# Reduce content of unit cell to asymmetric unit. Atom types, B factors and occupancies are restricted to those corresponding to positions in the asymmetric unit, if the input space group (SG) is P-1. Otherwise they are only sorted according to increasing atom positions. If the starting positions do not correspond to a properly symmetry-expanded set, then a warning is issued. If no symmetry is used (P1) the starting set is forced to have values inside the unit cell and it is sorted according to increasing atom positions. ```r reduce_to_asu(adata, SG = NULL) ``` ## Arguments - `adata`: A named list, normally obtained through the use of function `read_x`. The list names correspond to different object types: * a. Real numeric. The size of the unit cell. * SG. Character string. Space group symbol; either "P1" or "P-1" * x0. Vector of real numerics indicating the expanded atomic positions in the unit cell. * Z. Vector of integers indicating the expanded atomic numbers for all atoms in the unit cell. * B. Vector of real numerics indicating the expanded B factors for all atoms in the unit cell. * occ. Vector of real numerics indicating the expanded occupancies for all atoms in the unit cell. - `SG`: 2-letters character string. There are only two symmetries possible when working within 1D crystallography, P1 (no symmetry) and P-1 (inversion through the origin). SG can be either "P1" or "P-1" for this function. Default is NULL, in which case the space group is assumed to be equal to the one of the input structure. ## Returns A named list with the following elements: * x0. Vector of real numerics indicating the reduced atomic positions in the asymmetric unit. * Z. Vector of integers indicating the reduced atomic numbers for all atoms in the asymmetric unit. * B. Vector of real numerics indicating the reduced B factors for all atoms in the asymmetric unit. * occ. Vector of real numerics indicating the reduced occupancies for all atoms in the asymmetric unit. ## Examples ```r # Asymmetric unit includes 4 atoms between 0 and a/2, 1 in special position a <- 10 SG <- "P-1" x0 <- c(1,2,4,5) Z <- c(6,8,6,16) B <- c(1,1.2,1.1,0.8) occ <- c(1,1,1,0.5) adata <- standardise_sdata(a,SG,x0,Z,B,occ) ltmp <- expand_to_cell(adata) print(ltmp) # Positions, atomic numbers, etc. have doubled # Now these expanded values are used as input for reduction ltmp2 <- reduce_to_asu(ltmp) # Compare print(x0) print(ltmp2$x0) # SG is "P1" a <- 16 SG <- "P1" x0 <- c(1,2,7,9,12,16) Z <- c(6,6,8,8,7,6) B <- c(0,0,0,0,0,0) occ <- c(1,1,1,1,1,1) adata <- standardise_sdata(a,SG,x0,Z,B,occ) ltmp3 <- reduce_to_asu(adata) print(ltmp3) # Now all positions are inside the unit cell ```

reduce_to_asu function