Ground State of

The ground-state electronic configuration of H2O, with eight valence electrons (two from the hydrogens. 2Alp or six from oxygen), is therefore 

We note that all the electrons must be paired, and H 0 is diamagnetic. There are four electrons in a orbitals, giving two tr bonds. 

The bond angle in HjS is 92 , much closer to the 90° expected for pure p bonding. In HtS, it is probable that there is strong 3 -1 bonding. This is consistent with the fact that the interelectronic repulsions in 3p orbitals on sulfur are known to be less than the interelectronic repulsions in Ip orbitals on oxygen. 

The electrons in 7 orbitals in HjO spend more time near the oxygen than near the hydrogens, owing to the larger electronegativity of 

The H2O molecule has a dipole moment of 1.844 D. The moment is due to the charge separation described above as well as to lone pairs, as shown in Fig. 7 8. Each H—O bond has a small bond dipole 

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It should be mentioned that the single-particle Flamiltonians in general have an infinite number of solutions, so that an uncountable number of wavefiinctions [/ can be generated from them. Very often, interest is focused on the ground state of many-particle systems. Within the independent-particle approximation, this state can be represented by simply assigning each particle to the lowest-lying energy level. If a calculation is... 

Kuhn B, Rizzo T R, Luckhaus D, Quack M and Suhm M A 1999 A new six-dimensional analytical potential up to chemically significant energies for the electronic ground state of hydrogen peroxide J. Chem. Phys. Ill 2565-87... 

Wlien considering the ground state of the Be atom, the following four antisyimnetrized spin-orbital products are found to have the largest amplitudes ... 

Boys S F 1950 Eleetronie wave funetions II. A ealeulation for the ground state of the beryllium atom Proc. R. See. A 201 125-37 Shavitt I 1977 The method of eonfiguration interaetion Modern Theoretical Chemistry vo 3, ed H F III Sehaefer (New York Plenum) pp 189-275... 

Eckstein FI, Schattke W, Reigrotzki M and Redmer R 1996 Variational quantum Monte Carlo ground state of GaAs Phys. Rev. B 54 5512-15... 

Ceperly D M and Alder B J 1980 Ground state of the electron gas by a stochastic method Phys. Rev. Lett. 45 566-9... 

Figure 2. Total differential cross-section versus laboratory scattering angle for vibrational ground state of hydrogen molecules in single collisioins with 30-eV protons.

To use direct dynamics for the study of non-adiabatic systems it is necessary to be able to efficiently and accurately calculate electronic wave functions for excited states. In recent years, density functional theory (DFT) has been gaining ground over traditional Hartree-Fock based SCF calculations for the treatment of the ground state of large molecules. Recent advances mean that so-called time-dependent DFT methods are now also being applied to excited states. Even so, at present, the best general methods for the treatment of the photochemistry of polyatomic organic molecules are MCSCF methods, of which the CASSCF method is particularly powerful. 

HOMO and LLMO, also known as Frontier orbitals, are important in in tcrprcLitig results of a calculation (see Frontier Molecular Orbitals on page 141). You can use these m olecular orbiLals to comptiLe the lowest excited electronic singlet state of molecules and the ground states of radicals. 

Bingiiam R C, M J S Dewar and D H Lo 1975a. Ground States of Molecules. XXV. MINDO/3. An improved Version of the MINDO Semi-empirical SCFMO Method. Journal of the American Chemical Society 97 1285-1293. 

Bingham R C, M J S Dewar and D H Lo 1975b. Ground States of Molecules. XXVI. MINDO/3. 

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