EXCALIBR II
Abstract
The computer program EXCALIBR (Bloss and Riess, 1973; Bloss, 1981, p. 202) has been rewritten and markedly improved. Like EXCALIBR, EXCALIBR II solves optical extinction data, as determined with a spindle stage, and determines the optic axial angle 2V and the orientation of the crystal's optical indicatrix. EXCALIBR II uses a modification to Joel's equation as a means of obtaining the optic axes of a crystal. The new algorithm eliminates the need to solve the extinction data, quartet by quartet, as the first step towards finding a solution, as required by EXCALIBR. Furthermore, EXCALIBR II successfully solves extinction data where one optic axis of a biaxial crystal is 90° to the spindle axis, an orientation that had thwarted its predecessor. EXCALIBR II also accurately determines the optical indicatrix orientation for uniaxial crystals. The new program runs 10 times faster than EXCALIBR. In addition, creating data files is simplified by free-formatted input.
After solving extinction data for several different wavelengths and/or temperatures, EXCALIBR II calculates the angular change of each optic direction with wavelength and/or temperature along with the error on the angle. Using a simple t-test, it then computes a p-value to aid in the decision as to whether the optical direction truly exhibits dispersion. This is a more valid and sensitive procedure than the χ2 test used by EXCALIBR, particularly because the covariance in each optic vector's coefficients are taken into consideration and the results are invariant to the vector's orientation.
Articles in the same Issue
- The crystal structure of 7-hydroxy-4′-methoxyisoflavone
- The structures of dihydrophotoisodrin acetate and a dihydrophotoisodrin-dichloromethine addition product
- Structure of Be(IO3)2 · 2HIO3 · 6H2O
- EXCALIBR II
- The rutile structure of Al1−x□xO1−3xF1+3x, x = 0.0886
- Crystal and molecular structures of two N-derivatives of Cα,α-diethylglycine*
- Metal coordination in bis(metiamide)bis(isothiocyanato)cobalt(II) by powder X-ray diffraction
- Oxygen content and ordering in YBa2(Cu1−xMx)3O7−y (M = Au, Fe, Ga)
- Crystal and molecular structures of two N-carboxy anhydrides of Cα,α-disubstituted glycines*
- Structure and conformation of photosynthetic pigments and related compounds. 1. Methyl mesopyropheophorbide a
- Crystal and molecular structure of N-ethyl-1,8-naphthalimide
- Modelling the structures of La2NiO4
- Crystal structure of magnesium ultraphosphate, MgP4O11
- Crystal structure of hexacaesium triantimonidogallate, Cs6InSb3
- Crystal structure of hexarubidium triantimonidoaluminate, Rb6AlSb3
- Crystal structure of 5,6,7,8-tetrahydro-4H-cyclohepta[c]isothiazolio-(4-methyl)-benzamidate, C16H18N2OS
- Crystal structure refinement of bis-homo(dihydro)tetraaza[14]annulene bis(hydroperchlorate), C12H16N4(HCIO4)2
- Crystal structure of trans-bis(acetonitrile)-bis(1,2-bis(diphenylphosphino)ethane)iron(II)-bis-(tetrafluoroborate) bis(dichloromethane), (CH3CN)2(C26H24P2)2Fe(BF4)2(CH2Cl2)2
- Crystal structure refinement of chlorocarbonyl(sulfur dioxide)-bis(triphenylphosphine)-iridium, IrCl(CO)(SO2)(P(C6H5)3)2
- Crystal structure of N-tert.-butyloxycarbonyl-D-alanine benzylamide, C15H22N2O3
- Crystal structure of 10,10′-diphenyl-9,9′-bianthryl, (C6H5)(C14H8)2(C6H5)
- Crystal structure of 9,9′-bianthryl, (C14H9)2
- Crystal structure of 9-p-tolylanthracene, (C14H9)(C6H4)CH3
- Crystal structure of di-9-anthrylmethane, (C14H9)CH2(C14H9)
- Crystal structure of 9-(9-anthrylmethylidene)9,10-dihydroanthracene, (C14H10)CH(C14H9)
- Crystal structure of 9,10-diphenylanthracene, (C6H5)(C14H8)(C6H5)
- Crystal structure of ytterbium nickel dialuminium, YbNiAl2 with MgCuAl2 type
Articles in the same Issue
- The crystal structure of 7-hydroxy-4′-methoxyisoflavone
- The structures of dihydrophotoisodrin acetate and a dihydrophotoisodrin-dichloromethine addition product
- Structure of Be(IO3)2 · 2HIO3 · 6H2O
- EXCALIBR II
- The rutile structure of Al1−x□xO1−3xF1+3x, x = 0.0886
- Crystal and molecular structures of two N-derivatives of Cα,α-diethylglycine*
- Metal coordination in bis(metiamide)bis(isothiocyanato)cobalt(II) by powder X-ray diffraction
- Oxygen content and ordering in YBa2(Cu1−xMx)3O7−y (M = Au, Fe, Ga)
- Crystal and molecular structures of two N-carboxy anhydrides of Cα,α-disubstituted glycines*
- Structure and conformation of photosynthetic pigments and related compounds. 1. Methyl mesopyropheophorbide a
- Crystal and molecular structure of N-ethyl-1,8-naphthalimide
- Modelling the structures of La2NiO4
- Crystal structure of magnesium ultraphosphate, MgP4O11
- Crystal structure of hexacaesium triantimonidogallate, Cs6InSb3
- Crystal structure of hexarubidium triantimonidoaluminate, Rb6AlSb3
- Crystal structure of 5,6,7,8-tetrahydro-4H-cyclohepta[c]isothiazolio-(4-methyl)-benzamidate, C16H18N2OS
- Crystal structure refinement of bis-homo(dihydro)tetraaza[14]annulene bis(hydroperchlorate), C12H16N4(HCIO4)2
- Crystal structure of trans-bis(acetonitrile)-bis(1,2-bis(diphenylphosphino)ethane)iron(II)-bis-(tetrafluoroborate) bis(dichloromethane), (CH3CN)2(C26H24P2)2Fe(BF4)2(CH2Cl2)2
- Crystal structure refinement of chlorocarbonyl(sulfur dioxide)-bis(triphenylphosphine)-iridium, IrCl(CO)(SO2)(P(C6H5)3)2
- Crystal structure of N-tert.-butyloxycarbonyl-D-alanine benzylamide, C15H22N2O3
- Crystal structure of 10,10′-diphenyl-9,9′-bianthryl, (C6H5)(C14H8)2(C6H5)
- Crystal structure of 9,9′-bianthryl, (C14H9)2
- Crystal structure of 9-p-tolylanthracene, (C14H9)(C6H4)CH3
- Crystal structure of di-9-anthrylmethane, (C14H9)CH2(C14H9)
- Crystal structure of 9-(9-anthrylmethylidene)9,10-dihydroanthracene, (C14H10)CH(C14H9)
- Crystal structure of 9,10-diphenylanthracene, (C6H5)(C14H8)(C6H5)
- Crystal structure of ytterbium nickel dialuminium, YbNiAl2 with MgCuAl2 type
