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Models and Scales

It is very common in the scientific community to make a 1-1 relation between scales of the system or phenomena to be simulated and the models or methods used. This relation is in general not correct. A physics equation is not scale limited, Newton’s law for example is applicable to all scales. The Review of Materials Modelling (see RoMM) endorsed by the EMMC community clearly  classifies models according to the entity described by the physics and not according to the the size (length scale) of the application or system. See Table below.

So instead of speaking of “describing the material across multiple scales”, it is much clearer to say: “describing the material across multiple granularity levels, electronic, atomistic, mesoscopic or continuum” etc.

A material at nm scale can be modelled by four type of models.

Use the word “granularity level” for the four types of model e/a/m/c. Reserve the word “scale” for length scale or time scale and hence aspects of the application/user case.

Towards establishing a standard

This notion based on the granularity levels expressed by the model entities is very fundamental to the European Materials Modelling Ontology and has been endorsed by the community through a CEN/WS MODA – Materials modelling – terminology, classification and metadata. This document defines basic fundamental terms that should be used in any accurate description or reporting of materials modelling activities. In particular it defines clear guidelines for building the MODA and includes clear definition of the model entity and granularity.

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