l_max

It sets the angular descriptors, see Sect. II.C of [Fan2022b]. The syntax is:

l_max <l_max_3b> {<has_q_222> <has_q_1111> <has_q_112> <has_q_123> <has_q_233> <has_q_134>}

where l_max_3b sets the limit for the three-body descriptors, has_q_222, has_q_112, has_q_123, has_q_233, and has_q_134 optionally specify which four-body descriptors are used, and has_q_1111 specifies if the five-body descriptor is used.

\(l_\mathrm{max}^\mathrm{3b}\) can take values from 2 to 8, and has_q_222, has_q_1111, has_q_112, has_q_123, has_q_233, and has_q_134 can be 0 (not to use) or 1 (to use).

The default values are:

l_max 4 1
l_max 4 1 0 0 0 0 0 # equivalent way to write it

The five-body descriptor switch has_q_1111 is only provided for backward compatibility. This five-body descriptor is equivalent to the square of two three-body descriptors and thus does not provide new information. Its use is strongly discouraged.

The new four-body descriptors (q_112, q_123, q_233, and q_134) have not been comprehensively tested, and should be used with caution. More suggestions on this will be made in a future version.