equilibrium angle for SHAKE taken from angle table file

We are trying to use SHAKE in conjunction with angle_style table since we use many coarse grained models that involve tabulated potentials for all interactions.

There is an option to specify an equilibrium angle in the table data file via the EQ keyword. The examples in the manual suggest that the angle is give in degrees (e.g.,“N 181 FP 0 0 EQ 90.0” from the online manual.) However, my tests suggest that it wants angles in radians instead.

For example, when I tried to simulate SPC/E with “EQ 109.47”, the actual equilibrium angle that it seems to try to satisfy is 152 degrees, which I realized is 109.47 radians modulo pi. (This was only after turning off kspace which kept giving atoms out of box errors presumably due to the mismatch between input coordinates and the constraints.) When I used “EQ 1.9106” (ie the angle in radians), everything worked fine.

Does this seem correct? Just realized I am using an older build, so perhaps this was fixed in a later one?

Scott

We are trying to use SHAKE in conjunction with angle_style table since we use many coarse grained models that involve tabulated potentials for all interactions.

There is an option to specify an equilibrium angle in the table data file via the EQ keyword. The examples in the manual suggest that the angle is give in degrees (e.g.,“N 181 FP 0 0 EQ 90.0” from the online manual.) However, my tests suggest that it wants angles in radians instead.

your observation is correct. the conversion from degrees to radians is missing the source code for angle style table. it will be corrected in the next LAMMPS patch.

axel.