Laws of classical physics

Molecular mechanics simulations use the laws of classical physics to predict the structures and properties of molecules. Molecular mechanics methods are available in many computer programs, including MM3, HyperChem, Quanta, Sybyl, and Alchemy. There are many different molecular mechanics methods. Each one is characterized by its particular/orce eW. A force field has these components ... 

According to modern science, all various kinds of matter consist essentially of a few types of elementary particles combined together in different ways. Since these particles do not obey the laws of classical physics but the laws of modern wave mechanics, the problem of the constitution of matter is a quantum-mechanical many-particle problem of a much higher degree of complexity than even the famous classical three-body problem. 

In the early development of the atomic model scientists initially thought that, they could define the sub-atomic particles by the laws of classical physics—that is, they were tiny bits of matter. However, they later discovered that this particle view of the atom could not explain many of the observations that scientists were making. About this time, a model (the quantum mechanical model) that attributed the properties of both matter and waves to particles began to gain favor. This model described the behavior of electrons in terms of waves (electromagnetic radiation). 

At the tip s closest approach to the surface, electrons may flow from the instrument to the surface, or vice versa. According to the laws of classical physics, this flow of electrons is not possible because of the repulsion of like charges (in electron clouds) on the two materials. The laws of quantum mechanics, however, do allow some... 

In investigating the highly different phenomena in nature, scientists have always tried to find some fundamental principles that can explain the variety from a basic unity. Today they have shown not only that all the various kinds of matter are built up from a rather limited number of atoms but also that these atoms are composed of a few basic elements or building blocks. It seems possible to understand the innermost structure of matter and its behavior in terms of a few elementary particles electrons, protons, neutrons, photons, etc., and their interactions. Since these particles obey not the laws of classical physics but the rules of modem quantum theory of wave mechanics established in 1925, there has developed a new field of quantum science which deals with the explanation of nature on this basis. 

If a metal particle, independent of the element, is reduced in one, two, or in all three dimensions to such an extent that the mobility of the electrons is decisively restricted, one speaks of size quantization because the electrons no longer follow the laws of classical physics based on the statistics of an inflnite assembly of atoms in three dimensions, but rather obey quantum mechanical mles as they are used to describe atoms or molecules. Figure 1 illustrates the formal transition from 3D to a OD state, represented by a so-called quantum dot with three-dimensional quantum confinement. ... 

Detailed discussion of quantum mechanics (149) is clearly beyond the scope of this review, and its applications to molecular mechanics and modeling will be briefly summarized. Molecular mechanics is based on the laws of classical physics and deals with electronic interactions by highly simplified approximations such as Coulomb s law. All forces operating in intermolecular interactions are essentially electronic in nature. Any effort to quantitate those forces requires detailed information... 

In addition to the fact that the electrons fly on circular paths, Bohr also postulated that only certain orbits are permitted. Transitions between these orbits occurred immediately or spontaneously without the possibility to take any intermediate positions. It is impossible to understand these postulates with the laws of classical physics. Only quantum mechanics could explain the second Bohr postulation. 

Thomson had speculated as to the arrangement of the electrons, but his theory gave way to that of Rutherford who in 1911 proposed an atom in which most of the mass was concentrated in the nucleus and the electrons moved at varying speeds in circular or elliptical orbits, centred on the" nucleus. Soon this theory met with the criticism that on the laws of classical physics the electron, being a charged particle, would gradually fall into the nucleus as it revolved. 

If we examine the heat capacities of polyatomic gases. Table 4.3, we find two points of disagreement between the data and the equipartition law prediction. The observed heat capacities (1) are always substantially lower than the predicted values, and (2) depend noticeably on temperature. The equipartition principle is a law of classical physics, and these discrepancies were one of the first indications that classical mechanics was not... 

At the size scale that we live in — the big stuff that we see in everyday life (the macro world) — there s a set of physics laws that we use to help us understand the processes around us. These are called the laws of classical physics, that allow us to understand tides, the effect of gravity, and lots more. You can test these theories in your backyard, if you want to. 

Molecular mechanics and MD simulations use the law of classical physics to predict the structure and properties of molecule. These calculations perform computations based on the interactions among the nuclei and do not explicitly treat the electrons in a molecular system. This approximation makes them quite inexpensive and allows its use for very large system containing thousands of electrons. However the limitations associated with these methods are, they achieve good results for a limited class of molecules. Due to the negligence of electrons, these methods cannot treat chemical problems where electronic effects predominate [Young, 2001 Ramachandran et al., 2008 Foresman, 2004]. 

What was true for Nagaoka s Saturnian atom was also true, theoretically, for the atom Rutherford had found by experiment. It the atom operated by the mechanical laws of classical physics, the Newtonian laws that govern relationships within planetary systems, then Rutherford s model should not work. But his was not a merely theoretical construct. It was the result of real physical experiment. And work it clearly did. It was as stable as the ages and it bounced back alpha particles like cannon shells. 

Experience has shown that a quantitative description of the properties of atomic systems is not possible on the basis of the laws of classical physics. Quantum physics represents an attempt at a generalisation of these laws in the sense that a certain constant, Planck s constant, has a finite value A== 6 55.10 erg sec in contrast to classical physics, corresponding to the limit A=0, just as relativistic physics is a generalisation of non-relativistic physics, the latter arising from the former by passing from a finite value of the velocity of light c to an infinite value. Quantum physics in its present form appears adequate for dealing with all questions in which the internal constitution of the electron and the atomic nuclei as well as the theory of relativity need not be taken into ac-... 

Laws of classical physics can be used to derive an equation which describes the intensity of blackbody radiation as a function of frequency for a flxed temperature -the result is known as the Rayleigh-Jeans law. Although the Rayleigh-Jeans law agrees with experimental data for low frequencies (long wavelengths), it diverges... 

It might seem that the Schrodinger equation is unfounded. As a matter of fact, it cannot be derived either from laws of classic physic or from any known dependences. However, the equation is substantiated by correctly predicting of a number of natural phenomena. 

The motion of objects in the everyday world can be well described by the laws of classical physics—a description of the physical world that began with the development of the laws of motion by Isaac Newton. These laws were enormously successful as a unifying principle in physics until the end of the nineteenth century. 

At the end of the nineteenth century, scientists began to realize that the laws of classical physics were incompatible with a number of new experiments that probed the nature of atoms and molecules and their interaction with light. Through the work of a number of scientists over the first three decades of the twentieth century, a new theory—quantum mechanics—was developed that was able to explain the behavior of objects on the atomic and molecular scale. 

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