Van der Waals (VDW) interactions are probably the most basic type of interaction imaginable Any two molecules experience Van der Waals interactions Even macroscopic surfaces experience VDW interactions, but more of this later The physical process that leads to Van der Waals interactions is clear, but it is difficult to
forces are known as van der Waals or dispersion forces[3] The signi?cance of the ubiquitous van der Waals attractive force on the strength and properties of the bonding between ?bres in a paper sheet is still relatively unknown The strength of the van der Waals interaction can be predicted if the system Hamaker constant (A) is known[4]
Figure 2 shows six of the con?gurations we considered in the calculations Noting that no covalent bonds are formed between PTCDA and the surface, the key components of the interaction are the ionic attraction between the terminating O atoms and K+ ions in the surface and the vdW attraction between the molecule and the surface In Figs 2 a
Lecture 15 The van der Waals Gas (Ch 5) The simplest model of a liquid-gas phase transition - the van der Waals model of “real” gases – grasps some essential features of this phase transformation (Note that there is no such transformation in the ideal gas model) This will be our attempt to take intermolecular interactions into account
walls of the substrate may become important, additional intermolecular forces such as van der Waalls forces may be signi cant and issues of wetting and non wetting then arise An important and major application area is in the coatings industries including the preparation of thin lms, printing, painting and adhesives Our main interest is in the
An interesting estimation for strength of van der Waals forces is the case of fly on the ceiling Fly with downcast head opposes the gravity with van der Waals adhesion For A HAM = 10 kBTroom, l = 10 nm (~ 70 interatomic distance), the forces are balanced if cubically approximated fly has volume 8 cm 3 (? ~ 1 kg/m 3) For
in which the nonadditivity of the van der Waals dispersion forces arises in a very transparent way ones can explain the attraction between molecules atoms in all cases, as for sume additive van der Waals forces that led to a consider-
about different types of van der Waals forces 5 1 1 Dispersion force of attraction between two temporary Fig hydrogen bonding is regarded as being limited
In matter in general, attraction is the norm Geckos adhere to surfaces by the van der Waals force Autumn Consider a slope of 10-5: 100 nm rise over 1 cm