کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5418367 | 1506945 | 2008 | 8 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
On the calculation of 15N chemical shifts using linear regression formulae. A performance comparison of different methods
دانلود مقاله + سفارش ترجمه
دانلود مقاله ISI انگلیسی
رایگان برای ایرانیان
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: On the calculation of 15N chemical shifts using linear regression formulae. A performance comparison of different methods On the calculation of 15N chemical shifts using linear regression formulae. A performance comparison of different methods](/preview/png/5418367.png)
چکیده انگلیسی
The calculation of NMR chemical shifts using linear regression formulae is revisited in the present work. 15N chemical shifts are considered as a test case. Mean unsigned errors of 4.8, 5.4 and 7.6Â ppm are found for the B3LYP/6-31G(d)//B3LYP/6-31G(d), B3LYP/6-311+G(2d,p)//B3LYP/6-31G(d) and HF/6-31G(d)//B3LYP/6-31G(d) levels of theory, respectively, which are much more accurate than chemical shifts calculated by subtracting theoretical magnetic isotropic shieldings from the reference nitromethane. Moreover, the economical HF/6-31G(d)//B3LYP/6-31G(d) method is found to be about 15 times faster than the rather expensive B3LYP/6-311+G(2d,p)//B3LYP/6-31G(d) level of theory but only 2.5 times faster than B3LYP/6-31G(d)//B3LYP/6-31G(d). Our results indicate that the B3LYP/6-31G(d)//B3LYP/6-31G(d) level of theory constitutes an adequate compromise between accuracy and computational cost for 15N chemical shifts calculation using a linear regression formula.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Molecular Structure: THEOCHEM - Volume 856, Issues 1â3, 15 May 2008, Pages 1-8
Journal: Journal of Molecular Structure: THEOCHEM - Volume 856, Issues 1â3, 15 May 2008, Pages 1-8
نویسندگان
Carlos A. Franca, Reinaldo Pis Diez, Alicia H. Jubert,