摘要:

The use of intermolecular perturbation theory to rationalise intermolecular forces and to provide a framework for concepts of intermolecular interactions has been routine for many years. It has long been assumed, however, that the route to accurate calculations of intermolecular potentials lies throughabinitiosupermolecule calculations, and it is only in relatively recent times that this view has been challenged. It is now clear that accurate intermolecular potentials can be constructed for regions where the molecules do not overlap by assembling the components described by long‐range intermolecular perturbation theory−the electrostatic, induction and dispersion terms−though perturbation theory itself does not necessarily provide the best way to calculate them. At short range, the repulsion must be added, and the long‐range terms modified to account for the effects of overlap. Here too, perturbation theory provides a useful route to accurate numbers. At present, the resulting potentials are usually too elaborate for use in simulations on large molecules. However an understanding of accurate potentials is the prerequisite to the construction of simpler models that make large calculations feasible without sacrificing accuracy unnecessarily.

ISSN:0094-243X    

DOI:10.1063/1.41356

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

In this paper we describe a recently proposed formalism for computing quantum response properties with quantum Monte Carlo (QMC) techniques. It is explained how this general formalism may be used to compute dynamic multipole polarizabilities as well as perturbational components of intermolecular interaction energies. Illustrative calculations for the dynamic dipole polarizability of the helium atom and for the perturbational components of the interaction energy of He2are presented. The practical limitations of this new scheme are discussed.

ISSN:0094-243X    

DOI:10.1063/1.41339

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Theab‐initioMolecular Dynamics method, due to Car and Parrinello, is described and its potential for application to biological problems assessed. The application of the method to dynamical problems in which chemical bonds are broken and formed is illustrated and attention focussed on the modifications to the original method which are required to obtain the correct dissociation limits and to achieve adiabatic dynamics.

ISSN:0094-243X    

DOI:10.1063/1.41316

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Recent progress in the use of continuum electrostatics to treat solute‐solvent interactions will be discussed. The new developments are in the spirit of traditional dielectric models in that the solute is treated explicitly while the solvent is treated as a dielectric continuum. Numerical methods now make it possible to describe the solute in atomic detail and consequently to calculate solvation energies as well as charge‐charge interactions. Electronic polarizability can also be incorporated into the treatment. Our approach to the hydrophobic effect considers it as a form of macroscopic surface tension. It is demonstrated that the standard method of extracting solvation free energies from solubility data, which relies on measuring concentrations in mole fractions, is based on an incorrect approximation. A theory which accounts for volume differences between solute and solvent leads to solvation free energies of hydrocarbons which, when analyzed in terms of surface area, yield a microscopic surface tension of about 47 cal/mole/A˚2. Much of the remaining discrepancy with the macroscopic value of 72 cal/mole/A˚2can be accounted for with a simple geometric model which treats local curvature. The availability of macroscopic treatments of both electrostatic and hydrophobic free energies opens up the possibility obtaining total free energies for a large number of solvent dependent phenomena at nominal computational expense.

ISSN:0094-243X    

DOI:10.1063/1.41357

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We have looked for trends in Computational Chemistry from few electron systems to C60and water as solute and solvent. We concluded that it is necessary to find new techniques and to connect available methods among themselves, since the growth in computer speed, even if impressive, will not be sufficient.

ISSN:0094-243X    

DOI:10.1063/1.41358

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The conformational energy surface of a polypeptide or protein has many local minima, and conventional energy minimization procedures reach only a local minimum (near the starting point of the optimization algorithm) instead of the global minimum (the multiple‐minima problem). Several procedures have been developed to surmount this problem, the most promising of which are: (a) build up procedure, (b) optimization of electrostatics, (c) Monte Carlo‐plus‐energy minimization, (d) electrostatically‐driven Monte Carlo, (e) inclusion of distance restraints, (f) adaptive importance‐sampling Monte Carlo, (g) relaxation of dimensionality, (h) pattern‐recognition, and (i) diffusion equation method. These procedures have been applied to a variety of polypeptide structural problems, and the results of such computations are presented. These include the computation of the structures of open‐chain and cyclic peptides, fibrous proteins and globular proteins. Present efforts are being devoted to scaling up these procedures from small polypeptides to proteins, to try to compute the three‐dimensional structure of a protein from its amino sequence.

ISSN:0094-243X    

DOI:10.1063/1.41359

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.41341

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.41342

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.41343

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.41344

出版商:AIP    

年代:1991

数据来源: AIP