesto Díez ◽  
Paolo Lazzeretti ◽  
Massimo Malagoli ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Coupling Constants ◽  
Basis Set ◽  
Proton Proton ◽  
Proton Coupling ◽  
Vicinal Proton
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