Dear all, As another example of using dwa-algorithm I tried to run 3D case in trap. The relevant part of "model.xml" is: <SITETERM site="i"> <PARAMETER name="mu#" default="mu"/> <PARAMETER name="U#" default="U"/> <PARAMETER name="K#" default="K"/> -mu#*n(i)+U#*n(i)*(n(i)-1)/2+K#*n(i)*((x-(L-1)/2)^2+(y-(L-1)/2)^2+(z-(L-1)/2)^2) </SITETERM> which works with both worm and dwa. But suppose I want a QUARTIC trap and not harmonic so I modify to <SITETERM site="i"> <PARAMETER name="mu#" default="mu"/> <PARAMETER name="U#" default="U"/> <PARAMETER name="K#" default="K"/> -mu#*n(i)+U#*n(i)*(n(i)-1)/2+K#*n(i)*((x-(L-1)/2)^2+(y-(L-1)/2)^2+(z-(L-1)/2)^2)^2 </SITETERM> Note that the only difference is a power 2 on squared radius. Worm manages fine. Dwa gives error message "Cannot evaluate y" What I am doing wrong? Is the failure of dwa due to an additional power 2 (since "dwa" in polish means "two")? I know the answer - dwa fails for any power different than 1.... Help appreciated best kuba Jakub Zakrzewski Zakład Optyki Atomowej, Instytut Fizyki im. Mariana Smoluchowskiego, UJ ul. Lojasiewicza 11, 30-348 Kraków, Poland +48-12-6644555, fax +48126644905 http://chaos.if.uj.edu.pl/~kuba