ABSTRACT
Around 1900 most questions about the nature of chemical bonding and a fortiori about the cohesion of solids were unanswered. This was even true for the ‘simple’ case of the hydrogen molecule which was to remain a mystery until 1927 (Heitler and London)! All attempts to develop a convincing theory of the cohesion of solids such as carbon (graphite or diamond), copper or ice were doomed to failure whilst the essential tool of quantum mechanics was missing.
