# Ry/Fragment 045 01

## < Ry

31.371Seiten in
diesem Wiki

### Wikia ist eine gebührenfreie Seite, die sich durch Werbung finanziert. Benutzer, die Adblocker einsetzen, haben eine modifizierte Ansicht der Seite. Wikia ist nicht verfügbar, wenn du weitere Modifikationen in dem Adblocker-Programm gemacht hast. Wenn du sie entfernst, dann wird die Seite ohne Probleme geladen.

 Typus KomplettPlagiat Bearbeiter Klgn Gesichtet
Untersuchte Arbeit:
Seite: 45, Zeilen: 1 ff. (entire page)
Quelle: Accelrys Inc. - Forcefield-Based Simulations 1998
Seite(n): 41, 42, Zeilen: 41:16ff; 42:1ff
where and are adjustable parameters that should depend on just the period, and neff is the effective number of (valence) electrons. Further assuming that α is proportional to R3 and that another equivalent expression to that in Equation (2.10) is:

$B_i \sim \varepsilon R^6$ (2.12)

where ε is a well depth, the following forms are deduced for the rules for van der Waals parameters:

$R_i=\frac{a}{(\mathit{IP})^{1/3}}+ \frac{b.n_{\mathit{eff}}^{1/3}}{(\mathit{IP})^{1/3}} \quad \textrm{and } \qquad \varepsilon_i=c(\mathit{IP})$ (2.13)

The van der Waals parameters are affected by the charge of the atom.

In ESFF we found it sufficient to modify the ionization potential (IP) of metal atoms according to their formal charge and hardness:

$\mathit{IP} = (\mathit{IP})_0 + q\eta _i$ (2.14)

and for nonmetals to account for the partial charges when calculating the effective number of electrons.

ESFF atom types are determined by hybridization, formal charge, and symmetry rules. In addition, the rules may involve bond order, ring size, and whether bonds are endo or exo to rings. For metal ligands the cis-trans and axial-equatorial positionings are also considered. The additions of these latter types affect only certain parameters (for example, bond order influences only bond parameters) and thus are not as powerful as complete atom types. In one sense they provide a further refinement of typing beyond atom types.

The ESFF has been parameterized to handle all elements in the periodic table up to radon. It is recommended for organometallic systems and other systems for which other [force fields do not have parameters.]

[page 41]

where a´ and b´ are adjustable parameters that should depend on just the period, and neff is the effective number of (valence) electrons. Further assuming that α is proportional to R3 and that another equivalent expression to that in Eq. 14 is:

$B_i \sim \varepsilon R^6$ Eq. 16

where ε is a well depth, the following forms are deduced for the rules for van der Waals parameters:

$R_i=\frac{a}{(\mathit{IP})^{1/3}}+ \frac{b \cdot n_{\mathrm{eff}}^{1/3}}{(\mathit{IP})^{1/3}} \quad \textrm{and } \qquad \varepsilon_i=c(\mathit{IP})$ Eq. 17

The van der Waals parameters are affected by the charge of the atom.

In ESFF we found it sufficient to modify the ionization potential (IP) of metal atoms according to their formal charge and hardness:

$\mathit{IP} = (\mathit{IP})_0 + q\eta _i$ Eq. 18

[page 42]

and for nonmetals to account for the partial charges when calculating the effective number of electrons.

ESFF atom types (Table 32) are determined by hybridization, formal charge, and symmetry rules (Atom-typing rules in ESFF). In addition, the rules may involve bond order, ring size, and whether bonds are endo or exo to rings. For metal ligands the cis–trans and axial–equatorial positionings are also considered. The addition of these latter types affects only certain parameters (for example, bond order influences only bond parameters) and thus are not as powerful as complete atom types. In one sense they provide a further refinement of typing beyond atom types.

The ESFF forcefield has been parameterized to handle all elements in the periodic table up to radon. It is recommended for organometallic systems and other systems for which other forcefields do not have parameters.

 Anmerkungen The source is not given. Even the first person plural "we" is copied. Sichter (Klgn), WiseWoman