Titanium　oxide　films　of　various　composition　grown　on　a　Mo(112)　metal　substrate　have　been　investigated　with　the　help　of　first　principles　density　functional　theory　plane　wave　calculations　using　the　PW91　functional.　We　show　that　at　the　experimental　pressure　and　temperature　conditions　used　to　grow　the　films　a　structure　with　composition　TiO3　is　preferred.　This　conclusion　is　based　on　the　thermodynamic　analysis　of　the　film　stability　as　a　function　of　the　oxygen　partial　pressure　and　is　corroborated　by　the　comparison　of　computed　and　measured　properties　like　scanning　tunneling　microscopy　images,　vibrational　modes,　and　core　level　binding　energies.　The　electronic　properties　of　the　films　are　discussed　in　terms　of　density　of　states,　charge-transfer　at　metal/oxide　interfaces,　and　work　function　changes.