# ESP (Electrostatic Potential in NWChem)

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 Matrix2017 Member Profile Send PM
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 5:33:02 AM PDT - Tue, Jul 18th 2017 I am concerned about the units of the ESP in NWChem. Consider the data on HF in the output file: ```1 a.u. = 9.07618 esu/cm ( or statvolts ) ``` Point X Y Z Total Potential(a.u.) Diamagnetic shielding(a.u.) ``` 1 F 0.00000 0.00000 -0.08806 -26.551580 27.123542 2 H 0.00000 0.00000 1.66031 -0.905417 6.053075 ``` Now consider the same data from Gamess on the same molecule: electric potential 1 a.u. = 9.076814E-02 esu/cm ``` Total Potential (a.u.) Diamagnetic shielding (a.u.) F -26.554587 27.126252 H -0.902754 6.047740 ``` Is it possible that NWChem has an error in the conversion factor from a.u. to esu/cm? Edited On 1:20:11 PM PDT - Tue, Jul 18th 2017 by Matrix2017

 Matrix2017 Member Profile Send PM
 Just Got Here Threads 2 Posts 3
 1:17:39 PM PDT - Tue, Jul 18th 2017 Proof of an error using an H atom The potential energy of H in the ground state is exactly 27.2116 Volts The calculated potential energy = constant * 299.7925 * the calculated value in A.U. The value, 299.7925 is the conversion from esu/cm to volts where esu / cm are the units of the electrostatic potential energy in NWChem or Gamess. constant(NWChem) = 9.07618, constant(Gamess)=0.09076814 V(Gamess) = 0.09076814 * 299.7925 * (-0.990160) = -26.943845 Volts V(NWChem) = 9.07618 * 299.7925 * (-0.990745) = -2695.788108 Volts V(Exact) = 27.2116 Volts The results suggest that NWChem may have an error in the conversion constant.

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