Foundations of Chemistry最新文献

The arrangement of elements in a summary table was celebrated in 2019 on the occasion of the 150th anniversary of the publication of Mendeleev’s early Periodic Table. This review traces the subsequent developments that led to the formulation of Mendeleev’s later Periodic Table in 1872, highlighting the pivotal contribution of another key figure, Julius Lothar Meyer. Both chemists had attended the Karlsruhe Congress in September 1860, where Stanislao Cannizzaro presented his influential theory for determining atomic weights, an essential step toward systematic classification. Building on these foundations, Mendeleev and Meyer developed their respective approaches to organizing the Periodic Table, including the prediction of as-yet-undiscovered elements. A subtle yet important distinction emerges in their perspectives: while Meyer chose to reserve a restricted role for prediction, Mendeleev had the boldness to explicitly describe both the presumed chemical properties and the expected atomic weights of the missing elements, and even went so far as to assign them provisional names. Some of the missing elements (e.g., Ga, Sc, and Ge) were discovered soon after, whereas others, such as Tc (from the Greek technetos, meaning “artificial”) and At (from the Greek àstatos, meaning “unstable”), were produced artificially much later.

High-Performance Liquid Chromatography (HPLC) is widely used in the pharmaceutical and fine chemical industries to establish chemical substance identity. HPLC is an analytical chromatographic technique, i.e., it is used to establish chemical substance identity and purity. Preparative chromatography is used to isolate usable quantities of chemical substances. A sample which gives rise to a chromatographic peak under specified conditions can be said to possess the property of containing the particular chemical substance to which that peak can be assigned. The chemical substance could be said to be part of the analysed sample in the mereological sense. A concern is raised by the possibility noted by Harré and Llored with respect to mereology, that it may be fallacious to infer that the substantive products of an analytical procedure are parts of the substance on which the procedure was performed. Instances arising from preparative chromatography show that that possibility exists, however, the value of analytical chromatography to chemical practice is that the chemical substances which are separated are considered as having being part of the sample analysed. Spatial and temporal aspects of chromatographic assignment of chemical substance properties are considered. A chromatographic peak could also be regarded as an ‘affordance’, i.e., arising from the interaction of the apparatus and the world. Consideration of chromatography in mereological terms is also discussed with relation to issues such as parthood, remainder and relation to concepts of purity, and the applicability of the concepts of fusion and disjointness.

A recent paper in this journal has argued strongly in favour of the view that going beyond the Born-Oppenheimer approximation in quantum chemistry offers an explanation of chemical facts by quantum theory. In essence the claim amounts to believing that any molecule’s chemistry can be accounted for in terms of the discrete energy levels of the Coulomb Hamiltonian for the collection of electrons and nuclei specified by the molecular formula without reference to the traditional Born-Oppenheimer arguments. This is ‘The Isolated Molecule’ model since only the internal interactions of the electrons and nuclei are considered. The Comment suggests that such an approach is only suitable for atoms and diatomic molecules since there is no potential energy surface defined, and diagonalization of the Coulomb Hamiltonian, ({textsf{H}}), simply yields energy levels for the whole molecule. The associated eigenfunctions provide a basis for irreducible representations of the Galilean relativity group augmented by space-inversion and appropriate permutation groups (for identical particles). Some misquotations from the author’s work are corrected.

A scientific law generally models the behaviour associated with some physical phenomenon such that it can be described in terms of y = mx + c. The turn of the ninetieth century saw the introduction of the laws of chemical composition and Dalton’s postulates, but these ideas are very different and cannot be assessed using the techniques of continuous mathematics. In this paper we review Dalton’s postulates and the corresponding types of chemical reaction process in the light of cellular automata and Wolfram’s new kind of science (NKS). We find that the bond forming, bond breaking and substitution (STAD) mechanistic steps that occur during chemical reactions have a broad correspondence with the rules of cellular automata, a concept of discrete mathematics. Wolfram identified that cellular automata have four general classes of behaviour, likewise, we propose that chemical reaction processes can be grouped into four corresponding rather general classes.

The article sets out to clarify a number of confusions that exist in connection with the Born–Oppenheimer approximation (BOA) (Born-Oppenheimer, 1927). It is generally claimed that chemistry cannot be reduced to quantum mechanics because of the nature of this commonly used approximation in quantum chemistry, that is popularly believed to require a ‘clamping’ of the nuclei. It is also claimed that the notion of molecular structure, which is so central to chemistry, cannot be recovered from the quantum mechanical description of molecules and that it must be imposed by hand through the BOA. Such an alleged failure of reduction is then taken to open the door to concepts such as emergence and downward causation. Another mistaken view is that chemists have no choice but to use the BOA whereas there is an entire sub-discipline which involves non-Born Oppenheimer calculations, and which regularly and successfully calculates many chemical and biochemical properties of molecules. Yet another misconception, according to the present author, is the view that the application of the BOA represents a violation of the Heisenberg Uncertainty Principle. Many of the claims made in the philosophy of chemistry community are based on the highly technical papers of authors such as Sutcliffe and Wooley, many of which date from about 50 years ago. While these authors remained skeptical of the possibility of recovering molecular structure from quantum mechanics, others maintained that it would eventually possible to do so. Significant progress has now been made in this direction. For example, whereas it is claimed that the full, or Coulombic Hamiltonian, for a molecule precludes the existence of molecular dipoles, some recent calculations have succeeded in obtaining the exact value of dipole moment of the LiH molecule. Even more significantly, a group in Norway has now succeeded in recovering the structure of the D₃⁺ molecule in a completely ab initio manner without applying the BOA, but through the use of a Monte Carlo approach.

It is generally accepted that the exact solution to the Schrödinger equation cannot be expressed as a single determinant of orbitals. This assertion is the result of the traditional approach taken to solve the N-electron problem in 3N dimensions, namely, integration over coordinates. Integration over coordinates averages the various interactions leading to approximations to the exact solution; this loss of local information is sought to be recovered through multi-determinant formalisms. We introduce the local Schrödinger equation (in ({mathbb{R}}^{6})) from the energy density representation of the Schrödinger equation (in ({mathbb{R}}^{3N})). A proof is presented that shows that there exists a single determinant representation (of one-electron orbitals) for the exact wavefunction that satisfies the Schrödinger equation. We also show that the exact orbitals that describe the system have the same orbital energy, thereby equalising the chemical potential within the system.