Abstract
The structure determination from laboratory X-ray powder diffraction data of oxamic acid, a derivative of the biologically active oxalic acid and the simplest organic acid containing an amide group, is presented in this contribution. An energy minimization analysis by DFT-D was carried out. The structure was determined with the program TALP and refined by the Rietveld method with GSAS-II in space group Cc (No. 9). The final unit-cell parameters are a = 9.4989 (6), b = 5.43796 (9), c = 6.8637 (9) Å β = 107.152 (5)° V = 338.772 (10) Å3, Z = 4. The refinement converged to the figures of merit: Re = 0.01674, Rp = 0.03270, Rwp = 0.05652 and GoF = 3.378 with a good fit between the calculated pattern of the structural model and the experimental pattern. The DFT-D calculations show an excellent reproduction of the experimental structure, validating the correctness of the structure. The non-centrosymmetric nature of the structure was confirmed by SHG measurements. In the crystal structure, the molecules are close to planar and form a complex 2D hydrogen-bonding pattern based on the cyclic amide-acid heterosynthon.
Original language | English |
---|---|
Pages (from-to) | 310-316 |
Number of pages | 7 |
Journal | Journal of Molecular Structure |
Volume | 1177 |
DOIs | |
State | Published - Feb 5 2019 |
Funding
This work was supported by FONACIT-Venezuela , Grant LAB-97000821 . Avant-garde Materials Simulation is gratefully acknowledged for access to the GRACE software. A portion of this research used resources at the Spallation Neutron Source, which is a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The SHG measurements were conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. Access to the Cambridge Structural Database (CSD) was possible through the Frank H. Allen International Research & Education Programme (FAIRE) from the Cambridge Crystallographic Data Centre (CCDC). This work was supported by FONACIT-Venezuela, Grant LAB-97000821. Avant-garde Materials Simulation is gratefully acknowledged for access to the GRACE software. A portion of this research used resources at the Spallation Neutron Source, which is a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. The SHG measurements were conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility.
Keywords
- DFT-D calculations
- GSAS-II
- Oxamic acid
- SHG measurements
- Structure determination
- TALP