[gmx-users] soft core potential

[Erik Lindahl]

Hi,

As a said in the last paragraph - if c6=0 there isn't any dispersion 
interaction at all, neither distorted or normal.

Just go back to the definition in section 4.3.1 of the manual. 
Interactions are additive, so the formula holds true for the individual 
dispersion and repulsion parts of the Lennard-Jones potential.

Cheers,

Erik



On Monday, October 6, 2003, at 01:11 PM, Ilya Chorny wrote:

> I don't understand. I'm am only interested in what happens to the
> softcore distortion if C6 = 0. In  this case is sigma^6 = sc_sigma^6.
>
> Thanks
>
> Ilya
>
>
>
> On Mon, 2003-10-06 at 12:48, Erik Lindahl wrote:
>> Hi,
>>
>> The softcore sigma value is used for the softcore distortion/scaling 
>> of
>> the potential, not the actual interaction.
>>
>> If both c6 & c12 are positive, it is calculated from sigma^6=c12/c6,
>> otherwise the default value is used.
>>
>>
>> Hence, If you have c6=0 for a particular interaction, the dispersion
>> part will be zero no matter what the sc_sigma value is.
>>
>> Cheers,
>>
>> Erik
>>
>>
>> On Monday, October 6, 2003, at 12:14 PM, Ilya Chorny wrote:
>>
>>> Hi I was wondering if anybody has an answer to my question?
>>>
>>> Ilya
>>>
>>> On Thu, 2003-10-02 at 10:11, Ilya Chorny wrote:
>>>> Hello
>>>>
>>>> In the manual it says that by default sc_sigma = .3 nm.
>>>> What C6 value does this correspond to. More specifically I have C6 
>>>> set
>>>> to 0.0. What will gromacs use as the C6 value in the soft core
>>>> potential.
>>>>
>>>> Thanks
>>>>
>>>> Ilya
>>>
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