**OPTImize B****{ xrefin-optimize-B-statement } END**is an xrefin statement. Action takes place as soon as the END statement is issued.**xrefin-optimize-B-statement:==**-
**ASIGma=selection=real**- specifies the target standard deviation between B-factors of selected atoms connected by an angle . Multiple specification is possible ( default: none).
**BFMIn=real**- specifies the minimum B-factor allowed ( default: 2.0 Å).
**BSIGma=selection=real**- specifies the target standard deviation between B-factors of selected bonded atoms . Multiple specification is possible (default: none).
**DROP=real**- is the initial expected drop in energy ( default: 10.0).
**NSTEp=integer**- is the number of conjugate gradient steps ( default: 0).
**RWEIght=real**- is the weight for B-factor restraints. If negative, weight will be set automatically. If zero, no restraints will be computed (default: -1).
**TOLErance=real**- is the gradient that forces exit ( default: 0).