Contracting entities may use a negotiated procedure without prior call for competition in the following cases:

(a) where no tenders or no suitable tenders or no requests to participate or no suitable requests to participate have been submitted in response to a procedure with a prior call for competition, provided that the initial conditions of the contract are not substantially altered;

A tender shall be considered not to be suitable where it is irrelevant to the contract, being manifestly incapable, without substantial changes, of meeting the contracting entity's needs and requirements as specified in the procurement documents. A request for participation shall be considered not to be suitable where the economic operator concerned is to be or may be excluded pursuant to Articles 78(1) or 80(1), or does not meet the selection criteria laid down by the contracting entity pursuant to Articles 78 or 80;

(b) where a contract is purely for the purpose of research, experiment, study or development, and not for the purpose of securing a profit or of recovering research and development costs, and insofar as the award of such contract does not prejudice the competitive award of subsequent contracts which do seek, in particular, those ends;

(c) where the works, supplies or services can be supplied only by a particular economic operator for any of the following reasons:

(i) the aim of the procurement is the creation or acquisition of a unique work of art or artistic performance;