### DynamicMatrix_CH4

Posted:

**Sat May 23, 2020 11:10 am**Dear Dr.Graeme

I am trying to use dynamic matrix to get vibratioonal frequencies for some simple molecules in box.

I started with methane relaxation at PREC= High ,then followed by dynamic matrix calculations (files attached).However,the imaginary frequencies persist even after increasing the accuracy and box size (In fact when I increase the box size the number of imaginary frequency increase from 3 to 8 which was a bit strange):

57.266885 cm^{-1} ... 1

3.407140 cm^{-1} ... 1

2.811486 cm^{-1} ... 1

1.643336 cm^{-1} ... 1

1.425706 cm^{-1} ... 1

0.739629 cm^{-1} ... 1

0.149094 cm^{-1} ... 1

0.000025 cm^{-1} ... 1

5.644886 cm^{-1} ... 0

1281.384962 cm^{-1} ... 0

1282.428479 cm^{-1} ... 0

1501.560956 cm^{-1} ... 0

2950.633396 cm^{-1} ... 0

3076.440907 cm^{-1} ... 0

3078.811713 cm^{-1} ... 0

Your kind advice is appreciated!

Regards,

Omran

I am trying to use dynamic matrix to get vibratioonal frequencies for some simple molecules in box.

I started with methane relaxation at PREC= High ,then followed by dynamic matrix calculations (files attached).However,the imaginary frequencies persist even after increasing the accuracy and box size (In fact when I increase the box size the number of imaginary frequency increase from 3 to 8 which was a bit strange):

57.266885 cm^{-1} ... 1

3.407140 cm^{-1} ... 1

2.811486 cm^{-1} ... 1

1.643336 cm^{-1} ... 1

1.425706 cm^{-1} ... 1

0.739629 cm^{-1} ... 1

0.149094 cm^{-1} ... 1

0.000025 cm^{-1} ... 1

5.644886 cm^{-1} ... 0

1281.384962 cm^{-1} ... 0

1282.428479 cm^{-1} ... 0

1501.560956 cm^{-1} ... 0

2950.633396 cm^{-1} ... 0

3076.440907 cm^{-1} ... 0

3078.811713 cm^{-1} ... 0

Your kind advice is appreciated!

Regards,

Omran