Pieter "Piet" Hartman (born 1929 – died 2021) was a Dutch crystallographer and mineralogist, widely recognized for his fundamental contributions to the understanding of crystal growth and morphology. He is best known as the co-developer, alongside W.G. Perdok, of the influential Hartman-Perdok theory, also known as the Periodic Bond Chain (PBC) theory, which describes how the internal atomic structure of a crystal dictates its external shape.
Early Life and Education
Piet Hartman was born in 1929. He pursued his higher education in the Netherlands, specializing in geology and crystallography, which laid the foundation for his future research in crystal physics and mineral morphology.Career and Research
Hartman spent a significant part of his academic career at Leiden University in the Netherlands, where he conducted extensive research in crystallography and mineralogy. His primary scientific interest lay in unraveling the mechanisms that govern how crystals form and grow into their characteristic external shapes.In the 1950s, in collaboration with W.G. Perdok, Hartman developed the groundbreaking Hartman-Perdok theory. This theory provided a new framework for predicting crystal morphology based on the crystal's internal atomic structure. It introduced the concept of "Periodic Bond Chains" (PBCs), which are continuous chains of strong chemical bonds running through the crystal structure in specific crystallographic directions.
According to the Hartman-Perdok theory, crystal faces can be classified into three types based on their interaction with PBCs:
- F-faces (Flat faces): These faces grow slowly and are typically large and well-developed on the crystal. They contain at least two non-parallel PBCs within their plane.
- S-faces (Stepped faces): These faces grow at an intermediate rate and are less developed. They contain only one PBC in their plane.
- K-faces (Kinked faces): These faces grow very rapidly and rarely appear on the external morphology of a crystal. They contain no PBCs within their plane.
This theoretical framework allowed scientists to predict the habit (the characteristic external shape) of a crystal from its known internal atomic arrangement, revolutionizing the study of crystal growth. The Hartman-Perdok theory has found broad application across various fields, including mineralogy, materials science, and pharmaceutical research, aiding in the understanding and control of crystallization processes.
Legacy
Piet Hartman's work, particularly the Hartman-Perdok theory, has left a profound and lasting impact on crystallography and materials science. The theory remains a cornerstone in the study of crystal growth and has influenced numerous subsequent theories and experimental investigations. His contributions helped to establish a crucial link between the microscopic atomic structure and the macroscopic morphology of crystals, significantly enhancing the ability to predict and manipulate crystal properties. He passed away in 2021, leaving behind a legacy of fundamental insights into the nature of crystalline materials.See Also
- Crystal growth
- Crystallography
- Mineralogy
- W.G. Perdok