Negative values for weight percentage or atomic percentage of compositional elements in EDS analysis are not physically meaningful and may indicate errors in the analysis or calculation. It is possible that there was a miscalibration of the EDS detector or incorrect assumptions were made during the quantitative analysis process.

However, the existence of the element from XRD analysis and elemental mapping images indicates that the element is present in the sample. Therefore, it is important to investigate and resolve the discrepancy between the EDS results and other analytical techniques.

To address this issue, it may be necessary to carefully review the EDS data and analysis process to identify any errors or inconsistencies. It may also be helpful to compare the EDS data with other analytical techniques, such as X-ray photoelectron spectroscopy (XPS) or Auger electron spectroscopy (AES), to corroborate the results and identify potential sources of error.

Overall, it is important to carefully consider and evaluate all available data to obtain a comprehensive understanding of the sample's composition and properties.

Negative sign means absence of element (usually because of poor understanding of the method by operator). And "XRD analysis and the elemental mapping" usually cannot prove presence of an element. Use spectra to make a qualitative analysis before conducting a quantitative one.

The weight percentage of an element is the weight of that element measured in the sample divided by the weight of all elements in the sample multiplied by 100.

The atomic percentage is the number of atoms of that element, at that weight percentage, divided by the total number of atoms in the sample

-ve sign means absence of element (usually because of poor understanding of the method by operator). And "XRD analysis and the elemental mapping" usually cannot prove presence of an element. Use spectra to make a qualitative analysis before conducting a quantitative one.