Context_1 : A van der Waals molecule is a weakly bound complex of atoms or molecules held together by intermolecular attractions such as van der Waals forces or by hydrogen bonds. The name originated in the beginning of the 1970s when stable molecular clusters were regularly observed in molecular beam microwave spectroscopy. Context_2 : Johannes Diderik van der Waals (] ; 23 November 1837 – 8 March 1923) was a Dutch theoretical physicist and thermodynamicist famous for his work on an equation of state for gases and liquids. Context_3 : In condensed matter physics and physical chemistry, the Lifshitz theory of Van der Waals forces, sometimes called the macroscopic theory of Van der Waals forces, is a method proposed by Evgeny Mikhailovich Lifshitz in 1954 for treating Van der Waals forces between bodies which does not assume pairwise additivity of the individual intermolecular forces; that is to say, the theory takes into account the influence of neighboring molecules on the interaction between every pair of molecules located in the two bodies, rather than treating each pair independently. Context_4 : In chemistry, van der Waals strain is strain resulting from van der Waals repulsion when two substituents in a molecule approach each other with a distance less than the sum of their van der Waals radii. Van der Waals strain is also called van der Waals repulsion and is related to steric hindrance. One of the most common forms of this strain is eclipsing hydrogen, in Alkanes. Context_5 : The van der Waals surface of a molecule is an abstract representation or model of that molecule, illustrating where, in very rough terms, a surface might reside for the molecule based on the hard cutoffs of van der Waals radii for individual atoms, and it represents a surface through which the molecule might be conceived as interacting with other molecules. Also referred to as a "van der Waals envelope," the van der Waals surface is named for Johannes Diderik van der Waals, a Dutch theoretical physicist and thermodynamicist who developed theory to provide a liquid-gas equation of state that accounted for the non-zero volume of atoms and molecules, and on their exhibiting an attractive force when they interacted (theoretical constructions that also bear his name). van der Waals surfaces are therefore a tool used in the abstract representations of molecules, whether accessed, as they were originally, via hand calculation, or via physical wood/plastic models, or now digitally, via computational chemistry software. Practically speaking, CPK models, developed by and named for Robert Corey, Linus Pauling, and Walter Koltun, were the first widely used physical molecular models based on van der Waals radii, and allowed broad pedagogical and research use of a model showing the van der Waals surfaces of molecules. Context_6 : A molecular solid is a solid consisting of discrete molecules. The cohesive forces that bind the molecules together are van der Waals forces, dipole-dipole interactions, quadrupole interactions, π-π interactions, hydrogen bonding, halogen bonding, London dispersion forces, and in some molecular solids, coulombic interactions. Van der Waals, dipole interactions, quadrupole interactions, π-π interactions, hydrogen bonding, and halogen bonding (2-127 kJ mol) are typically much weaker than the forces holding together other solids: metallic (metallic bonding, 400-500 kJ mol), ionic (Coulomb’s forces, 700-900 kJ mol), and network solids (covalent bonds, 150-900 kJ mol). Intermolecular interactions, typically do not involve delocalized electrons, unlike metallic and certain covalent bonds. Exceptions are charge-transfer complexes such as the tetrathiofulvane-tetracyanoquinodimethane (TTF-TCNQ), a radical ion salt. These differences in the strength of force (i.e. covalent vs. van der Waals) and electronic characteristics (i.e. delocalized electrons) from other types of solids give rise to the unique mechanical, electronic, and thermal properties of molecular solids. Context_7 : Helium is the most unreactive element, so it was commonly believed that helium compounds do not exist at all. Helium's first ionization energy of 24.57 eV is the highest of any element. Helium has a complete shell of electrons, and in this form the atom does not readily accept any extra electrons or join with anything to make covalent compounds. The electron affinity is 0.080 eV, which is very close to zero. The helium atom is small with the radius of the outer electron shell at 0.29 Å. The atom is very hard with a Pearson's hardness of 12.3 eV. It has the lowest polarizability of any kind of atom. However very weak van der Waals forces exist between helium and other atoms. This force may exceed repulsive forces. So at extremely low temperatures helium may form van der Waals molecules. Also its atomic number is 2 and atomic mass is 4 Context_8 : In physical chemistry, the van der Waals forces, named after Dutch scientist Johannes Diderik van der Waals, are distance-dependent interactions between atoms or molecules. Unlike ionic or covalent bonds, these attractions are not a result of any chemical electronic bond, and they are comparatively weak and more susceptible to being perturbed. Van der Waals forces quickly vanish at longer distances between interacting molecules. Context_9 : London dispersion forces (LDF, also known as dispersion forces, London forces, instantaneous dipole–induced dipole forces, or loosely van der Waals forces) are a type of force acting between atoms and molecules. They are part of the van der Waals forces. The LDF is named after the German-American physicist Fritz London. Context_10 : Synthetic setae emulate the setae found on the toes of a gecko and scientific research in this area is driven towards the development of dry adhesives. Geckos have no difficulty mastering vertical walls and are apparently capable of adhering themselves to just about any surface. The 5-toed feet of a gecko are covered with elastic hairs called setae and the end of these hairs are split into nanoscale structures called spatulae (because of their resemblance to actual spatulas). The sheer abundance and proximity to the surface of these spatulae make it sufficient for van der Waals forces alone to provide the required adhesive strength. Following the discovery of the gecko’s adhesion mechanism in 2002, which is based on van der Waals forces, biomimetic adhesives have become the topic of a major research effort. These developments are poised to yield families of novel adhesive materials with superior properties which are likely to find uses in industries ranging from defense and nanotechnology to healthcare and sport. fact_1 : In physical chemistry, the van der Waals forces, named after Dutch scientist Johannes Diderik van der Waals, are distance-dependent interactions between atoms or molecules. fact_2 : Johannes Diderik van der Waals (] ; 23 November 1837 – 8 March 1923) was a Dutch theoretical physicist and thermodynamicist famous for his work on an equation of state for gases and liquids. Question: In what year was the physicist after whom the van der Waals forces were named born?
Output: 1837