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h [2009/08/06 14:38] – created clare | h [2022/11/03 15:08] (current) – external edit 127.0.0.1 |
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| **[//hkl_plane// $hkl] ...** |

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| Used by the OpenGL viewer to display hkl planes, see the CeO2.STR file in the “Rigid” directory. Here are some examples: |

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| str… |

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| hkl_plane 1 1 1 |

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| hkl_plane “2 -2 0” |

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| ** [//grs_interaction// [//from_N// #] [//to_N// #] [//no_self_interaction//] $site_1 $site_2 qi # qj # N E]...** |

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| Defines a GRS interaction with a name of N between [[#k142|sites identified]] by $site_1 and $site_2. E represents the GRS interaction equation that can be a function of R, which returns the distance in Angstroms between two atoms; these distances are updated when dependent fractional atomic coordinates are modified. The name of the //grs_interaction// N can be used in equations and in particular penalty equations. |

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| When either //from_N// or //to_N// are defined, the interactions between $site_1 and $site_2 are sorted by distance and only the interactions between the //from_N// and //to_N// are considered. |

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| //no_self_interaction// prevents any interactions between equivalent positions of the same site. This is useful when a general position is used to describe a special position. |

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| //qi// and //qj// corresponds to the valence charges used to calculate the Coulomb sum for the sites $site_1 and $site_2 respectively. |

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| //grs_interaction// is typically used for applying electrostatic restraints in inorganic materials. The GRS_Interaction macro simplifies the use of //grs_interaction//. |

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| **[//hat// E [//num_hats// #] ]...** |

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| Defines the X-axis size of an impulse function that is convoluted into phase peaks. //num_hats// corresponds to the number of hats to be convoluted. //num_hats// is set to 1 by default. //hat// is used for example by the Slit_Width and Specimen_Tilt macros. |

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| **[//hkl_Is//]...** |

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| **[//lp_search// !E]** |

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| **[//I_parameter_names_have_hkl// $start_of_parameter_name]** |

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| **[//hkl_m_d_th2// # # # # # # I E]...** |

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| Defines a phase type that uses hkls for generating peak positions. |

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| //lp_search// uses a new indexing algorithm that is independent of d-spacing extraction; lp-search-pbso4.inp demonstrates its use. lp_search minimizes on a new figure of merit function that gives a measure of correctness for a particular set of lattice parameters. More specifically the figure of merit function assigns parts of the diffraction pattern to peaks and then sums the absolute values of the products of the diffraction intensities multiplied by the distance to the peaks: |

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| <sub>{{techref_files:image158.gif?213x39}}</sub>where the summation in ‘j’ is over the calculated Bragg positions 2//q<sub>0</sub>// and the summation in ‘i’ is over part of the diffraction pattern such that (2//q//<sub></sub><sub>0, j-1</sub> + 2//q//<sub></sub> <sub>0, j</sub>.)/2 < 2//q//<sub>i</sub> < (2//q//<sub></sub> <sub>0, j+1</sub> + 2//q//<sub></sub><sub>0, j</sub>.)/2. The method avoids difficulties associated with extracting d-spacings from complex patterns comprising heavily overlapped lines; the primary difficulty being that of ascertaining the number of lines present. |

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| //I_parameter_names_have_hkl// gives generated Intensity parameters a name starting with $start_of_parameter_name and ending with the corresponding hkl. |

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| //hkl_m_d_th2//: The numbers after the keyword //hkl_m_d_th2// define h k l m d and 2q values, where |

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| h, k, l : Miller indices |

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| m : multiplicity. |

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| //d// and th2 : d and 2q values (not used by). |

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| //I// : Peak intensity parameter before applying any //scale_pks//. |

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| If no //hkl_m_d_th2// keywords are defined then the hkls are generated using the space group; the generated //hkl_m_d_th2// details are appended at the end of the //space_group// keyword on refinement termination. Intensity parameters are given an initial starting value of 1. If the Le Bail keyword is not defined then the intensity parameters are given the unique code of @ . |

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| For example, the following input segment: |

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| xdd quartz.xdd |

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| ... |

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| hkl_Is |

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| Hexagonal(4.91459, 5.40603) |

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| space_group P_31_2_1 |

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| will generate the following OUT file: |

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| xdd quartz.xdd |

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| ... |

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| hkl_Is |

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| Hexagonal(4.91459, 5.40603) |

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| space_group P_31_2_1 |

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| load hkl_m_d_th2 I |

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| { |

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| 1 0 0 6 4.25635 20.85324 @ 3147.83321 |

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| 1 0 1 6 3.34470 26.62997 @ 8559.23955 |

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| 1 0 -1 6 3.34470 26.62997 @ 8559.23955 |

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| ... |

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| } |

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| The Create_hklm_d_Th2_Ip_file macro creates an hkl file listing from structures in the same format as the "load hkl_m_d_th2 I" as shown above. Even though the structure would have no sites, the //weight_percent// keyword can still be used; it will use whatever value is defined by //cell_mass// in order to calculate //weight_percent//. |

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| **[//hkl_Is_from_hkl4//]** |