Theoretical “positive” and “negative” forms of calcite, viewed through the morphological methods of Bravais-Friedel-Donnay-Harker and Hartman-Perdok.

Predicting the growth morphology of crystals, from the knowledge of their structure, can be done by applying: a) the Bravais-Friedel-Donnay-Harker (BFDH) rule stating that higher the spacing dhkl, higher the morphological importance (MI) of the {hkl} form b) the Hartman and Perdok (HP) rule grounded on the idea that higher the attachment energy value, higher the corresponding growth rate (Rhkl ) and, consequently, lower the morphological importance of the {hkl} form. According to the BFDH rule both ‘positive’ and ‘negative’ calcite forms must have the same morphological importance i. e. they appearance probability may be the same. However, their occurrence is very different and only the ’positive’ forms are commonly found both in nature laboratory. A PBC analysis is being performed in order to find the F-faces of the ‘negative’ forms and then its surface energy is calculate