Your question is incorrect. Subject is part (singular) verb is are (plural). Your subject and verb should agree in number.
You also need to understand better how to use articles (a, an, the). Your writing will improve if you start to use them.
As to the part in bold: To my ear, good accuracy is redundant. Accuracy is always 'good' in scientific work. There's no such thing as 'bad' accuracy. We may, however, speak of a high degree of accuracy, but I'm not sure it would be appropriate here.
I don't know what is meant by "semi-empirical formulas" in this situation. It's not clear to me how something could be semi empirical.
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