Recent content by gadong

According to http://arxiv.org/abs/1308.1542, the u parameter represents the relative position of two hexagonal close-packed sublattices in the structure (for example, in a binary compound like ZnO).

Some time ago I grew a large copper sulphate crystal, which looks like a piece of blue-coloured glass, about 3-4 mm thick. You can easily see things through the crystal (i.e. light passes easily, although it is tinted blue). However, no light from a red laser pointer can get through. The beam of...

The energetics of physisorption (van der Waals interactions) differ from those of chemisorption. What kind of adsorption systems are you interested in?

In the Debye model, vibrations can have any wavelength that is consistent with the periodicity of the crystal. The smallest wavelength (highest frequency) corresponds to the interatomic spacing. The longest wavelength (lowest frequency) corresponds to the size of the crystal itself. The...

eightsquare, It is not correct to attribute repulsive interatomic forces to electronic effects. For example, the forces between two atoms are due to energy changes in the entire two-atom system. The dominant contribution is the repulsive interaction between the two nuclei. I will work through...

More usually one would say that (electromagnetic) energy comes in the form of particles (known as photons). Each photon carries a certain amount of energy. Once you see radiation as particle-like, much of the difficulty is removed as this quantization is the expected behaviour of sub-atomic...

1. The S-G experiment demonstrates the effects of the spin magnetic moment, but is silent about the spin angular momentum. The idea that spin is connected to angular momentum - not just magnetism - is suggested by the relativistic analogue of the Schroedinger equation (the Dirac equation)...

OK, thanks MG. I'll write a few more things to maybe clarify. In day to day life, the forces of contact become apparent when objects are compressed relative to their equilibrium separation, which represents a potential energy minimum. The closer they approach, the more the potential energy of...

I assume you are referring to the LJ 6-12 potential. The R^6 term is an attractive part that arises from dispersion forces. The calculation, showing that R^7 is a better approximation, is outlined in the textbook Molecular Quantum Mechanics by PW Atkins. The R^12 term is arbitrary. A...

The latter (hbar/2), assuming that Δx and Δp are interpreted as standard deviations from their respective means.

http://xdb.lbl.gov/Section1/Sec_1-5.html The above link gives the sub-shell photoionization cross-sections for 15 elements (a pdf version is found in here: xdb.lbl.gov/xdb.pdf‎, section 1.5).

Suppose the photon energy is less than required to ionize the K shell (the K shell binding energy) - then no K shell electrons will be ejected (but electrons may be ejected from other shells). As the photon energy passes above the K shell energy, there will be a sudden onset in emission from...

The wave function is a sine function that goes to zero at the boundaries of a region of length a. Therefore, there must be an integral (1, 2, 3...) number of half-wavelengths in a region a. That is, a = integer*wavelength/2, or wavelength = 2a/integer. For the ground state, the integer...

DFT works for the lowest states of a given symmetry, of which there might be several. The calculation of excited state properties (e.g. absorption spectra) can be carried out using time-dependent DFT. More information here: http://en.wikipedia.org/wiki/Time-dependent_density_functional_theory.

If you mean that the DF theory itself is an approximation - no, it's exact. Practical implementations are approximations, however.