The Greek aim is to get a strategic deal on the debt, and to avoid a short term bank collapse and default – but they can only do this by taking their negotiating partners to the brink.
If negotiations fail, and Grexit happens, I would expect the sequence to be:
(i) Failure to agree a bridging program triggers more rapid capital flight
(ii) ECB signals decisively it will pull Emergency Lending Assistance, triggering a bank run and bank closures, probably between 18 February and 28 February,
(iii) Capital controls, with Greece effectively operating as semi-detached member of the Eurozone;
(iv) default on debts to European sovereigns as they come up for refinancing
(v) the possible issuance of alternative currency, or paper acting as such in the banking system.