According to the Hall–Petch relationship, the strength of the materials grows with a decrease in the grain size. If I wanna study the impact of grain size on the mechanical properties of rocks using molecular dynamics methods, how to characterise the grain size of materials (e.g., rocks) using molecular dynamics methods?
The first thing to consider is the general shapes of your 'grains', whether they are equiaxed or textured (e.g. ellipsoidal). If they are relatively equiaxed, then measuring the average diameter of the grains should be fine.
In MD you would perhaps find the maximum distance between two points belonging to the same grain. Another option is to measure the volume, assume a generally spherical shape and derive a radius from that.
Something to note about Hall-Petch and MD though: if the grains are small on the absolute scale (say, 10s of nm in diameter) you will in fact see a reverse Hall-Petch effect, where decreasing grain size decreases strength.
The first thing to consider is the general shapes of your 'grains', whether they are equiaxed or textured (e.g. ellipsoidal). If they are relatively equiaxed, then measuring the average diameter of the grains should be fine.
In MD you would perhaps find the maximum distance between two points belonging to the same grain. Another option is to measure the volume, assume a generally spherical shape and derive a radius from that.
Something to note about Hall-Petch and MD though: if the grains are small on the absolute scale (say, 10s of nm in diameter) you will in fact see a reverse Hall-Petch effect, where decreasing grain size decreases strength.
I highly recommend this book to read (https://www.amazon.com/Molecular-Modelling-Principles-Applications-2nd/dp/0582382106)
I'm sure most of your questions will be quite addressed, which are about molecular modeling approaches and also their differences.
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