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Fragmentation fuzzy electron density

Transferability, adjustability, and additivity of fuzzy electron density fragments... [Pg.56]

If the electron density partitioning results in subsystems without boundaries and with convergence properties which closely resemble the convergence properties of the complete system, then it is possible to avoid one of the conditions of the Holographic Electron Density Fragment Theorem , by generating fuzzy electron density fragments which do not have boundaries themselves, but then the actual subsystems considered cannot be confined to any finite domain D of the ordinary three-dimensional space E3. [Pg.68]

The fundamental tool for the generation of an approximately transferable fuzzy electron density fragment is the additive fragment density matrix, denoted by Pf for an AFDF of serial index k. Within the framework of the usual SCF LCAO ab initio Hartree-Fock-Roothaan-Hall approach, this matrix P can be derived from a complete molecular density matrix P as follows. [Pg.68]

This, in turn, implies the exact additivity of the fuzzy electron density fragments p1 (r) as given by Equation (39). [Pg.70]

In structure determination from X-ray diffraction data, it sometimes happens that, on the Fourier maps, parts of the coming out structure are unclear. Fuzzy electron density maps may present problems in determining even the approximate positions of the respective fragments of the structure being analyzed. For example, the layered structure of the inclusion (intercalation) compound formed by Ni(NCS)2 (4-methylpyridine)4 (host) and methylcellosolve (guest) [1], The guest molecules are (Fig. 11.1) located on twofold crystal axes of unit cell symmetry and are orientationally disordered as shown in the picture. [Pg.242]

The Mulliken-Mezey Additive Fuzzy Electron Density Fragmentation Method... [Pg.164]

Linear Homotopies of Fuzzy Electron Density Fragments... [Pg.164]

In the following two sections two approaches will be discussed where molecular fragments are represented by fuzzy electron density models. [Pg.173]

Based on the fragment density matrix Pk for the k-th fragment, the electron density of Mezey s fuzzy density fragment pk(r) is defined as... [Pg.175]

The fuzzy electron density fragment additivity rules (23) - (27) are exact at any given ab initio LCAO level, hence the reconstruction of the calculated electronic density p(r) of the given molecule from the corresponding fuzzy fragment electron densities pk(r) is also exact. [Pg.176]

The additive fuzzy electron density fragmentation scheme of Mezey is the basis of the Molecular Electron Density Lego Assembler (MEDLA) method [67,70-72], reviewed in section 4. of this report, where additional details and applications in local shape analysis are discussed. The MEDLA method was used for the generation of the first ab initio quality electron densities for macromolecules such as proteins [71,72] and other natural products such as taxol [66],... [Pg.178]

The exact additivity of the fragment density matrices Pk and the fuzzy fragment densities pk(r) defined according to Mezey s scheme (eqs. (23)-(27)) motivates the terminology additive, fuzzy electron density fragmentation method. The fuzzy electron density fragment additivity rule is exact at the given ab initio LCAO level. [Pg.192]

The linearity of density expressions (16) and (24) in the corresponding density matrices ensures exact additivity for the fuzzy electron density fragments, as described by eq. (27) ... [Pg.192]

The application of the additive fuzzy electron density fragments for the building of electron densities of large molecules is called the Molecular Electron Density Lego Assembler method, or MEDLA method [5,37,66,67,70-72],... [Pg.193]

Even if each of the fuzzy electron density fragments pk(r) originate from a different molecule, a good approximation to the total electron density p(r) of the target molecule can be obtained using eq. (27) ... [Pg.193]

Density functional theory provides the means for defining fragment energies, based on the following, simple principle the fuzzy electron density fragment of a functional group, together with the associated set of nuclei, is treated as a complete... [Pg.214]

Quantum chemical functional groups have been defined as fuzzy electron density fragments (AFDF fragments) associated with a family of nuclei fk,... [Pg.596]

The computation of fuzzy electron density fragments and the construction of ab initio quality macromolecular electron densities is a novel approach to the quantum-chemical study and detailed modeling of large molecules. The additive ffizzy density fragmentation (AFDF) scheme of Mezey, described in a general form elsewhere, -is employed in the molecular electron density lego assembler (MEDLA) technique of Walker... [Pg.200]


See other pages where Fragmentation fuzzy electron density is mentioned: [Pg.70]    [Pg.74]    [Pg.172]    [Pg.175]    [Pg.176]    [Pg.176]    [Pg.190]    [Pg.190]    [Pg.192]    [Pg.192]    [Pg.193]    [Pg.193]    [Pg.195]    [Pg.195]    [Pg.196]    [Pg.205]    [Pg.215]    [Pg.215]    [Pg.618]    [Pg.140]   


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