Category: Solid Solutions

The theoretical basis and approach to developing the solutions of various types of computational problems is briefly described in this section. This discussion is not meant to be exhaustive or comprehensive, but rather introductory, in nature. Several alternative techniques are available for solving the various types of problems; the following discussion is in most cases…

This page provides a limited web-based version of the Monte Carlo simulation in case you are not able to run it in IGOR Pro. There are a limited number of choices of interaction parameter, temperature and composition. Video clips generated by running the simulation in IGOR Pro show the progression from an initially disordered state…

Computer modelling is a useful tool in representing and predicting atomic processes. A simulation has been created using IGOR Pro, a powerful graphing, data analysis, and programming tool for scientists and engineers produced by WaveMetrics. IGOR Pro is available for both Windows and Macintosh and a demo version can be downloaded from the WaveMetrics website. If…

The precipitation of a solid phase from a liquid matrix is governed by a balance between the thermodynamic driving force and the energy penalty for creating new solid-liquid surface interfaces. This determines the size and shape of the precipitates. The precipitation of a solid phase from a solid parent phase is very similar. There are…

A mixture of equal quantities of cyclohexane and aniline contained in a sealed vial is heated to approximately 35 ºC (i.e. just above the critical temperature), using a water bath (or water from a hot tap). The mixture is allowed to cool, and a laser is pointed at the vial so that it shines onto…

The transition from a single phase to two phases (and vice-versa) can be easily demonstrated using a mixture of two suitable liquids. A mixture of cyclohexane and aniline can exist as two separate phases or as a single phase, depending on the temperature. The thermodynamic transition between these two states can be understood by considering…

A binary solid solution can show a phase diagram as follows: The solidus and liquidus separate the single phase regions. This is similar to the Cu-Ni phase diagram. If the system demonstrates exsolution, then there will be a region in the solid state where two solid phases form from the solid solution. This is common and…

The free energy of mixing is defined as: ΔGmix = ΔHmix – TΔSmix The variation in free energy as a function of composition and temperature can be considered for three different situations: an ideal solution, a non-ideal solution with a positive enthalpy of mixing, and a non-ideal solution with a negative enthalpy of mixing. 1. Ideal solid solution, ΔHmix = 0…

Entropy The entropy of the two endmembers, A and B, of a solid solution are SA and SB, and are mainly vibrational in origin (i.e. related to the structural disorder caused by thermal vibrations of the atoms at finite temperature). The entropy of the solid solution will always be greater than the entropy of the mechanical mixture. The…

Olivine is a name for a series of minerals with the formula M2SiO4, where M is most commonly Fe or Mg. Fayalite (Fe2SiO4) and forsterite (Mg2SiO4) form a substitutional solid solution where the iron and magnesium atoms can be substituted for each other without significantly changing the crystal structure. As mentioned previously, there is a size mismatch of only about 7%…