Nitrogen as the best interstitial dopant among<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>X</mml:mi><mml:mo>=</mml:mo><mml:mi mathvariant="normal">B</mml:mi></mml:mrow></mml:math>, C, N, O, and F for strong permanent magnet<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>NdFe</mml:mi><mml:mn>11</mml:mn></mml:msub><mml:mi>Ti</mml:mi><mml:mi>X</mml:mi></mml:mrow></mml:math>: First-principles study
Physical review. B, Condensed matter and materials physics