Hydrogen bonding semiempirical methods

AMI Cambridge Structural Database Carbohydrate Force Fields Conformational Analysis 1 Conformational Analysis 2 Conformational Analysis 3 Continuum Solvation Crystal Structure Calculations 1 Crystal Structure Calculations 2 Cyclodextrins Force Fields MM3 Hydrogen Bonding 1 Hydrogen Bonding 2 Hydrogen Bonds Semiempirical Methods Hyperconjugation MNDO Natural Bond Orbital Methods PM3 Solvation Carbohydrates. 

Hydrogen Bonding 1 Hydrogen Bonds Semiempirical Methods Water Clusters. 

AMI Divide and Conquer for Semiempirical MO Methods Green s Function Ionization Potentials in Semiempirical MO Theory Hydrogen Bonds Semiempirical Methods Localized MO SCF Methods MNDO/d Parameterization of Semiempirical MO Methods PM3 Polymers Semiempirical Calculations Population Analyses for Semiempirical Methods Semiempirical Vibrational Frequencies (Including Scaling). 

Another, more semiempirical, method is to assume that the only effect of the catalyst is to change the binding to the surface entropy and solvation effects are taken to be the same as for the solvated spices. This assumes that the hydrogen bonds to, e.g., OH are the same as the hydrogen bonding to OH [Roques and Anderson, 2004]. We... 

However, another study concluded that the changes of the hydrogen-bond stability may be important in biological processes. For these, the influence of local electric fields created by Li+, Na+, and Mg2+ ions on the properties and reactivity of hydrogen bonds in HF and HC1 dimer has been carried out by means of ab initio self-consistent field (SCF) method [33]. A few years later, the effect of intensity and vector direction of the external electric field on activation barriers of unimole-cular reactions were studied using the semiempirical MINDO/3 method [34]. However, both semiempirical and ab initio calculations were performed to study the multiplicity change for carbene-like systems in external electric fields of different configurations (carbene and silylene) and the factor that determines the multiplicity and hence the reactivity of carbene-like structures is the nonuniformity of the field [35]. 

The AMI (8) approximation to molecular orbital theory has been used for these studies. This method overcomes the problems that previous semiempirical methods (notably, MNDO) (9) have in describing hydrogen-bonds. It has been used with success in several hydrogen-bonding studies. (10-12) Ab initio studies of H-bonding systems are very sensitive to basis set and correction for electron-... 

A key advantage of semiempirical methods is that they give heats of formation directly. Small cyclic hydrocarbons are typically computed to be too stable, and sterically crowded structures are predicted to be too unstable. This is because semiempirical methods do not describe weak interactions well, e.g. those arising from London dispersion forces thus, they would not be suitable to describe, for instance, molecular structures that rely heavily on hydrogen bonding interactions. 

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